Sporadic inclusion body myositis and hereditary inclusion body myopathy.

Sporadic inclusion body myositis (s-IBM) is a common but under-recognized myopathy in individuals over 50 years of age. An awareness of the clinical phenotype and of the electrodiagnostic and histopathologic features should lead to improved recognition, and should minimize confusion with polymyositis, motor neuron disease, and other neuromuscular disorders. Treatment efficacy has been difficult to judge because of the insidious progression of the disease over many years, but immunomodulating therapy is generally less effective than in polymyositis and dermatomyositis, and may not be effective at all in many patients. The hereditary inclusion body myopathies (h-IBM) are a heterogeneous group of recessively and dominantly inherited vacuolar myopathies that share some histologic features with s-IBM. Oxidative stress may play a role in the pathogenesis of both s-IBM and h-IBM.