This is polymyositis. Note the marked inflammatory cell infiltrate. This is an autoimmune disease that can be associated with polymyositis or dermatomyositis. Polymyositis results from the cytotoxic effects of CD8+ lymphocytes recognizing HLA class 1 MHC molecules on sarcolemmal membranes. Dermatomyositis is mainly mediated via a vasculitis affecting small capillaries, and has a skin rash (typically the violaceous "heliotrope" rash of eyelids). |
![]() ![]() ![]() |