Inclusion Body Myositis

Inclusion body myositis is an insidious, slowly progressive myopathy of middle-aged and older individuals. Because of these characteristics, diagnosis is often delayed. Affected muscle is marked by the presence of rimmed vacuoles, inclusions, and an inflammatory infiltrate largely made up of CD8 T lymphocytes and macrophages. The inclusions contain beta-amyloid and phosphorylated tau protein, as well as other components. Theories of the pathogenesis of this disorder of older individuals include those based on evidence of the unfolded protein response leading to endoplasmic reticulum stress, abnormalities of proteosomal degradative function, mitochondrial dysfunction, the immune response, and amyloid toxicity. There is no proven, reliably effective medication for this disorder.