FSHD global research foundation

The Genetics of FSHD
The genetic cause of FSHD was first identified over 15 years ago. It was found that 95 per cent of people affected by FSHD have a decreased number of D4Z4 repeats on chromosome 4q35. While the discovery of this chromosomal defect in FSHD was a huge success for FSHD research, unfortunately the gene(s) causing the disease has still not been identified. Once scientists can identify the gene(s) responsible for producing FSHD much valuable information and therapies will be unlocked.

Unlike other forms of dystrophy the D4Z4 deletion found in FSHD does not appear to affect genes that are known to be critical for skeletal muscle function or structure. Individuals appear to require the existence of 11 or fewer repeat units to be at risk for FSHD. International researchers have found that when the entire region where the FSHD deletion occurs is removed, there are birth defects, but no specific defects on skeletal muscle. This has forced scientists to question the possibility of FSHD having a position effect. There is much FSHD research to be done to understand these findings.

FSHD is a very difficult disease to understand and research has been hampered due to lack of funding for FSHD research and thus a lack of interest from researchers. The FSHD Global Research Foundation’s major aim is to rectify this problem.

Preimplantation Genetic Diagnosis (PGD) for FSHD
PGD has been used to successfully identify embryos carrying specific genetic disorders to avoid the reoccurrence of a disease in further generations. Most diseases have identifiable gene changes (mutations) that are identified in the PGD testing process to determine which embryos contain these changes and which do not contain the change.

FSHD is different in that it does not have an identifiable gene mutation. Instead FSHD appears to be a result of a change at the end of chromosome 4 which then affects some unknown gene further down the chromosome.

People with FSHD have a 50 per cent chance of passing it on to any children. PGD can be used to reduce this risk substantially. Sydney IVF use polymorphic DNA markers down near the end of the chromosome to identify which chromosome ends are likely to be present in any embryo. By avoiding embryos carrying the associated markers, the likelihood of FSHD transmission is significantly reduced.

Is testing 100% accurate?
No, but it gives better than a 9 in 10 chance of avoiding passing the gene on to the next generation. Couples can have greater confidence in initiating a pregnancy that is unlikely to result in a child affected by this disease.

There is now a DNA genetic test performed by looking at the patient’s blood and detecting deletion of the 4q35 Chromosome. It is considered 98% reliable for many cases where diagnosis of FSHD is uncertain or impossible.