Juvenile idiopathic arthritis in multicase families

Objective To characterize juvenile idiopathic arthritis (JIA) patients from multicase families. Methods The study series comprised 80 affected siblings belonging to 37 families. C omparisons were made with a population-based series of JIA patients from Fi nland and with a sibling series from the United States. Results The distribution of c cases according to onset type was similar in the sibl ing and population-based series. The age at diagnosis was significantly low er in the sibling series (4.8 years vs 7.4 years; p < 0.001). There was mor e infra-pair similarity in onset and course types in the United Stares seri es compared To the Finnish series and the proportion of girls was higher in the former: Conclusion The only significant difference between familial and sporadic cases,with JI A is an earlier onset of disease in familial cases. There is no essential d ifference in clinical features of the disease between patients in the multi case and sporadic groups. Differences between the Finnish and US series may be due to selection bias in the latter.