Antisynthetase syndrome (ASS) is a rare chronic autoimmune disorder (2-3 times more common in women than in men), associated with interstitial lung disease (the most important feature), dermatomyositis (DM), and polymyositis (PM). The cause of ASS is unknown. Recent developments in immunology have improved our knowledge and it is now possible to classify ASS according to the presence of myositis specific autoantibodies. The hallmark of ASS is the presence of serum autoantibodies directed against aminoacyl-tRNA synthetases (anti-ARS involved in protein synthesis). ASS is due to IgG antibodies directed against the enzyme synthase. Antisynthetase antibodies (ASAb) include: anti-histidyl- (anti-Jo-1, being the best known), anti-threonyl- (anti-PL-7), anti-alanyl (anti-PL-12), anti-isoleucyl- (anti-OJ), anti-glycyl- (anti-EJ), anti-asparaginyl- (anti-KS), anti-Wa, anti-tyrosil- (anti-YRS), anti-phenylalanyl-transfer RNA synthetase (anti-Zo), and anti-signal recognition particle (anti-SRP). Anti-Jo-1 is the most common ASAb (in ~20-30% of PM/DM patients).
