PMC5173511_01
Magnetic resonance imaging (MRI) of the lower limbs. a, b: August 2005; c, d, e: June 2006; f, g, h: January 2008. a, b, e, f, h: Axial (a, f) and coronal (b, e, h). a-f: Unenhanced MRI image and g: gadolinium-enhanced MRI image. STIR images show high signal intensity in the affected muscles of the lower legs (white arrowhead). c, d: Axial and coronal STIR images show high signal intensity in the affected femoral muscles (white arrowhead). f, g: Axial gadolinium-enhanced MRI (g) shows no enhanced area in the thickened fascia of the right gastrocnemius, which showed high signal intensity on the unenhanced MRI image (f) (white arrow).
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Atrophic change of the muscle was also noted (Fig. 1a and b). MRI revealed multiple high-intensity areas in the lower limbs that included the femoral muscle (both sides of the vastus lateralis, the left vastus intermedius, the right biceps femoris, and the left gracilis) (Fig. 1c and d) and the right gastrocnemius (Fig. 1e) on STIR images. MRI findings revealed high signal intensity of the bilateral gastrocnemius (Fig. 1f and h), left popliteus muscle, and right semimembranosus on STIR images (data not shown), and mild edema was evident in the subcutaneous tissue in both lower limbs in January 2008. As thickening of the fascia of the right gastrocnemius on the STIR image (Fig. 1f, white arrow) demonstrated no gadolinium contrast enhancement (Fig. 1g, white arrow), it was considered to result from edema. MRI findings in December 2014 revealed no inflammatory change (Fig. 1f).
Muscle biopsy. a, b: Hematoxylin and Eosin staining, 400x; c-f: immunohistochemical staining, 400x; c: CD4; d: CD8; e: CD68; f: CD20; g: electron microscopy. A muscle biopsy of the right gastrocnemius reveals mononuclear inflammatory cells (a, b: black arrowhead) that infiltrated the interstitial spaces of the muscle without vasculitis findings, along with muscle fiber necrosis and regeneration (a, b: white arrowhead). Infiltrating cells predominantly consisted of CD4+T cells, CD68+macrophages, and CD20+B cells accompanied by a few CD8+T cells (c-f: white arrow). Electron microscopy of the muscle biopsy specimens reveals nemaline rods (g: black arrows).
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A muscle biopsy of the right gastrocnemius revealed interstitial muscle infiltration by mononuclear inflammatory cells without findings of vasculitis, along with muscle fiber necrosis and regeneration (Fig. 2a and b). Immunohistochemical staining of the muscle biopsy showed that the infiltrating cells predominantly consisted of CD4+ T cells, CD68+ macrophages, and CD20+ B cells accompanied by a few CD8+ T cells (Fig. 2b-f). Electron microscopy of the muscle biopsy specimens in February 2008 revealed nemaline rods (Fig. 2g, black arrows).
Clinical course of the patient. PSL: prednisolone, MTX: methotrexate, AZA: azathioprine, IVIG: high-dose intravenous immunoglobulin
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The clinical course is shown in Fig. 3.