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About Rare DiseasesRare Disease Wiki

Facioscapulohumeral Muscular Dystrophy (FSHD)

Name of disease:

Facioscapulohumeral Muscular Dystrophy (FSHD)

ICD-10 diagnosis code:

G71.02

Causes:

  • FSHD is caused by ectopic expression of the germline transcription factor DUX4 gene in muscle cells.
  • The most common found in 95% of patients is called FSHD Type 1 (FSHD1). FSHD1 is associated with the deletion of a chromosomal tandem repeat called D4Z4 near the end of chromosome 4 at the 4q35 location.
  • The remaining 5% is called FSHD Type 2 (FSHD2) which is linked to the genes SMCHD1 DNMT3B and LIRF1.

Mode of inheritance:

  • FSHD1 is inherited in an autosomal dominant pattern meaning it takes only one mutation (from one parent) to cause the disorder.
  • This altered piece of DNA also can occur spontaneously in a child as he or she develops in the womb which accounts for 10% to 30% of FSHD1 cases.
  • The inheritance of FSHD2 is not fully established and in most cases may require mutations in SMCHD1 on chromosome 19. Approximately 60% of FSHD2 cases appear to be sporadic.

Prevalence:

FSHD has an estimated prevalence of 1:20,000 people in the US.

Diagnosis:

  • Physical exam
  • Review of family and medical history
  • Blood test to measure levels of serum creatine kinase an enzyme that is released into the bloodstream when muscle fibres are deteriorating and serum aldolase an enzyme that helps break down sugars into energy. Elevated levels of either of these enzymes can indicate a problem with muscles and a need for additional testing. However a normal creatine kinase level does not rule out FSHD.
  • Neurological tests to rule out other nervous system disorders identify patterns of muscle weakness and wasting test reflexes and coordination and detect muscle contractures.
  • Muscle biopsies which involve the removal of muscle tissue using a biopsy needle or during a simple surgical procedure. The tissue is then examined under a microscope. In FSHD a muscle biopsy might reveal several abnormalities but none are uniquely characteristic for the disease or the muscle might even appear normal. To confirm a diagnosis of FSHD with certainty a genetic test is needed.
  • Genetic testing to confirm FSHD Type 1 or Type 2.

Age of onset:

FSHD has historically been divided into two clinical subgroups: early-onset FSHD with facial weakness before the age of 5 years and scapulohumeral weakness before the age of 10 years and classic FSHD with a typical onset between 15 and 30 years but often diagnosed throughout the adult lifespan.

Common signs and symptoms:

  • Symptoms of FSHD in children might include:
    • Their eyes being slightly open when sleeping
    • Not being able to squeeze their eyes shut tightly
    • Not being able to purse their lips
  • Older children and adults might have rounded shoulders and thin weak upper arms. This can cause pain in the shoulders and back.
  • In adulthood FSHD usually affects the:
    • Face
    • Shoulders
    • Upper arms
    • Back
    • Calves
    • Pelvis girdle muscles
    • Ankles
  • In over half of those with FSHD there can be weakness at the knees hips and back. This can cause a backward leaning and high stepping style of walking.
  • The condition can develop asymmetrically.

Available treatment (medicinal and non-medicinal):

  • There is no cure for FSHD and no specific drug treatment.
  • Regular exercise and hydrotherapy can help maintain muscle function for as long as possible.
  • Try to eat a healthy balanced diet and maintain a healthy weight. This will help reduce stress on the already weakened muscles.
  • Using orthoses (devices that support the feet) can help people with FSHD. They can improve FSHD symptoms like foot drop and shoulder weakness.
  • A surgical procedure called scapular fixation which fixes the shoulder blades to the ribs at the back can help some people with FSHD to regain some more use of their arms.
  • If the patient’s eyes become dry and inflamed and they cannot close them at night then surgery to bring the eyelids closer could be required. This option would be considered if artificial tears are not helping.
  • Painkillers may be prescribed to help manage the pain of FSHD symptoms.

Disease management tips:

  • Massage or warm moist packs (for example hot packs you can put in a microwave) may be good for discomfort associated with FSHD.
  • Take regular rests and avoid a Boom-Bust cycle of activity.
  • Eat fresh seasonal fruit and vegetables instead of processed foods caffeine and alcohol.

References:

Other useful websites:

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