Facioscapulohumeral muscular dystrophy (Landouzy-Dejerine Disease; FSHD)
Incidence
It has autosomal dominant inheritance. New mutation may account for 10 to 20 percent of cases. Prevalence estimates are similarly influenced by clinical variability, but a level around 5 per 100,000 has been found in several populations.
Clinical Characteristics
Facioscapulohumeral disease is a variable and relatively benign muscular dystrophy showing autosomal dominant inheritance. New mutation may account for 10 to 20 percent of cases. Prevalence estimates are similarly influenced by clinical variability, but a level around 5 per 100,000 has been found in several populations, with no striking geographical variation so far noted. The gene has been located on the distal long arm of chromosome 4. Facioscapulohumeral dystrophy, while often benign, may also be seriously disabling in some patients. It is a dominantly inherited disorder that is, like myotonic dystrophy, exceptionally variable. Although traditionally regarded as a benign condition, systematic family and population studies have shown that about 20 percent of patients are severely disabled by age 40. Conversely, some individuals remain minimally affected throughout life. As the name of the disorder implies, facial weakness is prominent, along with involvement of the shoulder girdle and proximal arm muscles. Initially the patient has trouble blowing or puckering the lips. As the muscle weakness becomes more severe, a masklike facial expression develops and the child can not close the eyes while sleeping. Pelvic-girdle involvement is also seen but generally appears later and is less marked than the involvement of the shoulder girdle, in contrast to the situation in Duchenne, Becker, and other limb-girdle dystrophies, where the lower girdle is affected earlier and more severely. Lower-limb involvement in FSHD is frequently characterized by distal weakness of the peroneal muscles, resulting in footdrop, and a characteristic gait in more severe cases results from the combination of footdrop and pelvic girdle weakness. The onset of FSHD is frequently in childhood; facial weakness may be seen in family photographs even when the diagnosis has only been made much later. Scapular "winging" is another early sign, but a mild degree may be seen in normal, lax-jointed children. Smooth and cardiac muscle are notably unaffected, as is mental function. Some evidence of wider systemic involvement comes from the finding of associated neural hearing loss. Both muscle biopsy and electromyography frequently show changes suggestive of a neurogenic basis, along with myopathic changes. These are sometimes so marked as to cause confusion with the group of spinal muscular atrophies. Most cases have normal CPK.
Precipitants
no
Provocation Tests
no
Diagnostic Procedures
Clinical diagnosis.