facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is a form of muscular dystrophy characterized by extremely variable degrees of facial, scapular and lower limb muscle involvement.

Epidemiology

It is considered one of the more common hereditary muscular disorders with a prevalence of ~1 in 8,000.

Clinical presentation

Initially there may be a restricted pattern of weakness with early involvement of the facial and scapular stabilizer muscles and with a descending course resulting in later involvement of either the distal anterior leg or hip-girdle muscles.

Pathology

Genetics

It carries an autosomal dominant inheritance.

Two types have been described:

  • type I (95%): associated with a decreased number of D4Z4 repeats on chromosome 4q35
  • type II (5%): no associated deletions

Radiographic features

MRI

MRI is considered sensitive and may show a specific pattern of muscle fatty replacement and atrophy, particularly in upper girdle muscles.

The most frequently affected muscles are trapezius, teres major and serratus anterior. Asymmetric muscle involvement maybe significantly higher in FSHD as compared to non-FSHD.

Whole body MRI may be useful to assess the pattern of muscle involvement.

Treatment and prognosis

Its severity and disease course can vary considerably.

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