Mixed connective tissue disease in childhood. A clinical and serologic survey.

Mixed connective tissue disease is a syndrome with overlapping clinical features of SLE, scleroderma, and polymyositis. Only one other child with MCTD has been described in detail. In this study 14 children with MCTD are described. Each had overlapping clinical findings that evolved over an extended period of observation, and all 14 had high serum titers of speckled ANA and antibodies to RNP. A serologic survey of 127 children with various rheumatic diseases confirmed the specificity of high titer of speckled ANA and antibodies to RNP for MCTD in children. Significant cardiac and renal involvement, and thrombocytopenia, may be more common in affected children than in adults with MCTD, may lead to longer therapy with higher doses of a corticosteroid, and may contribute to a more serious prognosis than in adults.