Miositis con cuerpos de inclusión (forma esporádica)

Sporadic inclusion body myositis (IBM) is a major subgroup among idiopathic inflammatory myopathies. The clinical and pathologic findings of this disease are well defined but are not always easy to identify. IBM mainly affects men aged more than 50 years old who usually present with chronic and sometimes asymmetrical weakness and atrophy, thus requiring a wide differential diagnosis. Some well-characterized autoimmune diseases are associated with IBM. However, unlike dermatomyositis, there is no association with neoplastic disease. Clinical and histopathological data are mandatory in the diagnosis of IBM, while laboratory and electromyographic studies are usually non-diagnostic. In contrast, magnetic resonance imaging may help in diagnosis and should possibly be included in the diagnostic criteria. The pathogenesis of IBM is still not well-defined, as it involves interrelations among inflammatory, degenerative and mitochondrial phenomena. Diagnostic delay is the rule, and the response to available treatments is poor except when an autoimmune disease is associated with IBM.