case_images: PMC11799667_01
case_images: MRI findings. MRI revealed a high signal on STIR and T1-weighted images in the upper and lower limb muscles bilaterally. MRI findings suggested muscle inflammation. (A) STIR coronal images of the bilateral lower thighs. (B) T1-weighted bilateral horizontal images of the lower thighs. (C) STIR bilateral horizontal image of the lower thighs. MRI: magnetic resonance imaging, STIR: short inversion time inversion recovery.
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case_images: Skeletal muscle magnetic resonance imaging (MRI) revealed high signals on short inversion time inversion recovery (STIR) in the trunk and proximal upper and lower limb muscles (Figure 1).
case_images: Histopathological findings of the muscle biopsy tissue. Hematoxylin and Eosin staining showed increased internal nuclei, numerous necrotic myofibers (arrows), and moderate fiber size variations (A), positive major histocompatibility complex class I (B), and membrane attack complex (C) immunostaining. (D): Type 2C fibers (arrow; fibers of the intermediate color), which reflect immaturity of myofibers, are scattered. This finding suggests the presence of active necrotic and regenerating processes. Adenosine triphosphatase stain at 4.3 pH. Darkly stained fibers are type 1 fibers, while the white ones are type 2A or 2B fibers. (E): Sarcoplasmic p62 aggregates in a fine granular pattern.
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case_images: Histological examination revealed irregular muscle fiber sizes, and scattered necrotic and regenerating fibers, but no perimysial atrophy, intramysial sheath fibrosis, or mononuclear cell infiltration (Figure 2A). Immunohistological staining revealed mild, but diffuse, human leukocyte antigen-ABC expression on myofiber membranes (Figure 2B) and deposition of the membrane invasion complex, the complement C5b-9 complex, on the myofiber membrane in one muscle fiber (Figure 2C). Type 2C fibers were scattered (Figure 2D), and myofibers with diffuse cytoplasmic p62-positive fine aggregates were observed (Figure 2E).
case_images: The clinical course of the 51-year-old male patient after his IMNM diagnosis. Day 0 indicates the date of hospital admission. After admission, steroid pulse therapy, high-dose gamma globulin therapy, and oral tacrolimus were administered. However, his muscle weakness did not improve. The patient experienced persistent muscle weakness and myalgia, which gradually improved after intravenous cyclophosphamide therapy.. IMNM: immune-mediated necrotizing myopathy.
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case_images: F3
case_images: The patient's clinical course is detailed in Figure 3.