Pediatric-onset mixed connective tissue disease

One of the reasons why MCTD remains such an enduring focus must be related to the relish that rheumatologists bring to an apparently insolvable controversy. Although perhaps less a disease than a process, labeling a child with MCTD provides the possibility of a roadmap for the clinician as the child and his or her problems progress, regress, and change. Pediatric-onset MCTD and adult-onset MCTD look similar, at least in the beginning, with high rates of arthralgia, Raynaud's disease, fatigue, arthritis, and hand swelling. Although not benign, pediatric-onset MCTD carries less mortality than pediatric-onset SLE or adult-onset MCTD, probably because pulmonary hypertension seems to be less of a problem in pediatric MCTD than in adult MCTD, as far as can be determined on the basis of medium-term follow-up studies. From the authors' series, children tend to do well with a favorable outcome 82% of the time, although disease remission is uncommon (3%). Furthermore, patients who have pediatric-onset MCTD do well functionally, as measured by Steinbrocker class. Additionally, 77% are students or are employed. The most frequent presentation included manifestations that were myositis-like. Like Tiddens and colleagues [10], the authors observed a shift toward scleroderma over time, although not to the same degree that they did. A lot can be learned from the authors' pediatric patients regarding this elusive concept. Perhaps more useful for clinical decision-making than nosologically satisfying, MCTD as a diagnostic label in children may provide insight as more is learned about HLA associations and autoantibody specificity. Defining clinical outcomes among patients who have pediatric-onset MCTD requires long-term studies of 20 years or more because most of the authors' pediatric patients continue to have active disease and change, even as they graduate from pediatric to adult rheumatology centers.