What is the primary antibody found in polymyositis?

In polymyositis, the primary antibody that is commonly associated with the condition is the anti-Jo-1 antibody. This autoantibody is directed against histidyl-tRNA synthetase and is often found in patients with polymyositis and dermatomyositis, indicating an underlying autoimmune process. The presence of anti-Jo-1 is significant not only for the diagnosis but also for its association with the clinical features of the disease, such as interstitial lung disease and myopathy.

Understanding the context of autoantibodies in autoimmune myopathies is important. While anti-histone antibodies are typically associated with drug-induced lupus and systemic lupus erythematosus, and Scl-70 antibodies are related to systemic sclerosis, anti-Ro (SSA) antibodies are primarily seen in Sjögren's syndrome and lupus. These distinctions highlight why anti-Jo-1 is specifically relevant for diagnosing polymyositis over the other antibodies listed.