Rheumatic Fever in Siblings

Most attacks of rheumatic fever have only one or two major clinical manifestations. The possibility that the host is genetically predisposed to individual manifestations was explored by determining whether siblings with rheumatic fever tend to have the same manifestations and sequelae. Sixty-seven sibling pairs were studied. Data of the clinical manifestations during the first attack and of the subsequent sequelae were collected for each member "blindly." The concordance of manifestations and sequelae within sibling pairs was then evaluated statistically. Concordance was significant for chorea (p less than 0.01) and for joint involvement (p less than 0.05). Cardiac involvement was concordant when gauged by the presence of residual heart disease (p less than 0.05) and discordant when gauged by the less reliable method of retrospective diagnosis of carditis. Biases, infectious agent and environment were found to be unlikely reasons for the concordance of manifestations. The exclusion of these factors suggests that the concordance is caused by genetic variation.