Pathologic Features of Anti-Ku Myositis
Munenori Oyama, Marie‐Therese Holzer, Yuko Ohnuki, Yoshihiko Saito, Yukako Nishimori, Shingo Suzuki, Takashi Shiina, Sarah Léonard-Louis, Olivier Benvéniste, Udo Schneider, Werner Stenzel, Ichizo Nishino, Shigeaki Suzuki, Akinori Uruha
Abstract
OBJECTIVE: Characteristics of myositis with anti-Ku antibodies are poorly understood. The purpose of this study was to elucidate the pathologic features of myositis associated with anti-Ku antibodies, compared with immune-mediated necrotizing myopathy (IMNM) with anti-signal recognition particle (SRP) and anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies, in muscle biopsy-oriented registration cohorts in Japan and Germany. METHODS: We performed a retrospective pathology review of patients with anti-Ku myositis samples diagnosed in the Japanese and German cohorts. We evaluated histologic features and performed HLA phenotyping. RESULTS: = 0.0036, 0.027, 0.016, and 0.026; OR = 0.27, 0, 0, and 0; 95% CI 0.1-0.7, 0-0.8, 0-0.8, and 0-0.8). However, these HLA associations did not remain significant after statistical correction for multiple testing. DISCUSSION: While anti-Ku myositis shows necrotizing myopathy features, they can be distinguished from anti-SRP/HMGCR IMNM by their MHC class II expression and clusters of perivascular inflammatory cells. The HLA analyses suggest that anti-Ku myositis may have different subsets associated with myopathologic subgroups.