[Inclusion body myositis. Report of 4 cases].

Inclusion body myositis (IBM) is a primary inflammatory myopathy characterized by an older age at presentation. We describe four IBM cases fulfilling Mendell's diagnostic criteria. All patients were older than 60 years at diagnosis and the mean length of time from onset to diagnosis was 5.7 years. Two of them complained of leg weakness with unsteady gait and the other two, of upper limb weakness. Three patients had dysphagia, one of them had diaphragmatic paralysis and another had bilateral blepharoptosis. Histological sections of the muscle biopsy showed mononuclear cell invasion of nonnecrotic muscle fibers, rimmed vacuoles, intracellular amyloid deposits and 16-21 nm tubulofilaments by electron microscopy. Mitochondrial anomalies were found in two cases. Only one patient had transient response to steroid therapy. Our serie shows that clinical presentation of inclusion body myositis includes a broader spectrum than the classical description.