Fig. 7From: Muscle biopsy features of idiopathic inflammatory myopathies and differential diagnosisDiffuse MHC-I sarcolemmal immunoreactivity in a muscle biopsy of a patient with polymyositis (PM) (upper panels). On the contrary in necrotizing autoimmune myopathy (NAM), MHC-I is expressed only on membrane and/or sarcoplasm of necrotic fibers, by endomysial macrophages besides, as normal finding, in muscle blood vessels (lower panels)Back to article page