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Clinical characteristics of Japanese patients with anti-PL-7 (anti-threonyl-tRNA synthetase) autoantibodies

S. Sato¹, M. Hirakata¹, M. Kuwana², K. Nakamura¹, A. Suwa¹, S. Inada³, T. Mimori⁴, Y. Ikeda¹

¹Department of Internal Medicine and ²Institute for Advanced Medical Research, Keio University, School of Medicine, Tokyo; ³Division of Rheumatic Diseases, Tokyo Metropolitan Ohtsuka Hospital, Tokyo; ⁴Department of Rheumatology and Clinical Immunology, Kyoto University Graduate School of Medicine, Kyoto, Japan

ABSTRACT
Objective
The clinical and laboratory features of seven Japanese patients with anti-aminoacyl-tRNA synthetase (ARS) autoantibodies against PL-7 (anti-threonyl-tRNA synthetase) were analyzed and compared with previously published findings.

Methods
Serum samples from 1,135 Japanese patients with various autoimmune diseases were screened for anti-PL-7 antibodies using RNA and protein immunoprecipitation assays. The patients whose sera contained anti-PL-7 antibodies were assessed regarding clinical symptoms and clinical course.

Results
Sera from seven patients were found to have anti-PL-7 antibodies. These autoantibodies were associated with polymyositis/dermatomyositis (PM/DM) and/or interstitial lung disease (ILD). The clinical diagnoses of these seven patients were PM - systemic sclerosis (SSc) overlap (5 patients), DM (1 patient) and idiopathic pulmonary fibrosis (IPF) (1 patient). All patients had ILD with a chronic course and six also had arthritis (85%) and five sclerodactyly (71%).

Conclusions
These results indicate that anti-PL-7 autoantibodies are closely associated with PM-SSc overlap as well as ILD, arthritis and sclerodactyly in our series of Japanese patients.

Key words
Polymyositis/dermatomyositis (PM/DM), interstitial lung disease (ILD), anti-aminoacyl-tRNA synthetases (ARS) antibodies.

Please address correspondence and reprint requests to: Shinji Sato, MD, Department of Internal Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
E-mail: shins@sc.itc.keio.ac.jp