Case report 866. Pseudotumor of the muscle associated with necrotizing vasculitis of medium- and small-sized arteries and chronic myositis.

Abstract

A case of polymyositis and localized vasculitis presenting as a muscular pseudotumor of a lower extremity and periostitis several years after the onset of symptoms was reported and the MRI characteristics were described. This imaging modality demonstrated muscle signal abnormalities in several muscle groups and was useful in ruling out the presence of a mass and fatty degeneration of the muscle. The ability of the STIR sequence (Fig. 3D) to show muscle abnormalities and to allow fatty infiltration or degeneration to be ruled out has not been reported before in patients with vasculitic muscle involvement.