Familial reducing body myopathy.

Reducing body myopathy (RBM) is a rare pathologically defined myopathy characterized by the presence of inclusion bodies which are abnormally stained by menadione-nitroblue-tetrazolium. The clinical symptoms vary widely as to the age of onset, disease progression and severity. Among the many reported patients, there have been only three families with this disorder, showing a manifold of clinicopathological features in each family. We report a fourth family with RBM affecting a boy and his mother. The proband (boy) began to have difficulty putting on his trousers at age 10years and difficulty arising from a chair at 11years. His spine was rigid. His mother, on the other hand, noticed foot-drop at the age 29, but the clinical course was rapidly progressive, and she was wheelchair-bound at 34years. Both patients had generalized muscle weakness and atrophy and with mild CK elevation. Muscle pathology was characterized by the presence of atrophic fibers with reducing bodies in some areas. As these patients demonstrate, clinical symptoms in RBM are very variable, even within the same family. There are no specific clinical characteristics distinctive to RBM, thus further studies are necessary to characterize this disorder both clinically and pathologically.