Facioscapulohumeral muscular dystrophy

FSHD is a disease characterised by death of muscle cells and tissue leading to progressive muscle weakness. The name FSHD refers to the muscles typically affected:

• face (facio)
• shoulders (scapula)
• upper arm (humeral)

The condition can appear at any time from infancy until a person is in their 50s, but is most commonly diagnosed in teenagers and young adults.

The condition usually progresses slowly, often with long periods of stability. Eventually, however, the loss of muscle strength can be extremely debilitating, resulting in difficulty walking, talking, smiling and eating.

Although most people with FSHD have a normal life expectancy, they can experience chronic pain, fatigue, loss of independence and social isolation due to their condition.

The symptoms of FSHD are due to muscle weakness and may include:

• inability to smile, whistle, close eyes completely (weak facial muscles)
• difficulty throwing a ball, shoulder blades that “wing” out (weak shoulder blades)
• loss of upper arm strength
• protuberant abdomen, excessive curve in lower back (weak abdomal muscles)
• weak leg muscles
• foot drop (foot muscle weakness)
• muscle pain
• fatigue

The symptoms range in severity: some people are relatively unaffected by the condition, while others eventually require a wheelchair.

FSHD that presents during infancy is usually more severe than adult-onset FSHD and may also include hearing and vision loss. Men with FSHD tend to show an earlier onset of disease and worse symptoms than women.

FSHD is an inherited disease, meaning it is caused by a change in DNA (genetic mutation) transmitted from parents to their children. Parents with the mutation have a 50 per cent chance of passing the condition on to each child.

There are two subtypes of FSHD caused by different genetic mutations:

• FSHD1 is due to a reduced number of copies of a DNA segment on chromosome 4. This is the most common type of FSHD.
• FSHD2 is caused by mutation in SMCHD1, a gene discovered by WEHI researchers.

Both mutations lead to production of a protein that is toxic to muscle cells, leading to progressive muscle weakening.

There is currently no specific treatment or cure for FSHD. Approaches to manage the disease and alleviate symptoms include:

• physiotherapy
• exercise
• diet
• pain medication
• speech therapy
• surgery

Scientists at WEHI are working towards developing targeted drugs for FSHD. Their work focuses on the gene SMCHD1, which is faulty in people with FSHD2. SMCHD1 is an epigenetic regulator that normally switches off expression of a protein that destroys muscle. Restoring SMCHD1 activity could potentially switch off the toxic protein and protect muscle function.

Our researchers are currently screening thousands of drug-like molecules in search of chemicals that boost SMCHD1 activity. Promising molecules will then be refined to develop drugs to treat FSHD or even prevent the disease in people carrying FSHD mutations.

WEHI researchers are not able to provide specific medical advice to individuals. For further information, please visit the FSHD Global Research Foundation, Muscular Dystrophy Australia or consult your medical specialist.