Idiopathic inflammatory myopathy: autoantibody update

Several defined, specific autoantibodies have been associated with polymyositis and dermatomyositis. These include autoantibodies to at least six of the aminoacyl-transfer-ribonucleic-acid synthetases; to the signal recognition particle; to the protein complexes labeled Mi-2 and PM-Scl; and several autoantibodies, such as anti-U1nRNP and anti-Ro/SSA, that have recognized associations with other conditions. These autoantibodies are a continuing area of interest. Recent studies have involved the clinical implications of these autoantibodies, and their potential significance for etiology and pathogenesis of the disease. This report will review recent studies of myositis autoantibodies and their clinical associations, both extramuscular features, such as interstitial lung disease and aspects of the myositis itself. New myositis autoantibodies continue to emerge, which may have clinical utility. Several have been associated with dermatomyositis, including juvenile dermatomyositis, which has a low frequency of traditional myositis autoantibodies. There is also new information regarding the antigenic targets of anti-Mi-2 and anti-PM-Scl, two of the earliest recognized myositis autoantibodies. New evidence over the past few years has challenged old concepts of the relationship of autoantibodies to the pathogenesis of myositis, and has suggested potential new mechanisms for the origin of the associated autoantibodies. Despite this progress, the reason for production of the autoantibodies and their role in tissue injury remain unknown.