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. 2020 Jul 1;77(7):872-877.
doi: 10.1001/jamaneurol.2020.0673.

Association of Dermatomyositis Sine Dermatitis With Anti-Nuclear Matrix Protein 2 Autoantibodies

Michio Inoue  1   2 , Jantima Tanboon  1   2 , Shinya Hirakawa  3 , Hirofumi Komaki  4 , Takeshi Fukushima  5 , Hiroyuki Awano  6 , Takashi Tajima  7 , Kenji Yamazaki  8 , Ryutaro Hayashi  9 , Tatsuo Mori  10 , Kazumoto Shibuya  11 , Takahiko Yamanoi  12 , Hajime Yoshimura  13 , Tomohiro Ogawa  14 , Atsushi Katayama  15 , Fuminobu Sugai  16 , Yoichi Nakayama  17 , Satoko Yamaguchi  18 , Shinichiro Hayashi  1   2 , Satoru Noguchi  1   2 , Hisateru Tachimori  3 , Naoko Okiyama  19 , Manabu Fujimoto  20   21 , Ichizo Nishino  1   2
Affiliations

Association of Dermatomyositis Sine Dermatitis With Anti-Nuclear Matrix Protein 2 Autoantibodies

Michio Inoue et al. JAMA Neurol. .

Abstract

Importance: Reports on dermatomyositis (DM) sine dermatitis (DMSD) are scarce, and the concept of the disease has not been widely accepted.

Objective: To confirm the existence of DMSD, determine its prevalence, and characterize its serologic features.

Design, setting, and participants: This is a cohort study that reviewed clinical information, laboratory data, and muscle pathology slides from January 2009 to August 2019. We further assessed the follow-up data of 14 patients with DMSD. The median (interquartile range) follow-up period was 34 (16-64) months. Muscle biopsy samples, along with clinical information and laboratory data, were sent to a referral center for muscle diseases in Japan for diagnosis. Of patients whose myopathologic diagnosis was made at the National Center of Neurology and Psychiatry between January 2009 and August 2019, 199 patients were eligible for inclusion. These patients underwent full investigation for DM-specific autoantibodies (against transcriptional intermediary factor γ, Mi-2, melanoma differentiation-associated gene 5, nuclear matrix protein 2 [NXP-2], and small ubiquitin-like modifier activating enzyme ); however, 17 patients were excluded because their muscle fibers did not express myxovirus resistance protein A, a sensitive and specific marker of DM muscle pathology.

Main outcomes and measures: Diagnosis of DMSD was based on the absence of a skin rash at the time of muscle biopsy.

Results: Of the 182 patients, 93 were women (51%) and 46 were children (25%) (<18 years). Fourteen patients (8%) had DMSD and none were clinically diagnosed with DM. Among the 14 patients with DMSD, 12 (86%) were positive for anti-NXP-2 autoantibodies, while the remaining 2 were positive for anti-transcriptional intermediary factor γ and anti-Mi-2 autoantibodies, respectively. Only 28% of patients (47 of 168) with a skin rash were positive for anti-NXP-2 autoantibodies, indicating a significant association between anti-NXP-2 autoantibodies and DMSD (86% [12 of 14] vs 28% [47 of 168]; P < .001). This association was also supported by multivariable models adjusted for disease duration (odds ratio, 126.47; 95% CI, 11.42-1400.64; P < .001).

Conclusions and relevance: Dermatomyositis sine dermatitis does exist and accounts for 8% of patients with DM confirmed with muscle biopsy. Dermatomyositis sine dermatitis is significantly associated with anti-NXP-2 autoantibodies, which contrasts with anti-MDA5 DM, which is typically clinically amyopathic in presentation. It is essential to distinguish DMSD from other types of myositis because DM-specific therapies that are currently under development, including Janus kinase inhibitors, may be effective for DMSD.

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Conflict of interest statement

Conflict of Interest Disclosures: Dr Inoue reported grants from JSPS KAKENHI outside the submitted work. Dr Awano reported personal fees from Biogen Japan Ltd, Eisai Co Ltd, JCR Pharmaceuticals Co, Ltd, Novartis Pharma K. K., Takeda Pharmaceutical Company Limited, Astellas Pharma Inc, and Sarepta Therapeutics outside the submitted work. Dr Tachimori reported grants from Japan Agency for Medical Research and Development, Japan Society for the Promotion of Science, Ministry of Health, Labor, and Welfare, Japan, Japan Science and Technology Agency, and FUJIFILM Corporation outside the submitted work. Dr Nishino reported personal fees from Sanofi and Japan Blood Products Organization and grants from Daiichi-Sankyo outside the submitted work. No other disclosures were reported.

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