Objective. Myositis-specific autoantibodies (MSA) define relatively homogenous clinical and immunogenetic patient groups in adults with idiopathic inflammatory myopathies (IIM). This study explores the usefulness of MSA in defining groups of children with myositis. Methods. Sera from 77 children with myositis and other connective tissue diseases were tested for MSA by immunoprecipitation and immunodiffusion. Clinical data were collected and analyzed. Results. The MSA anti-PL-12 (alanyl-transfer RNA synthetase), anti-Jo-1 (histidyl-tRNA synthetase), anti-signal recognition particle, and anti-Mi-2 were each identified in the sera of 12 children with IIM. In these patients, the clinical manifestations, disease courses, and responses to therapy closely resembled those in adults with the same autoantibodies. Conclusion. These observations suggest that the clinical syndromes defined by particular MSA are similar in children and adults with IIM. By defining similar clinical syndromes in children who have MSA, this study provides a basis for future studies of MSA in the idiopathic inflammatory myopathies of childhood, which may be useful in predicting the clinical courses of a subset of these patients and improving their therapy.
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