A 15-year-old girl presented with pain in the back of both thighs. On examination there was severe pain but no erythema or palpable tumor in her thighs. Findings from laboratory examinations were normal except for the serum creatine kinase levels, the concentrations of which increased from 3977 U/L to 5877 U/L (to convert to microkatal per liter, multiply by 0.0167) over the course of 3 days of clinical follow-up. Magnetic resonance imaging of her thighs revealed an increased signal intensity on the T2-weighted image. The abnormal signal was more clearly revealed on the short tau inversion recovery image (Figure 1). Microscopic examination of the biopsied muscle tissue showed myopathic changes with degeneration, necrosis, and myophagia (Figure 2). Findings from immunological investigation for viral infections in her serum samples showed high titers of complement fixation antibody for influenza A virus. Considering the progressive worsening of symptoms and the rapid increase of the creatine kinase levels, this patient was treated with 1000 mg of methylprednisolone sodium succinate intravenously each day for 3 days; this resulted in the resolution of symptoms and normalization of the creatine kinase levels. Magnetic resonance images at 30-day follow-up (Figure 1) showed a normal intensity at the bilateral biceps femoris muscle. Her serum creatine kinase level was 48 U/L. The patient remained symptom free during a 6-month follow-up. Figure 1. View LargeDownload Magnetic resonance images through the lower part of the thighs. A, Transverse T2-weighted image shows hyperintensity of the bilateral biceps femoris muscle. Anterior and adductor groups are normal. B, Transverse T2-weighted short tau inversion recovery sequence shows the lesions. C, Intensity became normal at the corresponding region in magnetic resonance images at 30-day follow-up. The high-intensity spot is a site where muscle biopsy has been performed (arrow). Figure 2. View LargeDownload Biopsy of the lesion in the left biceps femoris muscle. Muscle biopsy specimen stained with hematoxylin-eosin shows necrotic fibers with phagocytosis (arrows) and ghostlike appearance (arrowheads). Some muscle fibers are regenerating (original magnification ×100). Lundberg1 published the first report of benign acute childhood myositis under the term “myalgia cruris epidemica.” The disease includes clinical features of acute myositis predominantly affecting the gastrocnemius and soleus muscles in school-aged children; it also has an epidemiological or etiological association with viral infections.2 The mechanism of myositis restricted to muscles that include the calves, soles, or thighs remains unknown. A possible mechanism might be a unique antigen(s) expressed in these muscles, which would be the target for an autoimmune-mediated response followed by viral infections. Previous pathological investigations showed various features including normal,1 segmental rhabdomyositis,2 myositis,3 or moderate muscle necrosis with interstitial inflammation.4 The term myopathy might be appropriate for some cases, including ours, because of the few features of inflammation. Further pathological and immunological studies could lead to a reconsideration of the disorder's pathologic makeup. Back to top Article Information Correspondence: Dr Kawarai, Department of Neurology, Hyogo Brain and Heart Center, Saisho-Ko 520, Himeji City, Hyogo Prefecture, Japan (firstname.lastname@example.org). Author Contributions:Study concept and design: Kawarai and Nishimura. Acquisition of data: Kawarai and Nishimura. Analysis and interpretation of data: Kawarai, Nishimura, Taniguchi, Saji, Shimizu, Tadano, Shirabe, and Kita. Drafting of the manuscript: Kawarai and Nishimura. Critical revision of the manuscript for important intellectual content: Kawarai, Nishimura, Taniguchi, Saji, Shimizu, Tadano, Shirabe, and Kita. Administrative, technical, and material support: Kawarai and Nishimura. Study supervision: Kawarai,Nishimura, Taniguchi, Saji, Shimizu, Tadano, Shirabe, and Nishimura. Financial Disclosure: None reported. References 1. Lundberg A Myalgia cruris epidemica. Acta Paediatr 1957;46 (1) 18- 31PubMedGoogle ScholarCrossref 2. Mackay MTKornberg AJShield LKDennett X Benign acute childhood myositis: laboratory and clinical features. Neurology 1999;53 (9) 2127- 2131PubMedGoogle ScholarCrossref 3. Mejlszenkier JDSafran APHealy JJEmbree LOuellette EM The myositis of influenza. Arch Neurol 1973;29 (6) 441- 443PubMedGoogle ScholarCrossref 4. Ruff RLSecrist D Viral studies in benign acute childhood myositis. Arch Neurol 1982;39 (5) 261- 263PubMedGoogle ScholarCrossref
Archives of Neurology – American Medical Association
Published: Aug 1, 2007
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