Characterized by a benign limb girdle myopathy
with mild-to-moderate weakness and wasting of muscles. Onset is in early
infancy or childhood (age 2-5 years) with a benign course and slow
progression, leaving some of the affected patients only minimally impaired
in old age. However, many patients require a wheelchair after 50 years of age,
and some die of respiratory failure as a consequence of progressive
respiratory muscle weakness, particularly of the diaphragm. Proximal and
extensor muscles are more affected than distal and flexor muscles. Early
flexion contractures involve the elbows, ankles, interphalangeal joints of
the last four fingers, and planta pedis. Congenital torticollis may be
present. Cardiac and respiratory involvement usually is not a feature of
this condition.