Dystrophia Myotonica 1; Steinert’s Disease

Myotonic dystrophy type 1 (DM1) is a disorder of smooth and skeletal muscle that also affects the eye, heart, endocrine system, and central nervous system. The clinical continuum has been divided into roughly three categories: mild (cataract and myotonia), classic (muscle weakness and wasting, myotonia, cataract and, often, cardiac conduction abnormalities), and congenital (severe hypotonia and severe generalized weakness at birth, often with respiratory insufficiency and, frequently, intellectual disability).

DM1 is caused by an increased number of CTG trinucleotide repeats in the 3′ untranslated region of the DMPK gene. The inheritance pattern is autosomal dominant with anticipation. Anticipation is the phenomenon of increased severity or decreased age of onset in successive generation due to expansion of the unstable repeat. In DM1, anticipation is typically greater with maternal transmission of the expanded allele.

DMPK alleles are classified as:

• Normal: 5 to 34 CTG repeats
• Mutable Normal: 35 to 49 repeats
  These alleles are not disease-causing, but may be at risk of expansion into the pathogenic range in subsequent generations.
• Full Penetrance: >50 repeats

In general, longer CTG repeat expansions correlate with an earlier age of onset and more severe disease; however, there is overlap in the repeat ranges associated with the categories of clinical presentation. Individuals with mild DM1 typically have between 50 and ~150 repeats; those with classic DM1 typically have between ~100 to ~1000; and, those with congenital DM1 typically have >1000 repeats. Most often, a child with congenital DM1 has inherited the expanded DMPK allele from the mother. Although expansion into the disease-causing range typically occurs in maternal transmission, paternal inheritance has been described.

1. Confirmation of diagnosis:
   1. In individuals with clinical features suggestive of myotonic dystrophy.
2. Prenatal testing (prenatal diagnosis requests are not normally accepted from physicians other than Medical Geneticists):
   1. Pregnancies at risk of myotonic dystrophy type 1 because of a history of molecularly confirmed DM1 in one parent.
3. Presymptomatic testing:
   1. Adults known to be at risk of myotonic dystrophy type 1 because of a molecularly confirmed family history of the condition.

PCR and triplet-primed (tp) PCR amplification is performed across the CTG repeat region of the DMPK gene to assess for expansion.  Sizing is performed up to ~100 repeats; sizing beyond 100 repeats is not possible with this assay.    

In rare cases, a repeat collection and testing by Southern blot analysis will be recommended.

For more information, see FAQ

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.

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.

Isolated Craniosynostosis; Non-Syndromic Craniosynostosis; Coronal Craniosynostosis

The phenotype of Muenke syndrome varies considerably. Clinical features may include cranial suture synostosis, ocular hypertelorism, ptosis or proptosis, midface hypoplasia, temporal bossing, high-arched palate, strabismus, hearing loss, developmental delay, intellectual disability; carpal bone and/or tarsal bone fusions brachydactyly, broad toes, broad thumbs, and clinodactyly.

Muenke syndrome is inherited in an autosomal dominant manner, but shows reduced penetrance. All individuals are heterozygous for the FGFR3 mutation c.749C>G (p.Pro250Arg).

1. Confirmation of diagnosis:
   1. In individuals with clinical features suggestive of Muenke syndrome (non-syndromic craniosynostosis).
2. Carrier testing:
   1. Although this is an autosomal dominant condition, carrier testing may be relevant to identify non-penetrant mutation carriers.
3. Prenatal testing (technically feasible but not routinely performed – contact MGL to discuss):
   1. In pregnancies of a couple in which one parent has Muenke syndrome.

Bidirectional Sanger sequencing across the c.749C>G (p.Pro250Arg) FGFR3 mutation.

NM_000142.4 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).  

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.

Hypokalemic periodic paralysis manifests in a paralytic form (reversible, flaccid paralysis characteristically triggered by a carbohydrate-rich meal or post-exercise rest) and a myopathic form (exercise intolerance due to progressive muscle weakness). The myopathy is independent of paralytic symptoms and may be the sole manifestation of the condition.

CACNA1S and SCN4A are the only two genes known to be associated with hypokalemic periodic paralysis (HypoPP).  Inheritance is autosomal dominant and most affected individuals will have an affected parent.  This assay will detect recurrent variants in CACNA1S exons 11 and 30 (including c.1583G>A (p.Arg528His), c.1582C>G (p.Arg528Gly), c.3716G>A (p.Arg1239His), c.3715C>G (p.Arg1239Gly) and c.1466G>A (p.Arg489His)) accounting for approximately 43-67% of cases, and recurrent variants in SCN4A exon 12 (including c.2005C>G (p.Arg669Gly), c.2006G>A (p.Arg669His), c.2014C>A (p.Arg672Ser), c.2015G>A (p.Arg672His), c.2014C>G (p.Arg672Gly), c.2014C>T (p.Arg672Cys)) accounting for an additional 4-15% of cases.  Around one third of individuals with HypoPP will have no variants identified.

1. Confirmation of diagnosis:
   1. In individuals with clinical features suggestive of hypokalemic periodic paralysis.
2. Prenatal testing (technically feasible but not routinely performed – contact MGL to discuss):
   1. Pregnancies known to be at risk of hypokalemic periodic paralysis when the CACNA1S or SCN4A mutation is known.
3. Presymptomatic testing:
   1. Asymptomatic children and adults at risk of this condition because of a family history. The CACNA1S or SCN4A mutation must be known.

Bidirectional Sanger sequencing of CACNA1S exons 11 and 30 and of SCN4A exon 12, and their flanking intronic sequences. These exons encompass the recurrent mutations described for this disorder.

CACNA1S: NM_000069. The ‘A’ within the initiation codon, ATG, is designated as nucleotide number 1.

SCN4A: NM_000334.4. 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., mutations outside the regions tested as described above, 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. 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 rare 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.

Hypochondroplasia is a skeletal dysplasia characterized by short stature; stocky build; disproportionately short arms and legs; broad, short hands and feet; mild joint laxity; and macrocephaly. The skeletal features are very similar to achondroplasia but tend to be milder. Medical complications common to achondroplasia (e.g., spinal stenosis, tibial bowing, obstructive apnea) occur less frequently in hypochondroplasia, but deficits in mental capacity and/or function may be more prevalent. Children usually present as toddlers or school-age children with short stature; limb disproportion and other features become more prominent with time. Individuals with mild achondroplasia and severe hypochondroplasia present similarly.

The majority of cases of hypochondroplasia are due to mutations in the FGFR3 gene. Inheritance is autosomal dominant, although most cases are due to de novo mutations (i.e., both parents are of normal stature). Approximately 70% of probands with hypochondroplasia are heterozygous for the FGFR3 p.Asn540Lys mutation, due to one of two recurrent FGFR3 mutations, c. 1620C>A (in 70%) and c.1620C>G (in 30%). The achondroplasia mutation, p.Glu380Arg (c.1138G>A; c.1138G>C), may present clinically as severe hypochondroplasia . Other rare FGFR3 mutations have been reported.

1. Confirmation of diagnosis:
   1. In individuals with clinical features suggestive of hypochondroplasia.
2. Prenatal testing (technically feasible, but not routinely performed – contact MGL to discuss):
   1. In pregnancies born to a couple in which one or both parents has hypochondroplasia

Bidirectional Sanger sequencing of the regions of FGFR3 encompassing the common hypochondroplasia mutation p.Asn540Lys (c.1620C>A; c.1620C>G), the rare p.Asn540Thr (c.1619A>C), p.Asn540Ser (c.1619A>G), and p.Ile538Val (c.1612A>G) mutations and the achondroplasia mutation p.Glu380Arg (c.1138G>A; c.1138G>C).

NM_000142.4 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).  

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.

Gamstorp Disease; Adynamia Episodica Hereditaria With Myotonia; Adynamia Episodica Hereditaria Without Myotonia; Normokalemic Periodic Paralysis; Sodium Channel Muscle Disease

Hyperkalemic periodic paralysis is characterized by attacks of flaccid limb weakness, which may be accompanied by weakness of the eyes, throat and trunk. During attacks, serum potassium concentration is >5 mmol/L or has increased by at least 1.5 mmol/L over baseline. Muscle strength and serum postassium concentration are normal between attacks. Onset is generally before 20 years of age.

SCN4A is the only gene identified to date that is known to be associated with hyperkalemic periodic paralysis. Four recurrent mutations account for almost all of the SCN4A disease alleles; together these account for approximately 55% of cases.

1. Confirmation of diagnosis:
   1. In individuals with clinical features suggestive of hyperkalemic periodic paralysis.
2. Prenatal testing (technically feasible but not routinely performed – contact MGL to discuss):
   1. Pregnancies known to be at risk of hyperkalemic periodic paralysis and the SCN4A mutation is known.
3. Presymptomatic testing:
   1. Asymptomatic children and adults at risk of this condition because of a family history. The SCN4A mutation must be known.

Bidirectional Sanger sequencing of SCN4A exons 13 and 24 and their flanking intronic sequences, which encompass the four common mutations associated with hyperkalemic periodic paralysis: c.2065C>A (p.Leu689Ile), c.2078T>C (p.Ile693Thr), c.2111C>T (p.Thr704Met) and c.4774A>G (p.Met1592Val).

NM_000334.4 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., mutations outside the regions tested as described above, 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. 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 rare 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.

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.

Huntington Chorea

Huntington disease (HD) is a progressive disorder of motor, cognitive, and psychiatric disturbances; onset is usually between 35 and 45 years of age. Early manifestations can include subtle changes in eye movements, coordination, minor involuntary movements, difficulty in mental planning, and a depressed or irritable mood. These evolve into more prominent chorea, with voluntary activity becoming increasingly difficult, and worsening dysarthria and dysphagia. The late stages are characterized by severe motor disability.

HD is caused exclusively by a trinucleotide (CAG) repeat expansion mutation in the HTT gene. The inheritance pattern is autosomal dominant with anticipation. Anticipation is the phenomenon of increased severity or decreased age of onset in successive generation due to expansion of the unstable repeat. In HD, anticipation is generally greater with paternal transmission of the expanded allele.

Alleles in the HTT gene are classified as:

• Normal: < 26 CAG repeats
• Normal (intermediate): 27 to 35 CAG repeats
• HD-causing with reduced penetrance: 36 to 39 repeats
• HD-causing with full penetrance: > 40 repeats

Normal (intermediate) alleles are not disease causing, but may be at risk of expansion into the pathogenic range in subsequent generations.  Alleles of 36-39 repeats show reduced penetrance; an individual with an allele in this range may or may not develop symptoms of Huntington disease during their lifetime.  Expanded alleles >100 repeats have been reported for infantile/juvenile onset HD.

1. Confirmation of diagnosis:
   1. In individuals with clinical features suggestive of HD.
2. Prenatal testing (prenatal diagnosis requests are not normally accepted from physicians other than Medical Geneticists):
   1. Pregnancies at risk of being affected with HD. Samples from both parents may be required to complete the prenatal diagnosis analysis.
3. Presymptomatic testing:
   1. Adults known to be at risk of developing symptoms due to a molecularly confirmed family history. Predictive testing will only be performed following genetic counselling by a recognized genetic service.

Sizing of the CAG repeat is performed on an ABI genetic analyzer following fluorescence-based PCR amplification. To aid in interpretation, PCR amplification is also performed to size the adjacent non-pathogenic CCG repeat, and the combined CAG/CCG repeat region. As required, triplet-primed (tp) PCR is performed.

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). 

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. 

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.

Please refer to the BC Ministry of Health Guidelines and Gene Reviews for detailed background on the clinical features of HFE-HH.

Please refer to the BC Ministry of Health Guidelines and Gene Reviews for up-to-date information regarding the genetics of HFE-HH.

Genetic testing for HFE-HH is performed in accordance with BC Ministry of Health Guidelines.

There have been logistical changes to the ordering and laboratory algorithms (figures 1 and 2) that are not reflected in these Guidelines; the ordering algorithm (figure 1) has been updated here:

Changes to the approach to ordering

Please see HFE-HH Ordering Algorithm

All testing for HFE-HH should be ordered with the Standard Outpatient Laboratory Requisition (SOPLR), using the appropriate indications box under HFE-Hemochromatosis, as outlined in the algorithm.

The MGL general requisition is no longer used to order this test.

Changes to laboratory algorithm

Collection/Chemistry laboratories should follow their site-specific process for collection and processing, as established in consultation with BC chemistry laboratories and MGL.  This algorithm essentially follows figure 2 from the BC Ministry of Health Guidelines, with minor changes.

The C282Y mutation is detected by PCR-based RFLP analysis; this assay will not detect other rarer HFE alleles, including the H63D variant.

Blood: 0.5 – 4 mL EDTA

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., mutations outside the regions tested as described above, large genomic deletions, promoter mutations, regulatory element mutations).

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.

Familial Recurrent Polyneuropathy; Tomaculous Neuropathy

Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) is characterized by repeated focal pressure neuropathies such as carpal tunnel syndrome and peroneal palsy with foot drop, typically with a family history consistent with autosomal dominant inheritance. Prolonged distal nerve conduction latencies is found on electrophysiologic studies of all individuals, symptomatic or not.

In the majority of cases (80%), HNPP is caused a 1.5 Mb contiguous gene deletion at 17p11.2, which includes the PMP22 gene. In the remaining 20%, the condition is caused by a point mutation in the PMP22 gene. Inheritance is autosomal dominant, although 20% of cases arise due to de novo mutations.

1. Confirmation of diagnosis:
   1. In individuals wtih clinical features suggestive of HNPP.
2. Prenatal diagnosis (technically feasible but not routinely performed – contact MGL to discuss):
   1. Pregnancies to couples in which one person has HNPP
3. Presymptomatic testing:
   1. Adults at risk of inheriting HNPP from a parent and who are not yet symptomatic may be referred for predictive testing for HNPP.
   2. Requests to test asymptomatic children who are at risk of developing HNPP are only accepted following genetic counselling by a recognized genetic service.

Multiplex ligation-dependent probe amplification (MLPA) analysis is carried out with the P033-B2 probe mix (MRC-Holland) to determine the gene dosage (i.e. number of copies) of the PMP22 gene. Note: This assay will detect both CMT1A and HNPP.

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). 

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.