Kennedy Disease; X-linked Bulbospinal Neuropathy

Spinobulbar muscular atrophy (SBMA) is characterized by adolescent-onset mild androgen insensitivity (e.g., gynecomastia, small testes, oligo- or azoospermia) in males. This is followed by post-adolescent onset (age 20 – 50) proximal muscle weakness, fasciculations, and atrophy due to lower motor neuron degeneration. Eventually, most individuals with SBMA will have bulbar involvement. Life expectancy is not reduced. Carrier females are unaffected.

SBMA is caused by expansion of a CAG trinucleotide repeat in exon 1 of the androgen receptor (AR) gene on the X-chromosome. Inheritance is X-linked recessive. In general, repeat size roughly corresponds to the severity of disease and age of onset. Alleles in the AR gene are classified as:

• Normal: ≤ 34 repeats
• Questionable Significance: 35 repeats
  There is no consensus regarding the significance of an allele with 35 repeats
• Reduced Penetrance: 36 – 37 repeats
  It has been suggested that alleles with 36 or 37 repeats are reduced penetrance alleles, although this remains unclear.
• Full Penetrance: ≥ 38 repeats

1. Confirmation of diagnosis:
   1. In males with clinical features suggestive of SBMA.
2. Carrier Testing:
   1. Adult females at risk to be carriers of SBMA due to a family history. NB: Daughters of affected male individuals are obligate carriers of SBMA.
3. Prenatal testing (technically feasible, but not routinely performed – contact MGL to discuss):
   1. Male pregnancies at risk of SBMA. Prior to testing for SMBA, fetal sexing is performed; if the fetus is female, further testing is not indicated.
4. Presymptomatic testing:
   1. Adult males at risk of developing SBMA due to a family history. Predictive testing will only be performed following genetic counselling by a recognized genetic service.

The CAG repeat size is determined using an ABI genetic analyzer following fluorescence-based PCR amplification.

Blood: 4 mL EDTA is optimal (Minimum: 1 mL EDTA)
DNA: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth and ship to the address below. Samples should be shipped at room temperature with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays). 

Testing is only available to residents of Canada, except in very specific circumstances where testing is urgent or emergent.  Payment is not required when requests are made for individuals who are insured by Health Insurance BC (administered through the BC Medical Services Plan (MSP)) AND eligible for testing according to the test utilization guidelines / policy. If the individual undergoing testing is not insured by these providers or does not meet utilization guidelines or policy, please complete a billing form; testing will only commence after receipt of billing informationTest prices can be found here.

Molecular genetic testing is limited by the current understanding of the genome and the genetics of a particular disease, as well as by the method of detection used. This method will not detect all mutations (e.g., point mutations in the coding region of the gene, large genomic deletions, promoter mutations, regulatory element mutations). For some trinucleotide repeat disorders, repeat expansions have been described that cannot be amplified by PCR. Consideration should be given to this particularly in cases with severe clinical features or early onset; consult the on-service Molecular Geneticist to discuss specific repeat disorders.

For carrier/predictive testing due to family history, it is generally important to first document the gene mutation in an affected or carrier family member. This information should be provided to the laboratory for assessment of whether the assay is appropriate for detection of the familial mutation, and to aid in the interpretation of data.

In some cases, DNA alterations of undetermined or unclear clinical significance may be identified.

In certain scenarios of repeat size mosaicism, false negative results may occur. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

Rare single nucleotide variants or polymorphisms could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

A previous bone marrow transplant from an allogenic donor will result in molecular data that reflects the donor genotype rather than the recipient (patient) genotype. Consult the on-service Molecular Geneticist for approach to testing in such individuals.

Transfusions performed with packed red blood cells will generally not affect the outcome of molecular genetic testing. However, if there is no clinical urgency, the cautious approach is to wait one week post packed red cell transfusion before collecting a sample for genetic testing. Consult the on-service Molecular Geneticist as needed.

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.

Werdnig-Hoffmann Disease; Infantile Muscular Atrophy; Kugelberg-Welander Syndrome; Juvenile Muscular Atrophy; Proximal SMA

Spinal muscular atrophy (SMA) is an autosomal recessive condition characterized by progressive muscle weakness caused by the degeneration of anterior horn cells of the spinal cord and the brain stem nuclei. Onset ranges from before birth to young adulthood. Poor weight gain, sleep difficulties, pneumonia, scoliosis, and joint contractures are common complications. Subtypes include: SMA 0 (proposed name; also referred to as prenatal), with prenatal onset and severe joint contractures, facial diplegia, and respiratory failure; SMA 1, with onset before six months of age; SMA 2, with onset between six and 12 months; SMA3, with onset in childhood after 12 months; and SMA 4, with adult onset.

Two adjacent genes, SMN1 and SMN2, are associated with SMA. The two genes differ by only five base pairs and none of these base pair differences change the amino acids encoded by the genes. Nonetheless, the two genes do not encode identical proteins. SMN1 produces full-length transcripts while SMN2 primarily produces transcripts that lack exon 7 because one of the base pair changes in exon 7 disrupts SMN2 gene splicing.

SMN1 is the SMA disease gene. Approximately 95 – 98% of individuals with a clinical diagnosis of SMA are homozygous for an apparent deletion of exon 7 in SMN1. The remaining 2 – 5% are compound heterozygotes for an apparent deletion of exon 7 of SMN1 and an intragenic point mutation in SMN1.

The copy number of the SMN2 gene varies, ranging from zero to five. Although SMN2 does not produce the full length transcript with high efficiency, some full length transcript is produced. In some individuals with SMA who also have an increased copy number of the SMN2 gene, the small amount of full-length transcript generated SMN2 may help to produce a milder phenotype.

1. Confirmation of diagnosis:
   1. In individuals with clinical features suggestive of SMA.
2. Carrier testing:
   1. Adults at risk to be carriers of SMA due to a family history.
      NB: For the most accurate assessment of carrier status, please provide the results of SMN1 molecular analysis of the parents of the affected individual.
3. Prenatal testing (prenatal diagnosis requests are not normally accepted from physicians other than Medical Geneticists):
   1. Pregnancies at risk of SMA, where the parents have been confirmed by molecular analysis to each carry an SMN1 deletion.
      NB: If only one of the parents has been confirmed to be a carrier, contact the Molecular Geneticist on-service to discuss options.
4. Presymptomatic testing:
   1. Adults at risk of developing a milder form of SMA due to a family history confirmed to be due to SMN1 deletions.

The copy number of exons 7 and 8 of both the SMN1 and SMN2 genes is assessed by multiplex ligation-dependent probe amplification (MLPA) using the P060 probe mix (MRC-Holland).

Pregnancy-related/Prenatal

If pregnancy management will be altered, 3 weeks; otherwise, routine TAT.

Blood: 4 mL EDTA is optimal (Minimum: 1 mL EDTA)
DNA: NOT ACCEPTED

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth and ship to the address below. Samples should be shipped at room temperature with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays). 

Prenatal Specimens
Prenatal testing REQUIRES LABORATORY CONSULTATION PRIOR TO THE PROCEDURE and can only be ordered by a Medical Geneticist. Contact the laboratory at 604-875-2852 and choose the appropriate option for the Molecular Geneticist on service.
Chorionic Villi: 20 mg.
Direct Amniotic fluid: 25 mL collected in two separate tubes of equal volume.
Cultured Amniocytes: Two (2) 100% confluent T-25 flasks.

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth. Ship samples by overnight courier with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays) as follows:

• Villi – on wet ice or in media at room temperature
• Amniocytes, Amniotic fluid, DNA – at room temperature

Testing is only available to residents of Canada, except in very specific circumstances where testing is urgent or emergent.  Payment is not required when requests are made for individuals who are insured by Health Insurance BC (administered through the BC Medical Services Plan (MSP)) AND eligible for testing according to the test utilization guidelines / policy. If the individual undergoing testing is not insured by these providers or does not meet utilization guidelines or policy, please complete a billing form; testing will only commence after receipt of billing informationTest prices can be found here.

Molecular genetic testing is limited by the current understanding of the genome and the genetics of a particular disease, as well as by the method of detection used. This method will not detect all mutations (e.g., point mutations in the coding region, promoter mutations, and regulatory element mutations). In rare cases, a point mutation could be detected.

For carrier/predictive testing due to family history, it is generally important to first document the gene mutation in an affected or carrier family member. This information should be provided to the laboratory for assessment of whether the assay is appropriate for detection of the familial mutation, and to aid in the interpretation of data.

In some cases, DNA alterations of undetermined or unclear clinical significance may be identified.

Rare single nucleotide variants or polymorphisms could lead to false-negative results. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

A previous bone marrow transplant from an allogenic donor will result in molecular data that reflects the donor genotype rather than the recipient (patient) genotype. Consult the on-service Molecular Geneticist for approach to testing in such individuals.

Transfusions performed with packed red blood cells will generally not affect the outcome of molecular genetic testing. However, if there is no clinical urgency, the cautious approach is to wait one week post packed red cell transfusion before collecting a sample for genetic testing. Consult the on-service Molecular Geneticist as needed.

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.

Hemoglobin H Disease; Hydrops Fetalis; Alpha Thalassemia Minor; Alpha Thalassemia Trait; Thalassemia Intermedia; Cooley’s Anemia; Mediterranean Anemia; Beta Thalassemia Major; Beta Thalassemia Minor; Beta Thalassemia Trait; Sickle Cell Disease; Sickle Cell Anemia; Hemoglobin C Trait; Hemoglobin E Trait

Thalassemias and hemoglobinopathies are conditions affecting the quantity and functionality, respectively, of hemoglobin within red blood cells.

The thalassemias are the result of mutations that decrease or eliminate the production of individual globin chains of the hemoglobin tetramer.

The sickle cell disorders are hemoglobinopathies caused by specific point mutations in the β globin gene (hemoglobins S, C, and E) that result in structural abnormalities of the protein rather than decreased production.  The clinical features of the sickle disorders can be quite variable, depending in part on the particular number and combination of α globin mutations.

In addition, since both the α- and β-globin chains comprise the primary adult hemoglobin, the co-inheritance of β globin gene mutations (for either thalassemia or hemoglobinopathies) and α globin mutations (for thalassemia) further increases the clinical variability encountered in this group of disorders.

Alpha thalassemia

Alpha thalassemia typically results from deletion of one or more of the four α globin genes.  Rare point mutations may also contribute to the condition.

Beta thalassemia

Beta thalassemia results most commonly from point mutations that lead to a reduction or complete loss of protein synthesis from one or both β globin genes.

Sickling disorders

The sickling disorders are the result of single point mutations in the β globin gene that result in the production of abnormal β globin chains.  HbS, the hemoglobin that causes sickle cell disease when present in the homozygous state, is caused by a p.Glu6Val β globin substitution (c.20A>T).  HbC is caused by a p.Glu6Lys (c.19G>A) β globin substitution .  HbE is caused by a p.Glu26Lys (c.79G>A) β globin substitution.  Notably, the HbE mutation results in the activation of a cryptic donor splice site, resulting in a thalassemia phenotype when co-inherited with another beta thalassemia mutation.

Other hemoglobinopathies result from various combinations of alpha and/or beta globin mutations as well as the other globin chain genes.

A hematology profile, including CBC and hemoglobin electrophoresis/HPLC, must be performed prior to ordering molecular genetic testing for the hemoglobin disorders unless an individual has a clinical diagnosis of one of the hemoglobin disorders.  If hematology investigations require follow up with molecular genetic testing, then these tests may be ordered.

1. Confirmation of diagnosis: 
   1. Testing ordered by a hematologist as relevant to the clinical presentation of the patient; to confirm a suspected or known clinical diagnosis or clarify unusual hemoglobinopathy cases.
2. Carrier testing:
   1. When ordered by a hematologist: as relevant to the clinical presentation/management of disease of the patient.
   2. Pediatric patients: to aid in the discrimination of carrier status from iron deficiency anemia.
   3. Adults of reproductive age: as per the SOGC-CCMG clinical practice guideline (2008).
   4. Specific for alpha thalassemia:
      1. In adults of reproductive age when:
         1. Both members of the couple have beta thalassemia trait and they may also be at risk of conceiving a child with Hemoglobin Barts hydrops fetalis syndrome.
         2. One member of the couple has beta thalassemia trait and the other has hematology suggestive of alpha thalassemia trait (i.e. their pregnancy may also be at risk of Hb Barts/hydrops fetalis)
      2. NB: Carrier screening to determine the reproductive risk for HbH disease is NOT an indication for molecular genetic testing that is eligible for coverage by BC MSP unless one member of the couple has hematology consistent with alpha thalassemia trait and the other has HPLC findings consistent with the HBA2 Constant Spring or Quong Sze mutations.
3. Prenatal testing (prenatal diagnosis requests are not normally accepted from physicians other than Medical Geneticists):
   1. Pregnancies known to be at risk based on parental carrier screening or ultrasound findings.

Carrier screening to determine the reproductive risk for HbH disease is NOT an indication for molecular genetic testing for alpha thalassemia except where one member of the couple has hematology consistent with alpha thalassemia trait and the other has HPLC findings consistent with a pathogenic HBA1 or HBA2 mutation (for example, hemoglobin Constant Spring). Genetic counselling is required prior to testing for couples in this scenario.

Alpha thalassemia: Gap junction PCR analysis is carried out to detect the –SEA, -α20.5, –MED, –FIL, –THAI, -α3.7, and -α4.2 deletions. Bidirectional Sanger sequencing across the region of the alpha-2 gene (HBA2) that contains the Constant Spring (c.427T>C, p.*143GlnextX32) and Quong Sze (c.377T>C, p.Leu126Pro) mutations is not routinely performed, but is available in certain clinical scenarios; consult on-service Molecular Geneticist.

Beta thalassemia & Hemoglobins S, C, E: Bidirectional Sanger sequencing across all exons of the HBB gene and intron sequences flanking each exon (exon 1: c.-105 to c.92+10; exon 2: c.93-25 to c.315+25; exon 3: c.316-200 to c*110). 

HBA: NM_000517.4  The ‘A’ within the initiation codon, ATG, is designated as nucleotide number 1.

HBB: NM_000518.4  The ‘A’ within the initiation codon, ATG, is designated as nucleotide number 1.

Pregnancy-related/Prenatal

If pregnancy management will be altered, 3 weeks; otherwise, routine TAT.

Blood: 4 mL EDTA is optimal (Minimum: 1 mL EDTA)
DNA: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth and ship to the address below. Samples should be shipped at room temperature with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays).  

Prenatal Specimens
Prenatal testing REQUIRES LABORATORY CONSULTATION PRIOR TO THE PROCEDURE and can only be ordered by a Medical Geneticist. Contact the laboratory at 604-875-2852 and choose the appropriate option for the Molecular Geneticist on service.
Chorionic Villi: 20 mg.
Direct Amniotic fluid: 25 mL collected in two separate tubes of equal volume.
Cultured Amniocytes: Two (2) 100% confluent T-25 flasks.
DNA extracted from prenatal specimens: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth. Ship samples by overnight courier with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays) as follows:

• Villi – on wet ice or in media at room temperature
• Amniocytes, Amniotic fluid, DNA – at room temperature

A hematology profile, including CBC and hemoglobin electrophoresis/HPLC MUST accompany the sample and requisition or be faxed separately to MGL when ordering testing for any of the hemoglobin disorders.

Testing is only available to residents of Canada, except in very specific circumstances where testing is urgent or emergent.  Payment is not required when requests are made for individuals who are insured by Health Insurance BC (administered through the BC Medical Services Plan (MSP)) AND eligible for testing according to the test utilization guidelines / policy. If the individual undergoing testing is not insured by these providers or does not meet utilization guidelines or policy, please complete a billing form; testing will only commence after receipt of billing informationTest prices can be found here.

Molecular genetic testing is limited by the current understanding of the genome and the genetics of a particular disease, as well as by the method of detection used.

Rare single nucleotide variants or polymorphisms could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

A previous bone marrow transplant from an allogenic donor will result in molecular data that reflects the donor genotype rather than the recipient (patient) genotype. Consult the on-service Molecular Geneticist for approach to testing in such individuals.

Transfusions performed with packed red blood cells will generally not affect the outcome of molecular genetic testing. However, if there is no clinical urgency, the cautious approach is to wait one week post packed red cell transfusion before collecting a sample for genetic testing. Consult the on-service Molecular Geneticist as needed.

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.

Autosomal recessive non-syndromic hearing loss/deafness (DFNB1) is characterized by congenital, non-progressive, mild-to-profound sensorineural hearing impairment. No other associated medical findings are present. DFNA3 is a rare form of autosomal dominant non-syndromic hearing loss that is characterized by childhood-onset, progressive, moderate-to-severe high-frequency sensorineural hearing impairment.

The genetic underpinnings of hearing loss are diverse and complicated. Fifty percent (50%) of pre-lingual deafness in children is thought to be genetic. Of this, 70% is non-syndromic (i.e. auditory dysfunction is the only abnormality) and may be autosomal-recessive (75 – 85%), autosomal dominant (15 – 24%), or X-linked (1 – 2%).

Of autosomal recessive non-syndromic hearing loss, DFNB1 is the cause in half. The vast majority of patients with DFNB1 (98%) have 2 identifiable mutations in the GJB2 gene. An additional 2% have one mutation in the GJB2 and a large deletion that includes a portion of the GJB6 gene.

DFNA3 as a cause of autosomal dominant non-syndromic hearing loss is extremely rare. To date, 11 mutations in either GJB2 or GJB6 have been reported to segregate in individuals with DFNA3.

1. Confirmation of diagnosis:
   1. In patients with non-syndromic deafness and a family history suggestive of either autosomal recessive (DFNB1) or autosomal dominant (DFNA3) inheritance
2. Carrier testing:
   1. In adults at risk to be carriers of a GJB2 or GJB6 mutation due to a family history of confirmed GJB2/6-related deafness.
3. Prenatal testing (technically feasible but not routinely performed – contact MGL to discuss):
   1. Pregnancies at risk of non-syndromic deafness due to (a) known mutation(s) in GJB2/GJB6.

Bidirectional Sanger sequencing of the entire coding region and flanking intronic sequences, as well as the exon 1 / intron 1 splice site of the GJB2 gene. If the patient is found to be heterozygous for a GJB2 mutation, gap-PCR is performed to assess for presence of the ΔGJB6-D13S1830 deletion mutation.

GJB2: NM_004004.5 The ‘A’ within the initiation codon, ATG, is designated as nucleotide number 1.

GJB6: NM_006783.4 The ‘A’ within the initiation codon, ATG, is designated as nucleotide number 1.

Blood: 4 mL EDTA is optimal (Minimum: 1 mL EDTA)
DNA: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth and ship to the address below. Samples should be shipped at room temperature with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays). 

Testing is only available to residents of Canada, except in very specific circumstances where testing is urgent or emergent.  Payment is not required when requests are made for individuals who are insured by Health Insurance BC (administered through the BC Medical Services Plan (MSP)) AND eligible for testing according to the test utilization guidelines / policy. If the individual undergoing testing is not insured by these providers or does not meet utilization guidelines or policy, please complete a billing form; testing will only commence after receipt of billing informationTest prices can be found here.

Molecular genetic testing is limited by the current understanding of the genome and the genetics of a particular disease, as well as by the method of detection used. This method will not detect all mutations (e.g., large genomic deletions/duplications, promoter mutations, regulatory element mutations).

For carrier/predictive testing due to a family history, it is generally important to first document the gene mutation in an affected or carrier family member. This information should be provided to the laboratory for assessment of whether the assay is appropriate for detection of the familial mutation, and to aid in the interpretation of data.

In some cases, DNA alterations of undetermined or unclear clinical significance may be identified.

Rare single nucleotide variants or polymorphisms could lead to false-negative results. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

A previous bone marrow transplant from an allogenic donor will result in molecular data that reflects the donor genotype rather than the recipient (patient) genotype. Consult the on-service Molecular Geneticist for approach to testing in such individuals.

Transfusions performed with packed red blood cells will generally not affect the outcome of molecular genetic testing. However, if there is no clinical urgency, the cautious approach is to wait one week post packed red cell transfusion before collecting a sample for genetic testing. Consult the on-service Molecular Geneticist as needed.

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.

Transient Neonatal Diabetes Mellitus; Russell-Silver Syndrome; Silver-Russell Syndrome; Prader-Willi Syndrome; Angelman Syndrome

Uniparental disomy 6 (UPD6): Approximately 40% of 6q-linked transient neonatal diabetes mellitus (TNDM) is associated with paternal UPD6.

Uniparental disomy 7 (UPD7): Approximately 7-10% of individuals with Russell-Silver syndrome have maternal UPD7.

Uniparental disomy 14 (UPD14): Uniparental disomy of chromosome 14 is rare although phenotypes have been described for both maternal and paternal UPD14. Maternal UPD14 is associated with premature birth; growth retardation; short stature; developmental delay; and precocious puberty. Paternal UPD14 is associated with polyhydramnios; omphalocoele; characteristic facial features; a small, bell-shaped chest with short ribs; and developmental delay.

Uniparental disomy 15 (UPD15): Maternal and paternal UPD15 result in different phenotypes: maternal UPD15 gives rise to approximately 25-30% of cases of Prader-Willi syndrome while paternal UPD15 is the cause of 3-5% of cases of Angelman syndrome.

UPD typically arises from the rescue of a trisomic or monosomic zygote resulting in a conception with both copies of a chromosome from a single parent, rather than one copy from each parent. Parents of children with UPD usually have normal karyotypes; however, carrying a structurally abnormal chromosome (such as in the case of certain translocations) may increase the risk of UPD in offspring.

Please see Additional Requirements (below), for information about what samples are required to perform this analysis.

1. Confirmation of diagnosis:
   1. UPD6: infants with transient neonatal diabetes mellitus
   2. UPD7: individuals with features consistent with Russell-Silver syndrome
   3. UPD14: individuals with features suggestive of the clinical phenotype of either maternal or paternal UPD14
   4. UPD15: following positive methylation analysis for either Prader-Willi syndrome or Angelman syndrome, and negative deletion analysis (fluorescent in situ hybridization performed in a Cytogenetics laboratory), UPD testing may be requested to determine if this could be the underlying genetic mechanism for the abnormal methylation pattern. See PWS and AS test algorithms for further details.
2. Prenatal testing (prenatal diagnosis requests are not normally accepted from physicians other than Medical Geneticists):
   1. Pregnancies at increased risk of a clinically-signficant UPD, where cytogenetic analysis has confirmed a normal karyotype. Examples include:
      1. Pregnancies where one of the parents carries a Robertsonian translocation involving chromosome(s) 14 or 15.
      2. Pregnancies where confined placental mosaicism for chromosome 7, 14, or 15 has been identified.
      3. Pregnancies where one of the parents carries a balanced reciprocal translocation AND a certified Cytogeneticist has recommended UPD testing for chromosomes 6, 7, 14, or 15.

This assay assesses the inheritance of polymorphic microsatellite markers located across the appropriate chromosome (6, 7, 14 or 15); at least two microsatellite markers must be informative for interpretation. For assessment of UPD7 and 15, this test is performed using the ABI Linkage mapping set ABI HD5 v.2.5.

Pregnancy-related/Prenatal

If pregnancy management will be altered, 3 weeks; otherwise, routine TAT.

Blood: 4 mL EDTA is optimal (Minimum: 1 mL EDTA)
DNA: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth and ship to the address below. Samples should be shipped at room temperature with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays).  

Prenatal Specimens
Prenatal testing REQUIRES LABORATORY CONSULTATION PRIOR TO THE PROCEDURE and can only be ordered by a Medical Geneticist. Contact the laboratory at 604-875-2852 and choose the appropriate option for the Molecular Geneticist on service.
Chorionic Villi: 20 mg.
Direct Amniotic fluid: 25 mL collected in two separate tubes of equal volume.
Cultured Amniocytes: Two (2) 100% confluent T-25 flasks.
DNA extracted from prenatal specimens: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth. Ship samples by overnight courier with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays) as follows:

• Villi – on wet ice or in media at room temperature
• Amniocytes, Amniotic fluid, DNA – at room temperature

Samples from both biological parents as well as the patient/fetus are required to perform these analyses. If only one parent is available, please consult the on-service Molecular Geneticist.

Testing is only available to residents of Canada, except in very specific circumstances where testing is urgent or emergent.  Payment is not required when requests are made for individuals who are insured by Health Insurance BC (administered through the BC Medical Services Plan (MSP)) AND eligible for testing according to the test utilization guidelines / policy. If the individual undergoing testing is not insured by these providers or does not meet utilization guidelines or policy, please complete a billing form; testing will only commence after receipt of billing informationTest prices can be found here.

Molecular genetic testing is limited by the current understanding of the genome and the genetics of a particular disease, as well as by the method of detection used.

Rare single nucleotide variants or polymorphisms could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

A previous bone marrow transplant from an allogenic donor will result in molecular data that reflects the donor genotype rather than the recipient (patient) genotype. Consult the on-service Molecular Geneticist for approach to testing in such individuals.

Transfusions performed with packed red blood cells will generally not affect the outcome of molecular genetic testing. However, if there is no clinical urgency, the cautious approach is to wait one week post packed red cell transfusion before collecting a sample for genetic testing. Consult the on-service Molecular Geneticist as needed.

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.

Fragile X syndrome; Premature Ovarian Insufficiency; Fragile X Associated Tremor/Ataxia Syndrome; Martin Bell syndrome

FMR1-related disorders include fragile X syndrome, fragile X-associated tremor/ataxia syndrome (FXTAS), and FMR1-related premature ovarian insufficiency (POI). Fragile X syndrome is characterized by moderate intellectual disability in males and mild intellectual disability in affected females.  Males may also display a characteristic appearance, macroorchidism after puberty and behavioral abnormalities.  FXTAS may occur in males and, rarely, in females who have an FMR1 premutation, and is characterized by late-onset, progressive cerebellar ataxia and intention tremor.  FMR1-related POI occurs in approximately 20% of females who have an FRM1 premutation.

The FMR1-related disorders are caused by mutations in the FMR1 gene on the X-chromosome, the most common mutation being expansion of the CGG repeat in the 5′ untranslated region of exon 1. Repeat alleles in the FMR1 gene are classified in our lab as:

• Normal: ~5 to ~54 repeats
• Premutation: ~55 to ~200 repeats and unmethylated
• Full mutation: >200 repeats and methylated

More than 99% of individuals with fragile X syndrome have a loss-of-function mutation in the FMR1 gene caused by the expansion of CGG trinucleotide repeats into the full mutation range, which results in aberrant methylation of the FMR1 gene.

Other mutations in FMR1 that cause fragile X syndrome include deletions and point mutations that disrupt RNA splicing, and missense mutations. All individuals with FXTAS or FMR1-related POI have an FMR1 premutation.

1. Confirmation of diagnosis:
   1. Fragile X Syndrome: Individuals of either sex with global developmental delay (GDD) or intellectual disability (ID) of unknown etiology , or autism spectrum disorders (ASD).  Testing females with learning disabilites may also be considered.
   2. FXTAS: Patients over 50 years of age who have progressive cerebellar ataxia and intention tremor in whom other common causes of ataxia have been excluded.
   3. Premature Ovarian Insufficiency: Women with unexplained premature ovarian insufficiency or reproductive or fertility problems associated with an elevated follicle stimulating hormone (FSH) level in the postmenopausal range before the age of 40.
2. Carrier testing. 

   NB: Carriers have the potential for health problems (FXTAS or FMR1-related POI) in addition to the ability to transmit disease to offspring, therefore this testing in an asymptomatic individual is presymptomatic testing.

   1. Adults with a family history of fragile X syndrome, fragile X tremor/ataxia syndrome, or premature ovarian failure (in more than one family member) if the pedigree structure is consistent with X-linked inheritance and the individual is at risk of inheriting the mutated gene. Referral to a medical geneticist for counselling and assessment should be considered in these cases. 
   2. Adults who have at least one male relative with autism or mental retardation/developmental delay of an unknown etiology within a three-generation pedigree, if the pedigree structure is consistent with X-linked inheritance and the individual is at risk of inheriting the mutated gene. 
3. Prenatal testing (prenatal diagnosis requests are not normally accepted from physicians other than Medical Geneticists):
   1. Pregnancies of females known to have an FMR1 mutation.

Population-based carrier screening (i.e., screening in the absence of any other indication) is not covered by Health Insurance BC (BC MSP). Please contact MGL to discuss.

PCR amplification is performed across the CGG repeat region of the FMR1 gene to determine the repeat size.  In some cases, triplet-primed (tp) PCR (Amplidex PCR/CE FMR1 Reagents, Asuragen, Inc) is performed to assess for the presence of expanded alleles. This assay does not assess methylation status; however, in most cases the repeat is sized well into the full mutation range and, thus, hypermethylation can be assumed.  In rare cases, a repeat collection and testing by Southern blot analysis will be recommended.

 For more information, see FAQ

 Please note: MGL reports repeat sizes only when relevant for risk estimate counselling (i.e. premutation range from 55 – ~120 repeats); otherwise, repeats are categorized as normal, premutation, and full mutation only.

Pregnancy-related/Prenatal

If pregnancy management will be altered, 3 weeks; otherwise, routine TAT.

Blood: 4 mL EDTA is optimal (Minimum: 1 mL EDTA)
DNA: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth and ship to the address below. Samples should be shipped at room temperature with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays).  

Prenatal Specimens
Prenatal testing REQUIRES LABORATORY CONSULTATION PRIOR TO THE PROCEDURE and can only be ordered by a Medical Geneticist. Contact the laboratory at 604-875-2852 and choose the appropriate option for the Molecular Geneticist on service.
Chorionic Villi: 20 mg.
Direct Amniotic fluid: 25 mL collected in two separate tubes of equal volume.
Cultured Amniocytes: Two (2) 100% confluent T-25 flasks.
DNA extracted from prenatal specimens: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth. Ship samples by overnight courier with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays) as follows:

• Villi – on wet ice or in media at room temperature
• Amniocytes, Amniotic fluid, DNA – at room temperature

Testing is only available to residents of Canada, except in very specific circumstances where testing is urgent or emergent.  Payment is not required when requests are made for individuals who are insured by Health Insurance BC (administered through the BC Medical Services Plan (MSP)) AND eligible for testing according to the test utilization guidelines / policy. If the individual undergoing testing is not insured by these providers or does not meet utilization guidelines or policy, please complete a billing form; testing will only commence after receipt of billing informationTest prices can be found here.

Molecular genetic testing is limited by the current understanding of the genome and the genetics of a particular disease, as well as by the method of detection used.  This method will not detect all mutations (e.g., point mutations in the coding region of the gene, large genomic deletions, promoter mutations, regulatory element mutations). 

For carrier/predictive testing due to family history, it is generally important to first document the gene mutation in an affected or carrier family member.  Ideally, this information should be provided to the laboratory for assessment of whether the assay is appropriate for detection of the familial mutation, and to aid in the interpretation of data.

In certain scenarios of repeat size mosaicism, false negative results may occur.  If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

Rare single nucleotide variants or polymorphisms could lead to false-negative results. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

A previous bone marrow transplant from an allogenic donor will result in molecular data that reflects the donor genotype rather than the recipient (patient) genotype.  Consult the on-service Molecular Geneticist for approach to testing in such individuals. 

Transfusions performed with packed red blood cells will generally not affect the outcome of molecular genetic testing.  However, if there is no clinical urgency, the cautious approach is to wait one week post-packed red cell transfusion before collecting a sample for genetic testing.  Consult the on-service Molecular Geneticist as needed.

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.

Prader-Labhart-Willi Syndrome

Prader-Willi syndrome (PWS) is characterized by severe hypotonia and feeding difficulties in early infancy, followed later by excessive eating which, if uncontrolled, leads to the gradual development of morbid obesity. Developmental delay and cognitive impairment occur in all affected individuals. A distinctive behavioral phenotype is often seen as the individual matures. Hypogonadism is present in both males and females.

PWS is caused by abnormal imprinting in the Prader-Willi critical region (15q11.2-q13) that results in the loss of paternal expression of critical genes in the region. This loss of paternal expression can occur by one of several different known genetic mechanisms: paternal deletion in the region; maternal uniparental disomy (UPD) for chromosome 15; or abnormal imprinting. In all cases, an abnormal methylation pattern will be observed in the 15q11.2-q13 region.

1. Confirmation of diagnosis: This test should be used as the first line diagnostic test in a child with a suspected clinical diagnosis of PWS as it provides information regarding methylation, regardless of underlying mechanism. See test algorithm for further details.
2. Prenatal testing (prenatal diagnosis requests are not normally accepted from physicians other than Medical Geneticists):
   1. In pregnancies at risk of PWS.

Pregnancy-related/Prenatal

If pregnancy management will be altered, 3 weeks; otherwise, routine TAT.

Blood: 4 mL EDTA is optimal (Minimum: 1 mL EDTA)
DNA: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth and ship to the address below. Samples should be shipped at room temperature with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays).  

Prenatal Specimens
Prenatal testing REQUIRES LABORATORY CONSULTATION PRIOR TO THE PROCEDURE and can only be ordered by a Medical Geneticist. Contact the laboratory at 604-875-2852 and choose the appropriate option for the Molecular Geneticist on service.
Chorionic Villi: 20 mg.
Direct Amniotic fluid: 25 mL collected in two separate tubes of equal volume.
Cultured Amniocytes: Two (2) 100% confluent T-25 flasks.
DNA extracted from prenatal specimens: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth. Ship samples by overnight courier with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays) as follows:

• Villi – on wet ice or in media at room temperature
• Amniocytes, Amniotic fluid, DNA – at room temperature

Testing is only available to residents of Canada, except in very specific circumstances where testing is urgent or emergent.  Payment is not required when requests are made for individuals who are insured by Health Insurance BC (administered through the BC Medical Services Plan (MSP)) AND eligible for testing according to the test utilization guidelines / policy. If the individual undergoing testing is not insured by these providers or does not meet utilization guidelines or policy, please complete a billing form; testing will only commence after receipt of billing informationTest prices can be found here.

Molecular genetic testing is limited by the current understanding of the genome and the genetics of a particular disease, as well as by the method of detection used.

Rare single nucleotide variants or polymorphisms could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

A previous bone marrow transplant from an allogenic donor will result in molecular data that reflects the donor genotype rather than the recipient (patient) genotype. Consult the on-service Molecular Geneticist for approach to testing in such individuals.

Transfusions performed with packed red blood cells will generally not affect the outcome of molecular genetic testing. However, if there is no clinical urgency, the cautious approach is to wait one week post packed red cell transfusion before collecting a sample for genetic testing. Consult the on-service Molecular Geneticist as needed.

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.

Familial Mediterranean Fever; Recurrent Polyserositis; Familial Paroxysmal Polyserositis; Familial Periodic Fever; TNF receptor-associated periodic syndrome; TRAPS; Familial Hibernian Fever; Autosomal dominant periodic fever syndrome; Hyper-IgD syndrome; Mevalonate Kinase Deficiency; Periodic Fever, Dutch Type; Hypergammaglobulinemia D and periodic fever syndrome

The periodic fever syndromes are disorders of the innate immune system characterized by recurrent episodes of inflammation and fever. The periodic fever syndromes may be inherited or acquired; the hereditary syndromes include familial Mediterranean fever (FMF), TNF receptor-associated periodic syndrome (TRAPS) and hyperimmunoglobulin D syndrome (HIDS), among others.

Familial Mediterranean Fever (FMF) in its classic form (Type 1) is characterized by recurrent episodes of inflammation and serositis including fever, peritonitis, synovitis, pleuritis, and, rarely, pericarditis and meningitis. Amyloidosis, which can lead to renal failure, is the most severe complication. Amyloidosis is the first clinical manifestation in Type 2 FMF. The disorder predominantly affects individuals of Mediterranean descent, particularly North African Jews.

TNF receptor-associated periodic syndrome (TRAPS) is most frequently characterized by recurrent fevers (seen in 95% of cases); arthralgia/myalgia and abdominal pain are also common symptoms. Approximately 15% of individuals with TRAPS eventually go on to develop amyloidosis. The conditions typically presents in early childhood, although this, like the clinical symptoms, is highly variable, both within and between families.

Hyperimmunoglobulin D Syndrome (HIDS) is characterized by recurrent episodes of fever, gastrointestinal symptoms and lymphadenopathy. Individuals often have a high serum immunoglobulin D (IgD) and immunoglobulin A (IgA), and these remain elevated even in the absence of symptoms. The disorder mainly affects individuals with ancestry that can be traced to Northwestern Europe, although it has been reported in other ethnic groups.

FMF is an autosomal recessive disorder caused by mutations in the MEFV gene. MEFV is expressed exclusively in granulocytes and encodes pyrin, a protein critical in regulating the immune response.

TRAPS is an autosomal dominant condition caused by mutations in the TNFRSF1A gene, a member of the TNF-receptor superfamily. Most mutations are found in exons 2 to 4, and around 50% are substitutions of highly conserved cysteines in the extracellular domain. The exact mechanism by which mutations in TNFRSF1A cause TRAPS remains unclear, but most theories suggest that mutations lead to excess TNFR1 signalling. The majority of mutations are highly penetrant, but two recurrent variants (p.Pro46Leu and p.Arg92Gln) that can be seen in patients with milder symptoms of TRAPS can also be seen in healthy individuals.

HIDS is an autosomal recessive disease caused by mutations in the MVK gene. MVK encodes mevalonate kinase, an enzyme in the cholesterol, farnasyl and isoprenoid biosynthesis pathway. Most mutations in MVK that cause HIDS are missense variants that cause a reduction of MVK activity; however, more severe mutations that cause a near complete reduction in MVK activity cause the much more severe condition, mevalonic aciduria.

NOTE: TRAPS and HIDS may only be ordered or must be recommended* by a rheumatologist. 

        *consult letter must be provided

1. Confirmation of diagnosis:

       a.  In individuals with clinical features suggestive of FMF, TRAPS and/or HIDS.

2. Carrier testing

       a.  FMF and HIDS: Adults at risk to be carriers of either FMF or HIDS due to a family history confirmed with molecular testing.

3. Prenatal testing (technically feasible but not routinely performed – contact MGL to discuss):

       a.  Pregnancies known to be at risk of FMF, TRAPS or HIDS due to a family history. The mutation(s) segregating in the family must be known.

4. Presymptomatic testing:

       a.  Individuals at risk to have FMF, TRAPS or HIDS due to a family history of the condition. The mutation(s) segregating in the family must be known. Genetic counseling is recommended prior to presymptomatic testing.

Bi-directional Sanger sequencing across coding regions and flanking intronic sequences of the MEFV, TNFRSF1A and MVK genes.

In cases where FMF, TRAPS, and/or HIDS are requested for the same patient and priority of testing is not indicated, testing will proceed sequentially, starting with FMF. If FMF testing is negative, testing for TRAPS will be performed, followed by testing for HIDS.

MEFV: NM_000243.2

TNFRSF1A: NM_001065.2

MVK: NM_000431.2

The ‘A’ within the initiation codon, ATG, is designated as nucleotide number 1.

Blood: 4 mL EDTA is optimal (Minimum: 1 mL EDTA)
DNA: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth and ship to the address below. Samples should be shipped at room temperature with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays). 

Testing is only available to residents of Canada, except in very specific circumstances where testing is urgent or emergent.  Payment is not required when requests are made for individuals who are insured by Health Insurance BC (administered through the BC Medical Services Plan (MSP)) AND eligible for testing according to the test utilization guidelines / policy. If the individual undergoing testing is not insured by these providers or does not meet utilization guidelines or policy, please complete a billing form; testing will only commence after receipt of billing informationTest prices can be found here.

Molecular genetic testing is limited by the current understanding of the genome and the genetics of a particular disease, as well as by the method of detection used. This method will not detect all mutations (e.g., large genomic deletions/duplications, promoter mutations, regulatory element mutations).

For carrier/predictive testing due to a family history, it is generally important to first document the gene mutation in an affected or carrier family member. This information should be provided to the laboratory for assessment of whether the assay is appropriate for detection of the familial mutation, and to aid in the interpretation of data.

In some cases, DNA alterations of undetermined or unclear clinical significance may be identified.

Rare single nucleotide variants or polymorphisms could lead to false-negative results. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

A previous bone marrow transplant from an allogenic donor will result in molecular data that reflects the donor genotype rather than the recipient (patient) genotype. Consult the on-service Molecular Geneticist for approach to testing in such individuals.

Transfusions performed with packed red blood cells will generally not affect the outcome of molecular genetic testing. However, if there is no clinical urgency, the cautious approach is to wait one week post packed red cell transfusion before collecting a sample for genetic testing. Consult the on-service Molecular Geneticist as needed.

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.

Oculopharyngeal muscular dystrophy (OPMD) typically manifests after age 45 with ptosis and dysphagia.  Weakness often spreads to the tongue, facial muscles, and proximal extremities.  More severe cases (5% – 10%) have earlier onset and more pronounced involvement of the extremities.  There is usually a history of the disorder in one or more family members.

OPMD is caused by an expansion of the GCN trinucleotide repeat in exon 1 of the PABPN1 gene.  Normal repeat length is 10.  Expansions of 12 or more repeats are by themselves sufficient to cause disease and, therefore, account for the autosomal dominant inheritance observed in most families.  Autosomal recessive inheritance is observed in transmission of 11-repeat alleles (i.e. homozygotes are affected and heterozygotes are not).

1. Confirmation of diagnosis:
   1. In individuals with clinical features suggestive of OPMD.
2. Carrier testing:
   1. Individuals at risk to be carriers of the autosomal recessive allele (GCN)11 because of a family history of an individual confirmed to have autosomal recessive OMPD or to be a compound heterozygote for (GCN)12-17/(GCN)11.
3. Prenatal testing (technically feasible but not routinely performed – contact MGL to discuss):
   1. Pregnancies of couples at risk of having a child with OPMD due to known mutation(s).
4. Presymptomatic testing:
   1. Adults known to be at risk of developing OPMD because of a molecularly confirmed family history. Predictive testing will only be performed following genetic counselling by a recognized genetic service.

Sizing of the GCN repeat in the PABPN1 gene is carried out on an ABI genetic analyzer following fluorescence-based PCR amplification.

Blood: 4 mL EDTA is optimal (Minimum: 1 mL EDTA)
DNA: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth and ship to the address below. Samples should be shipped at room temperature with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays). 

Testing is only available to residents of Canada, except in very specific circumstances where testing is urgent or emergent.  Payment is not required when requests are made for individuals who are insured by Health Insurance BC (administered through the BC Medical Services Plan (MSP)) AND eligible for testing according to the test utilization guidelines / policy. If the individual undergoing testing is not insured by these providers or does not meet utilization guidelines or policy, please complete a billing form; testing will only commence after receipt of billing informationTest prices can be found here.

Molecular genetic testing is limited by the current understanding of the genome and the genetics of a particular disease, as well as by the method of detection used. This method will not detect all mutations (e.g., point mutations in the coding region of the gene, large genomic deletions, promoter mutations, regulatory element mutations). For some trinucleotide repeat disorders, repeat expansions have been described that cannot be amplified by PCR. Consideration should be given to this particularly in cases with severe clinical features or early onset; consult the on-service Molecular Geneticist to discuss specific repeat disorders.

For carrier/predictive testing due to family history, it is generally important to first document the gene mutation in an affected or carrier family member. This information should be provided to the laboratory for assessment of whether the assay is appropriate for detection of the familial mutation, and to aid in the interpretation of data.

In some cases, DNA alterations of undetermined or unclear clinical significance may be identified.

In certain scenarios of repeat size mosaicism, false negative results may occur. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

Rare single nucleotide variants or polymorphisms could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

A previous bone marrow transplant from an allogenic donor will result in molecular data that reflects the donor genotype rather than the recipient (patient) genotype. Consult the on-service Molecular Geneticist for approach to testing in such individuals.

Transfusions performed with packed red blood cells will generally not affect the outcome of molecular genetic testing. However, if there is no clinical urgency, the cautious approach is to wait one week post packed red cell transfusion before collecting a sample for genetic testing. Consult the on-service Molecular Geneticist as needed.

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.

Proximal Myotonic Myopathy (PROMM); Ricker Syndrome; DM2

Myotonic Dystrophy Type 2 (DM2) is characterized by myotonia and muscle dysfunction (weakness, pain and stiffness), and may include other multi-system involvement including cataracts and type 2 diabetes.  Onset of symptoms usually occurs between the second to seventh decade, most typically in the third or fourth decade. See PMID: 20301639 for an overview.

DM2 is an autosomal dominant disorder caused by expansion of a CCTG repeat in intron 1 of the CNBP gene.  The CCTG repeat is part of a complex repeat motif consisting of (TG)_n(TCTG)_n(CCTG)_n.

CNBP alleles are typically classified based on total size of the repeat motif, which roughly translates to:

• Normal alleles: up to ~54 CCTG repeats, including mutable normal alleles (27 – ~54 CCTG repeats)
• Full Penetrance: ~55 to over 11,000 CCTG repeats, with a mean of 5000 repeats.

There is no known correlation between the size of the expansion and the severity of the symptoms.

CCTG repeat alleles in the mutable normal range are rare and, as such, their clinical significance is not well characterized.

1. Confirmation of diagnosis:
   1. In individuals with clinical features suggestive of myotonic dystrophy.
2. Presymptomatic testing:
   1. In adults known to be at risk of myotonic dystrophy type 2 because of a molecularly confirmed family history of the condition.

Standard PCR amplification is performed across the (TG)_n(TCTG)_n(CCTG)_n repeat tract of the CNBP gene.  Repeat-primed PCR amplification is performed to assess for the presence of expanded allele(s) not amplifiable by standard PCR.  Repeat size, beyond normal or expanded, is not reported.

Blood: 4 mL EDTA is optimal (Minimum: 1 mL EDTA)
DNA: 100 μL at 200 ng/μL is optimal (Minimum: 30 μL at 200 ng/μL)

Label each sample with three patient identifiers; preferably patient name, PHN, and date of birth and ship to the address below. Samples should be shipped at room temperature with a completed MGL Requisition to arrive Monday to Friday (not on Canadian statutory holidays).  

Shipping Address

Testing is only available to residents of Canada, except in very specific circumstances where testing is urgent or emergent.  Payment is not required when requests are made for individuals who are insured by Health Insurance BC (administered through the BC Medical Services Plan (MSP)) AND eligible for testing according to the test utilization guidelines / policy. If the individual undergoing testing is not insured by these providers or does not meet utilization guidelines or policy, please complete a billing form; testing will only commence after receipt of billing informationTest prices can be found here.

For carrier/predictive testing due to family history, it is generally important to first document the gene mutation in an affected or carrier family member.  Ideally, this information should be provided to the laboratory for assessment of whether the assay is appropriate for detection of the familial mutation, and to aid in the interpretation of data.

In certain scenarios of repeat size mosaicism, false negative results may occur.  If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

Rare single nucleotide variants or polymorphisms could lead to false-negative results. If results obtained do not match the clinical findings, consult the on-service Molecular Geneticist.

A previous bone marrow transplant from an allogenic donor will result in molecular data that reflects the donor genotype rather than the recipient (patient) genotype.  Consult the on-service Molecular Geneticist for approach to testing in such individuals. 

Transfusions performed with packed red blood cells will generally not affect the outcome of molecular genetic testing.  However, if there is no clinical urgency, the cautious approach is to wait one week post-packed red cell transfusion before collecting a sample for genetic testing.  Consult the on-service Molecular Geneticist as needed.

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.