Facioscapulohumeral Muscular Dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant dystrophy from inappropriate expression of DUX4.

• Prevalence 1 in 8,000 to 20,000.

• FSHD1 (95%): D4Z4 macrosatellite contraction on chromosome 4q35 (1 to 10 units) on a permissive haplotype. FSHD2: SMCHD1 mutations.

• Onset in teens to 30s; asymmetric progression; 20% need a wheelchair.

• Extramuscular: retinal telangiectasia (Coats disease), high frequency hearing loss.

• Facial weakness (inability to whistle, incomplete eye closure, transverse smile), scapular winging, humeral muscle wasting ("Popeye arms"), foot drop, abdominal weakness (Beevor sign), lumbar lordosis.

• Asymmetric involvement, back pain, fatigue.

• Infantile severe form with Coats disease and hearing loss.

• Genetic testing: D4Z4 repeat size (pulse field gel electrophoresis, Southern blot, molecular combing) and permissive haplotype; SMCHD1 sequencing.

• CK normal to 5 times normal.

• Muscle MRI: asymmetry, fat replacement, STIR hyperintensity.

• Retinal examination, audiometry; ECG (cardiac involvement unusual); respiratory function if severe.

• No disease modifying therapy proven.

• Physiotherapy, aerobic exercise, scapular fixation surgery (scapulothoracic arthrodesis) for selected patients, ankle foot orthoses.

• Pain: paracetamol, NSAIDs, amitriptyline.

• Respiratory monitoring, non invasive ventilation if needed.

• Retinal laser or cryotherapy for telangiectasia, hearing aids.

• Genetic counselling, prenatal diagnosis.