TY - JOUR T1 - Iliopsoas Muscle Involvement due to Granulomatosis with Polyangiitis JF - The Journal of Rheumatology JO - J Rheumatol SP - 1582 LP - 1583 DO - 10.3899/jrheum.191310 VL - 47 IS - 10 AU - Yoshinori Taniguchi AU - Hirofumi Nishikawa Y1 - 2020/10/01 UR - http://www.jrheum.org/content/47/10/1582.abstract N2 - Swollen iliopsoas muscle has a broad differential diagnosis, including infection, neoplasm, hemorrhage, sarcoidosis, and vasculitis including granulomatosis with polyangiitis (GPA)1.A previously healthy 42-year-old man presented to our clinic with 4 weeks of fever, malaise, left orbital puffiness, and low back pain. Laboratory tests showed normal renal and hepatic function and C-reactive protein (CRP) level of 7.45 mg/dL. Blood cultures were negative. There had been no response to antibiotics. Magnetic resonance imaging and computed tomography (CT) revealed retro-orbital mass (Figure 1A … ER -