Limb-girdle dystrophies, like all muscular dystrophies, are progressive disorders. The rate of progression, however, varies widely in different types of limb-girdle muscular dystrophies and between individuals. Autosomal recessive limb-girdle muscular dystrophy of childhood generally progresses more rapidly, leading to loss of ambulation in late childhood or adolescence and death in early adulthood (Ben Hamida et al 1983; Zatz et al 1989; Farag and Teebi 1990; Azibi et al 1991), although milder cases are also seen. Autosomal dominant forms of limb-girdle muscular dystrophy, even those that begin in early childhood, are more benign and life expectancy can be normal (Bethlem and Van Wijngaarden 1976; Arts et al 1978; Mohire et al 1988; Tachi et al 1989; Jobsis et al 1999).
Physical disability in limb-girdle muscular dystrophy is dependent on the distribution and severity of muscle weakness. Not surprisingly, loss of walking ability occurs earlier when the disease begins in the pelvic girdle. The interval between onset of symptoms and inability to walk is highly variable. Muscle contractures may contribute to severe disability in later stages. Respiratory muscle impairment can occur, with muscles of forced expiration involved earlier than those of inspiration. Pulmonary function tests typically disclose a decreased vital capacity, inspiratory reserve volume, and maximum breathing capacity. Because the disease process is slow in most cases, compensatory changes occur and a normal resting minute volume is generally maintained for long periods of time. Ventilation perfusion mismatch does not occur in limb-girdle muscular dystrophy, probably because of the uniformly diffuse disease process. Respiratory components affected include diaphragmatic and intercostal muscles. Pneumonia and respiratory failure can eventually shorten the life span. Some patients with mild phenotypes, however, remain mobile and have a normal life span.
Pathological changes in the myocardium in limb-girdle muscular dystrophy are seen in some forms more than others (Stubgen 1993) and are generally similar to, but less severe than, in Duchenne dystrophy. Clinically overt cardiac involvement, however, is rare in limb-girdle muscular dystrophy except in a few subtypes.