Family studies of relation between Perthes disease and congenital dislocation of the hip.

A family study of Perthes disease and congenital dislocation of the hip was made in the Faroe Islands, with a population of 40 000. The examination included 1123 sibs and first cousins of 43 probands with Perthes disease, 1942 sibs and first cousins of 59 dislocation probands, and 5205 sibs and first cousins of 172 unaffected matched controls. Both conditions occur with exceptionally high incidences in this population. Thus the incidence of Perthes disease was found to be 41: 10 000 males and 7: 10 000 females, of congenital dislocation of the hip 7: 10 000 males and 59: 10 000 females. These figures are 3 to 4 times higher than those commonly observed in Caucasian populations. Among the 1123 relatives of Perthes probands, we found 10 cases of Perthes disease and 9 cases of dislocation; among the 1942 relatives of dislocation probands, there were 11 cases of Perthes disease and 23 cases of dislocation. Thus both disorders show an accumulation within the same families. On the other hand among the 5205 relatives of probands selected because the hips were unaffected, we found only 3 cases of Perthes disease and 10 cases of dislocation. Considering the conspicuously low familial accumulation of Perthes disease seen in a low-risk population elsewhere (South Wales), the high incidence of the two disorders and the simultaneously strong intrafamilial accumulation in the Faroe population seem to indicate that the search for exogenous influences, specific to this area, should be intensified.