A 4-year-old boy was examined for prolonged bleeding after minor surgery and spontaneous bleeding into his knee joints. Deficiency of coagulation factor VIII was demonstrated during the hematological work-up. This disease is inherited as
A. autosomal dominant
B. autosomal recessive
C. X-linked recessive
D. X-linked dominant with variable penetrance
E. X-linked dominant with maternal imprinting
C
This boy has hemophilia A (congenital deficiency of factor VIII), a bleeding disorder inherited as an X-linked recessive trait. Mothers are carriers of this trait but are asymptomatic. Only boys are affected, but the asymptomatic daughters can be carriers of the trait. It is worth remembering that X-linked dominant diseases are extremely rare. The only major autosomal congenital bleeding disorder is von Willebrand's disease, which can be inherited as an autosomal dominant or recessive trait.
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