[A case of rigid spine syndrome--histological findings of muscles].

A 10-year-old boy with rigid spine syndrome was reported. He had mild weakness in the limb, and moderate weakness in the neck flexor and extensor muscles since early childhood. Because of limited flexion of the spine, he could not bend down. CT of the muscles revealed increased low density in the erector spine muscle, predominantly at the lumbar level. In the biopsy specimens obtained from the left biceps brachii and erector spine muscles, there was a variation in fiber size with scattered necrotic and regenerating fibers, and fibrosis, predominantly in the latter. Except for scattered fibers with rimmed vacuoles, the overall histopathological features were similar to those seen in progressive muscular dystrophies, suggesting that the dystrophic process is one of the major pathomechanisms for rigid spine syndrome.