title: Giant cell polymyositis and myocarditis associated with myasthenia gravis and thymoma.
abstract: We describe an unusual case of myasthenia gravis. Our patient had been diagnosed as having myasthenia gravis with thymoma at the age of 64 years, and died of acute respiratory failure at the age of 80 years. Post mortem examination revealed CD8-positive lymphocytic infiltration with numerous giant cells in the skeletal muscles and myocardium. Immunohistochemical and ultrastructural studies revealed that there were two types of giant cells: histiocytic and myocytic in origin. Furthermore, both types of giant cells were immunopositive for proteins implicated in the late endosome and lysosome-protease systems, suggesting that endocytosis may be the key mechanism in the formation of giant cells. The present case, together with a few similar cases reported previously, may represent a particular subset of polymyositis, that is, giant cell polymyositis and myocarditis associated with myasthenia gravis and thymoma.
authors.affiliation: Department of Neuropathology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan. t-kon@umin.ac.jp
authors.forename: Tomoya
authors.initials: T
authors.lastname: Kon
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Mori
authors.forename: Kunikazu
authors.initials: K
authors.lastname: Tanji
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Miki
authors.forename: Tamaki
authors.initials: T
authors.lastname: Kimura
authors.forename: Koichi
authors.initials: K
authors.lastname: Wakabayashi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D011992:Endosomes / Q000473:pathology; D005260:Female; D015726:Giant Cells / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology; D009157:Myasthenia Gravis / Q000473:pathology*; D009205:Myocarditis / Q000473:pathology*; D009206:Myocardium / Q000473:pathology; D017285:Polymyositis / Q000473:pathology*; D013945:Thymoma / Q000473:pathology*; D013953:Thymus Neoplasms / Q000473:pathology*