Perthes disease affecting three female first-degree relatives

Perthes disease has an incidence of 1 in 4,750 live births (1 in 3,000 boys, but only 1 in 11,800 girls). Although there is evidence for a genetic predisposition to Perthes disease, more than two family members are rarely affected. We report the first recorded case of Perthes disease affecting three female first-degree relatives.