Seven autoantibodies directed against synthetases have been identified to date, the best known being anti-Jo1. Synthetases play a vital role in protein synthesis by catalyzing the acetylation of transfer RNAs (tRNAs). The most common form of antisynthetase syndrome is characterized by anti-Jo1 production, interstitial lung disease (ILD), inflammatory muscle disease, and, in many cases, fever, polyarthritis, Raynaud's phenomenon, and thick cracked skin on the fingers (mechanic's hands). The interstitial lung disease is generally of the "usual interstitial pneumopathy" type and shares similarities with idiopathic pulmonary fibrosis or scleroderma-related pulmonary disease. It governs the prognosis of the disease, being associated with an excess mortality rate of about 40%. The pathogenic mechanisms underlying antisynthetase syndrome remain unknown but may involve cell-mediated immunity. The treatment is not standardized. The ILD responds to glucocorticoids in some patients but requires other immunosuppressant drugs in others.