Peter Špalek
Inclusion body myositis is the most common but under-recognized acquired muscle disease after the age of 50 years. Awareness of the clinical phenotype and of the electromyographic and histopathologic features should lead to improved recognition, and should minimize confusion with polymyositis and other neuromuscular disorders. Most patients present with weakness and atrophy of the quadriceps muscles, weakness and atrophy of the forearm muscles, especially the flexor digitorum profundus and flexor policis longus. The etiology and pathogenesis of sporadic inclusion body myositis are still poorly understood. However, genetic factors, ageing, environmental triggers and inflammatory (autoimmune) mechanisms might all play a role. Unlike polymyositis and dermatomyositis, sporadic inclusion body myositis causes slowly progressing muscular weakness and atrophy and is unresponsive to conventional forms of immunotherapy. This review covers the histopathology, pathogenesis, clinical presentation, diagnosis and treatment of sporadic inclusion body myositis.