Anti-
aminoacyl-tRNA synthetase (ARS)
antibodies (anti-Jo-1, anti-PL-7, anti-PL-12, anti-EJ, anti-KS, anti-OJ, anti-Ha, and anti-Zo antibodies) are found in 25 to 40% of
myositis patients. The patients with these
antibodies have anti-
synthetase syndrome with one or more of the following clinical features:
myositis,
interstitial lung disease,
arthritis,
fever, Raynaud's phenomenon, and mechanic's hands. In Japan, health insurance coverage of treatments for patients in whom the "anti-ARS
antibodies," anti-Jo-1, anti-PL-7, anti-PL-12, anti-EJ, and anti-KS are detected by
enzyme-linked
immunosorbent assay was approved by the Ministry of Health, Labour and Welfare in 2014. Recently, clinical features have been discovered to be heterogeneous. Patients with the anti-PL-7, anti-PL-12, anti-KS, and anti-OJ
antibodies exhibit
interstitial lung disease rather than
myositis.
Interstitial lung disease is related to the prognosis of this syndrome. Regarding histopathological findings of the muscle, perimysial connective tissue fragmentation with positive staining for
alkaline phosphatase is the characteristic feature. Myonuclear actin filament inclusions are also detected. A recent work demonstrated that immunization of mice with
histidyl-tRNA synthetase results in muscle
inflammation consistent with
myositis. These findings promote understanding of the pathological mechanism of the development of
myositis associated with anti-ARS
antibodies.