Rimmed vacuolar distal myopathy: a clinical, electrophysiological, histopathological and computed tomographic study of seven cases

The following report describes the clinical, laboratory, electrophysiological, histopathological and computed tomographic studies of seven cases of distal myopathy with rimmed vacuoles in the muscle fibers. Each displayed several characteristic features. First, the onset was in early adulthood. Second, there was a unique distribution of muscle involvement: tibialis anterior and extensor digitorum and hallucis muscles were initially and most severely affected. The hamstrings and adductors of the thigh were also markedly involved. The gluteus medius and minimus muscles and the neck flexors were mildly affected in the relatively early stages. In contrast, the gastrocnemius, soleus, quadriceps femoris, and gluteus maximus muscles were well preserved until an advanced stage. Third, serum creatine kinase activity was normal or only mildly elevated; fourth, EMG were mainly myopathic, with certain neuropathic features; and fifth, histopathologically rimmed vacuoles in muscle fibers were found associated with certain “neuropathic” features, such as angular fibers, clustering of atrophic fibers, pyknotic nuclear clumps, and fiber-type predominance. The characteristic distribution of skeletal muscle involvement was particularly noticeable, together with certain “neuropathic” features of the EMG and muscle biopsy in rimmed vacuolar distal myopathy.