Necrotising myositis in Behçet's disease: characteristic features on magnetic resonance imaging and a review of the literature.

CASE REPORT A 29 year old man was first admitted to Matsunami General Hospital because of high fever and muscle pain of both lower legs, finally resulting in him being unable to walk. Painful multiple subcutaneous nodules of both lower legs and the left arm were seen. There was no history of trauma. Total leucocytes, erythrocyte sedimentation rate, and C reactive protein were raised. The serum creatine kinase value was normal. An MRI study of the lower legs (fig 1) showed a focal mass-like lesion, about 3 cm in diameter, in the left gastrocnemius muscle with a decreased intensity on a T1 weighted image compared with that for normal muscle. Gadolinium enhanced T1 weighted images showed a well defined rim of contrast enhancement and a hypointense central area. An axial T2 weighted image showed bright signal intensity in and around the focal mass-like lesion. The same MRI findings were seen in the other nodules of the lower legs. Computed tomography (CT) did not disclose the focal mass-like lesion. Antibiotics were not effective. The symptoms and multiple nodules resolved spontaneously about one month after admission, and the patient was discharged. One month after discharge, he was admitted to our hospital because of a relapse, with similar symptoms. Painful multiple subcutaneous nodules of both lower legs, in different areas from those of his previous admission, were found. MRI findings of the mass lesions were similar to those of the previous admission. On admission the patient had polyarthritis and skin lesions. Recurrent aphthous ulcerations had been noted over the previous two years. Pathergy testing was positive. A skin biopsy was performed and showed thrombophlebitis. HLA-B51 was positive. From these results, Behçet’s disease was diagnosed. A biopsy of a nodule from the left gastrocnemius muscle was carried out. Examination of the muscle biopsy specimen obtained from the nodular lesion showed an inflammatory granulation predominantly with an infiltration of neutrophils and macrophages, associated with focal central necrosis of the muscle and perivasculitis in the surrounding muscular tissue. A culture of the tissue specimen was negative for bacteria. These findings were consistent with necrotising myositis. The symptoms and multiple nodules of the legs resolved spontaneously. After discharge, colchicine was given, and no painful multiple subcutaneous nodules have reappeared.