In most cases FSHD is an autosomal dominant disease, meaning that only one copy of the genetic lesion is needed for the disease to show symptoms and there is 50% likelihood that the mutation will be inherited. Most cases of FSHD (FSHD1A) are caused by a partial deletion of a DNA repeat structure at the end of Chromosome 4. This exerts a direct or indirect effect on the functions of many genes, some of which are involved in regulating muscle. In a small number of cases (FSHD1B or FSHD2) the same symptoms have been observed but they are caused by a mutation in the SMCHD1 gene on chromosome 18.
While there is no cure for FSHD great strides are being made in understanding the genetic abnormalities that result in muscle weakness. This new understanding has resulted in the development of animal models for FSHD and exploration of promising approaches for treatment. In addition, there is an increasing interest in trying to establish standards for the management of FSHD. Efforts are currently underway to standardise the outcome measures used to assess the symptoms of FSHD to ensure that their suitability for clinical trials. An agreed dataset for FSHD registries was decided upon in 2011 and a number of patient registries have been established with more in development (more information can be found by following the menu links to the left).
FSHD can be diagnosed through a blood test but it is often recommended that parents are also tested. (Centres testing for FSHD can be found here)