Myocarditis in juvenile rheumatoid arthritis.

Three children are described who have had myocarditis as part of juvenile rheumatoid arthritis (JRA). The diagnosis was established by the appearance of cardiomegaly or congestive heart failure or both in the absence of substantial pericardial effusion or extra cardiac cause. Myocarditis, in these cases, occurred on a background of severe, active systemic disease. No pathologic specimens from hearts of acute cases are available, but an autopsy specimen of one child who died after two months of treatment with high doses of steroids showed diffuse changes typical of the "dilated ventricle" type of cardiomyopathy. Treatment with high doses of adrenocorticosteroids has been rapidly successful in controlling the acute phase, while digoxin must be used with extreme care because of high incidence of toxicity to glycosides.