Key words Behçet disease, children, MRI, muscle biopsy, myositis.Behçet disease (BD) is a systemic disorder of recurrent acute inflammation, characterized by major symptoms of oral aphthous ulcers, uveitis, skin lesions, and genital ulcers. The diagnosis is made using the criteria established by the International Study Group for Behçet disease in 1990. 1 In Japan, the diagnosis was also made according to the Japanese criteria revised in 2003. 2 But the clinical course of BD is highly variable, with recurrent exacerbations and disease-free intervals of uncertain duration. BD is rare in children and the clinical feature of childhood BD is thought to differ from that in adults. 3 Myositis is rarely associated with BD and may confuse clinicians, especially if a definite diagnosis of BD is not made. In this article, we report on a case with recurrent myositis as the main manifestation of BD, and we illustrate the importance of this condition.
Case reportThe patient is a 16-year-old Japanese girl with a history of bronchial asthma. She first presented with swelling and pain in the left calf at the age of 9 years. Ten days later, her right calf was also affected, resulting in her being unable to walk, and she was admitted to our hospital. On physical examination, her bilateral calves were tender, warm, slightly reddish, and swollen. In blood examinations, C-reactive protein (CRP) had mildly elevated to 0.97 mg/dL, erythrocyte sedimentation rate (ESR) to 30 mm/hr, and aldolase to 7.8 (normal 2.7-5.9) IU/l. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatine phosphokinase (CPK) were normal. Both anti-nuclear antibody (ANA) and rheumatoid factor (RF) were negative, and other autoimmune screening tests were also unremarkable. Magnetic resonance imaging (MRI) of the bilateral calves revealed increased signal intensity on fat-suppressed T2-weighted images over bilateral gastrocnemius and soleus muscles, more prominent in the left side (Fig. 1). These areas were isointense with the normal muscle on T1-weighted images. She was diagnosed as having myositis based on these findings, but the cause of it could not be determined. The symptoms resolved spontaneously within 1 month and she was discharged from our hospital.Seven months later, at the age of 10 years, she had a recurrence of left calf myositis. Aphthous ulcerations and genital ulcers, which developed with surrounding erythema, were seen for the first time. At that time, a muscle biopsy was performed. Histopathological examination of left gastrocnemius muscle specimens showed perivascular infiltrates of inflammatory cells, suggesting perivasculitis (Fig. 2a). Myocytes were normal, but we might have missed the most affected lesion in this procedure. The symptoms recovered fully after 3 weeks without medical treatment.Five months after the second discharge, she had swelling and tenderness in her bilateral calves again. Three weeks after the onset of this episode, oral prednisone (2 mg/kg/day) was given for 2 weeks and was tapered over the next 3 we...