Focal Myositis of the Leg Presenting as Fever of Unknown Origin Detected by FDG PET/CT.

Focal myositis is an uncommon inflammatory pseudotumor of the skeletal muscle that may mimic neoplastic and inflammatory diseases. We present one case of focal myositis involving the left proximal vastus lateralis and vastus intermedius, and left soleus showing intense FDG uptake on FDG PET/CT. This case indicates that focal myositis should be considered as a differential diagnosis in patients with focal hypermetabolic muscular lesions, including benign and malignant tumors, necrotizing autoimmune myopathy, nodular fasciitis, myositis ossificans, and muscular sarcoidosis.