Polymyositis is a rare inflammatory disease of striated muscle and is a sign of malignant tumor in 30% to 50% of patients over 40 years of age. A patient had Kaposi sarcoma occurring in association with polymyositis. To my knowledge, the occurrence of Kaposi sarcoma and polymyositis has not previously been reported.
Dantzig PI. Kaposi Sarcoma and Polymyositis. Arch Dermatol. 1974;110(4):605-607. doi:10.1001/archderm.1974.01630100061016