Autoantibodies to Small Ubiquitin-Like Modifier Activating Enzymes in Japanese Patients with Dermatomyositis

Manabu Fujimoto¹, Takashi Matsushita², Yasuhito Hamaguchi³, Kenzo Kaji³, Minoru Hasegawa¹ and Kazuhiko Takehara⁴, ¹Dermatology, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan, ²Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan, ³Department of Dermatology, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan, ⁴Dermatology, Kanazawa University, Kanazawa, Japan

Meeting: ACR/ARHP Annual Meeting 2012

Keywords: Autoantibodies and dermatomyositis

Session Information

Title: Muscle Biology, Myositis and Myopathies: Clinical and Therapuetic Aspects of Idiopathic Inflammatory Myopathies

Session Type: Abstract Submissions (ACR)

Background/Purpose: Myositis-specific autoantibodies (MSAs) are closely associated with distinct clinical subsets within idiopathic inflammatory myopaties, and thus serve as useful diagnostic tools. Recently, anti-small ubiquitin-like modifier activating enzyme (SAE) autoantibody has been reported as a novel MSA in dermatomyositis (DM) patients. In this study, we detected this autoantibody in a Japanese DM cohort and assessed its clinical correlations.

Methods: In this study, 456 consecutive Japanese patients with DM (11 children, 455 adults) including 373 with classic DM and 83 with clinically amyopathic DM (CADM) were examined. Controls included 62 patients with polymyositis, 108 with systemic lupus erythematosus, 433 with systemic sclerosis, and 124 with interstitial lung disease (ILD) alone. Autoantibodies were detected by immunoprecipitation assays using ³⁵S-methionine-labeled or unlabeled K562 cell extracts and western blotting using anti-SAE1/2 antibodies.

Results: Sera from 7 (1.5%) DM patients immunoprecipitated 90 and 40 kDa proteins, and were confirmed to react with SAE by western blotting. One patient had juvenile DM, while the other 6 had adult DM (median age of onset, 67 years). None of the control sera had this antibody. Heliotrope rash, Gottrons papules, periungual lesions, V signs, and Shawl signs were observed in 57%, 86%, 100%, 57%, and 86%, respectively. Consistent with a UK cohort study¹⁾, skin manifestations preceded muscle involvement in 86% patients with anti-SAE antibodies. Systemic features were present in 57% of patients inbcluding 2 patients with severe dysphagia. In addition, chronic ILD was substantially higher in anti-SAE-positive DM patients (71%) than those negative (34%).

Conclusion: Consisitent with the UK cohort study, this study confirmed that anti-SAE antibody is specific for DM and that anti-SAE antibody characteristically occur in patients who present with CADM first and then progress to develop myositis with a high frequency of systemic features, including dysphagia. Our study also revealed a high frequency of ILD in Japanese DM patients with anti-SAE antibody.

1) Betteridge ZE et al. Ann Rheum Dis. 2009;68:1621-5.

Disclosure:

M. Fujimoto,
None;

T. Matsushita,
None;

Y. Hamaguchi,
None;

K. Kaji,
None;

M. Hasegawa,
None;

K. Takehara,
None.

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