Clinical and pathologic features of focal myositis

• Published in: Muscle & nerve Vol. 23; no. 10; pp. 1569 - 1575
• Main Authors: Smith, A. Gordon, Urbanits, Sabine, Blaivas, Mila, Grisold, Wolfgang, Russell, James W.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York John Wiley & Sons, Inc 01.10.2000; Wiley
• Subjects: Adolescent; Adult; Biological and medical sciences; dermatomyositis; Diseases of striated muscles. Neuromuscular diseases; Female; focal myositis; Humans; inflammatory myositis; Magnetic Resonance Imaging; Male; Medical sciences; Middle Aged; Muscles - pathology; Muscles - physiopathology; myopathy; Myositis - pathology; Myositis - physiopathology; Neurology; polymyositis; Human; Immunohistochemistry; Pathology; Striated muscle disease; Nervous system diseases; Myositis; Diagnosis; Muscular fiber; Hypertrophy; Inflammatory disease; Myopathy
• ISSN: 0148-639X; 1097-4598
• DOI: 10.1002/1097-4598(200010)23:10<1569::AID-MUS14>3.0.CO;2-M

To clarify the nosology of focal myositis (FM), we report the clinical and pathologic features of eight patients presenting with focal enlargement of one muscle. Most patients improved without immunosuppressive therapy, and none developed polymyositis. Pathologic features were those of an inflammatory myopathy, with muscle fiber hypertrophy and moderate to severe inflammation. In most cases, a clustering of tightly packed muscle fibers, enveloped by a thick bundle of fibrosis, was associated with the diagnosis of FM. Immunohistochemistry showed T cell predominance within the interstitial infiltrates in all cases. No evidence of vasculitis was present. Our findings suggest that FM is a benign condition that has certain clinical features separating it from other inflammatory myopathies. Pathologic changes, such as large clusters of nesting muscle fibers surrounded by thick fibrosis, are more characteristic of FM than polymyositis. © 2000 John Wiley & Sons, Inc. Muscle Nerve 23: 1569–1575, 2000