Summary
Antisynthetase syndromes are a subgroup of idiopathic inflammatory diseases, characterized by the association of inflammatory myopathy, polyarthritis, Raynaud's phenomenon and hyperkeratosis with fissures, and by the presence of antisynthetase antibodies, anti-Jo-1 being the most frequent. More than 200 cases have been reported in the literature and the syndrome is most frequent in Southern Europe. It affects all age groups but is more common in females than males, with a sex ratio of 3:2. Inflammatory myopathy is frequently associated with pulmonary involvement, usually interstitial. It may be acute and the inaugural manifestation of the disease, or progressive and appear during follow-up. It initially manifests as a dry cough followed by exertional dyspnea. Myositis is a constant feature but severity varies and it may be secondary to pulmonary involvement. In some cases, myositis is associated with dysphagia. Joint involvement is variable with polyarthralgia being the most common finding. Raynaud's phenomenon is observed frequently during the initial phase of the disease but is rarely severe. Fever and hyperkeratotic fissures may complete the clinical picture. The interaction between enzymes which acetylate tRNAs and some viruses which use these enzymes when they replicate within host cells may result in production of the antisynthetase antibodies causing the disease. Among the seven known antibodies, anti-Jo-1 is the most frequently identified. Following the clinical diagnosis, systematic screening for anti-Jo-1 should be performed using indirect immunofluorescent assays. Detection of anti-Jo1 antibodies should lead to screening for pulmonary involvement, using functional respiratory exploration (FRE) and high-resolution computed tomography, to allow for early diagnosis. Differential diagnoses mainly include rheumatoid arthritis and scleroderma (see this term). Hypersensitivity pneumonitis and acute forms of pulmonary idiopathic fibrosis (see these terms), as well as respiratory infections and alveolar hemorrhage should be included in the differential diagnosis for acute pulmonary forms associated with fever. Corticosteroids appear to alleviate the joint, muscular and general symptoms, as well as some forms of pulmonary disease. Immunosuppressive drugs are required for steroid-resistant patients. Therapies involving corticosteroids and intravenous immunoglobulin improve endurance and strengthen inspiratory muscles. Pulmonary involvement responses to treatment are unpredictable. In some cases involving young patients, disease progression may lead to an indication for pulmonary transplantation. The severity of pulmonary involvement determines the outcome of the disease. In more than a third of cases, it may evolve to fibrosis with respiratory failure. Early management may lessen the severity of the disease course and improve outcome. *Author: Dr I. Tillie-Leblond (October 2008)*.
