Walsh & Hoyt: Epidemiology

SWS occurs with equal frequency in males and females of all races. Unlike the other phacomatoses in which clear cut hereditary patterns are usually present, the influence of heredity in SWS is not evident. The entire syndrome rarely, if ever, occurs in more than one member of a family. Although several types of chromosome abnormalities have been discovered in individual patients with this syndrome, most patients have normal karyotypes. It is possible that the disease arises from genetic mosaicism, with specific mutations occurring in the disease tissue but not in normal tissues from the same patient.