Genetic Testing

Your doctor will need to requisition the tests at these labs. For a complete list, visit:

• Online International Directory of Genetic Testing Laboratories – search for FSHD and click on the “Test” tab.
• NCBI Genetic Testing Registry – Click on “Test” link

These labs do not offer direct patient consultation.

1) University of Iowa Diagnostic Laboratories

Client Services Phone: (866) 844-2522

Mary Sue Otis, UI Diagnostic Laboratories Manager Email: marysue-otis@uiowa.edu Phone: (319) 356-3339 Fax: (319) 384-7213

Steven A. Moore MD PhD Professor of Pathology Email: steven-moore@uiowa.edu Phone: 319-335-8215

Testing offered: FSHD1 4q35 deletion detection by PFGE and Southern blot analysis & 4qA/4qB allele determination; FSHD2 SMCHD1 sequencing; methylation testing (for FSHD1 and FSHD2). Details and requisition forms to order testing are available at these links:

• Detection of Abnormal Alleles with Interpretation (FSHD1 and FSHD2)

Additional Testing Offered: Prenatal diagnosis and 4qA/4qB allele testing. Prenatal specimens should be cultured to 100% confluency in 6 T-25 flasks and must not be frozen.

Overseas clients can send specimens to UIDL via FedEx overnight using this International MD Requisition Form.  The lab requires payment prior to testing. Credit cards accepted.

2) Children’s Hospital of Eastern Ontario Molecular Genetics Diagnostic Laboratory Ottawa, Ontario, Canada Director: Nancy Carson, PhD, FCCMG Email: carson@cheo.on.ca Phone: (613) 737-7600, Ext. 3282 Fax: (613) 738-4822

3) University of Leiden, the Netherlands Testing for FSHD1 and FSHD2 can be ordered through Leiden University in the Netherlands. It takes about eight weeks for results to be reported. Download the University of Leiden genetic test request form (pdf).

If you have tested negative for FSHD1 See the information provided below.

The genetic test for FSHD1 consists of measuring the size of the DNA segment containing multiple repeats of identical DNA sequences called D4Z4. Molecular scissors (restriction enzymes called EcoRI and Blnl) are used to cut the DNA on either side of the repeats, and the fragments from chromosome 4 are sized. In healthy individuals, both copies of chromosome 4 will have more than 10 repeats of D4Z4, whereas in individuals with FSHD, one copy of chromosome 4 will have only between one and 9 repeats. This shortened, or “contracted”, chromosome must be combined with a “permissive” 4qA polyadenylation site in order for the person to have FSHD.

The genetic test report gives two numbers, one from each copy of chromosome 4, corresponding to the size of the D4Z4 region, measured in “kilobases.” If the D4Z4 region is more than 50 kilobases (>13 repeats), this is in the healthy range. Between 39 and 50 kilobases (10-13 repeats) is considered “borderline.” Less than or equal to 38 kilobases (1-9 repeats) is considered to be FSHD1. (Reference: University of Rochester Medical Center.)

The genetic test for FSHD2 consists of measuring the methylation levels in the D4Z4 region on chromosome 4. Recently, researchers found mutations in a gene called SMCHD1 in approximately 80 percent of patients with FSHD2. Over 52 mutations in SMCHD1 have been found in FSHD2 patients.

You should ask to be tested for FSHD2. The test is available through the University of Iowa. If you are negative for both FSHD1 and FSHD2, you may wish to be screened for limb-girdle muscular dystrophies through Invitae’s limb-girdle genetic testing program. If that too does not lead to a genetic diagnosis, you might consider enrolling in the Boston Children’s Hospital study of molecular analysis of patients with neuromuscular disease or the Broad Institute’s Rare Genomes Project. 

A member of the FSHD Society made an inquiry as to what the following genetic test results report meant in terms of translating fragment sizes measured in kilobases (kb) of DNA to the numbers of repeats left (e.g. these are my test results and how does this translate into number of repeats?).

To make sense of the test results: Each one of the inquirer’s chromosome 4’s is being tested for FSHD. First they are cut with an enzyme called EcoRI and then further checked to see if it is an unusual arrangement of DNA with another enzyme which further cuts the DNA called BlnI.

The results show the inquirer’s unaffected chromosome 4 and affected chromosome 4. The unaffected chromosome (or allele 1) is the first when cut with enzymatic scissors. The length of this segment is greater than 40 and, therefore, according to the calculations below, the number of repeats is greater than the number of repeats needed to be affected, or positive, for FSHD.

The second number shows the affected chromosome (e.g., allele 2) is 18 kb in length when cut with only one scissors. It is checked for special cases and to see if there are 10q repeats within the shortened fragment. It is 3 kb less due to the test and is not a special case. The repeats are all from chromosome 4. D4Z4 repeat numbers were calculated from EcoRI-fragment sizes as follows: number of repeats = (fragment size in kb – 5 kb flanking sequence)/3.3 kb.

This would appear to be (18 – 5 )/3.3 = 3 or 4 repeats. Allele 2 is the disease-causing allele, as it contains a deletion within the FSHD diagnostic range.