Inherited combined deficiency of factors XI and XII with von Willebrand's disease.

Combined hereditary deficiency of factors XI (FXI) and XII (FXII) associated with the deficeincy of von Willebrand factor (vWF) in a single patient has not been reported so far in the literature. We report on two brothers of non-Jewish stock with defciency of FXI, FXII and vWF. The family studies disclosed FXI and FXII deficiency in the mother of propositi. A maternal niece had FXII deficiency. The father of propositi had vWF deficiency. This study suggests possible existence of a regulatory factor common to genes specifying FXI and FXII. Associated vWF deficiency is coincidental.