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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