Genetic studies on familial leukemia

Familial leukemia in Japan was studied. Among 20 families where familial leukemia occurred in siblings, in 6 of them (30%) the parents were first cousins, in 2 (10%) each they were first cousins once removed and second cousins, while among 200 families where nonfamilial leukemia occurred, only in 9 of them (4.5%) were the parents first cousins, indicating that incidence of consanguineous marriage is high in familial leukemia in siblings. It was also noted that the age of the patient at the time of onset of familial leukemia in children of first cousin parents was lower than that of cases whose parents were not related. From these findings it is suggested that genetic factors play an important role in the etiology of familial leukemia occurring in siblings.