Studies on myocarditis in childhood, with special reference to the possible role of immunological process and the thymus in the chronicity of the disease.

Twenty-one cases of idiopathic myocarditis were studied. Fulminant form 1 case, acute fatal form 2 cases, acute benign form 4 cases, recurrent form 1 case. Chronic dilated form 2 cases progressive hypertrophy form 2 cases and asymptomatic and sudden death form was 10 cases. Clinical signs and symptoms of these cases were manifold. Also laboratory findings were nonspecific. Ten cases of latent myocarditis which showed sudden death syndrome were found among 47 cases, progressive hypertrophy form 2 cases and children. Early detection of latent myocarditis is considered to be necessary for preventing sudden death syndrome in school children. The relationship between cardiomyopathy and idiopathic myocarditis was discussed. Two cases of idiopathic myocarditis simulating cardiomyopathy were presented. The pathogenesis of chronicity in idiopathic myocarditis was discussed. Bound gammaglobulin in heart muscle was detected in a case showing progressive hypertrophy of the ventricles. Autopsy results showed a previously undescribed finding that the cases having normal thymus/body weight ratio tended to have markedly increased heart weight but the cases having increased thymus/body weight ratio tended to have near normal heart weight. These results are considered to suggest the possible role of immunity in the chronicity of idiopathic myocarditis.