common disorders of muscle
Muscle disease can be acquired or genetically mediated. Acquired muscle diseases such as inflammatory myopathies are most often proximal and symmetrical in distribution. A notable exception is inclusion body myositis, which has a predilection for the quadriceps and finger flexors and may be quite asymmetrical. Genetic myopathies or muscular dystrophies may also demonstrate specific patterns of muscle group involvement that may aid in diagnosis. In general, the degree of clinical weakness in a particular muscle correlates well with the severity of the findings on needle EMG examination.