[A patient of late-onset nemaline myopathy with mononuclear cell infiltration]

We described a 50-year-old woman with late-onset nemaline myopathy with focal mononuclear cell infiltrates in her muscle biopsy. She developed difficulty in climbing stairs, and elevating her arms for 5 months after the onset of the disease. On admission, neurological examination revealed moderate weakness and atrophy in the proximal limb and neck muscles. Laboratory studies were within normal limits except mildly elevated serum CK and aldolase levels. Electromyography showed myopathic changes in the right triceps and quadriceps muscles examined. A biopsy from the left biceps brachii muscle revealed increased variation in fiber size, with numerous basophilic atrophic fibers. There were some foci of mild mononuclear cell infiltration. Most of basophilic fibers contained nemaline bodies on modified trichrome stain. On electron microscopy numerous nemaline bodies were present in fibers with marked myofibrillar degeneration. Azathioprine and prednisolone administration was not effective to improve her condition. As mononuclear cell infiltration has been occasionally described in the previously reported patients of adult-onset nemaline myopathy, inflammatory process may have some roles in formation of nemaline bodies on the way of acute myofibrillar degeneration.