What is the primary deficiency in hemophilia A?
Hemophilia A, the commonest hereditary bleeding disorder, is due to a genetic deficiency of plasma factor VIII. Although the inheritance is X-linked recessive, approx-imately 30% of those with the disease acquire it through a spontaneous mutation and, therefore, will present with no family history of hemophilia. Regardless of how the disease is acquired, it is primarily a disease of males.
Its incidence approaches 1 in 5,000 male births. This “classi-cal hemophilia A” should be considered in any male who presents with unexplained and uncontrolled bleeding.
The plasma factor VIII concentration correlates strongly with the degree of bleeding seen. Patients with severe hemophilia have factor VIII levels 1% or less compared with normal. Those with factor levels 2–5% of normal have moderate hemophilia, while patients with factor levels 6–30% of normal have mild disease. It is important to quantify the plasma levels of factor VIII prior to surgery to assess the risk of bleeding. Patients with mild hemophilia will usually bleed excessively only after trauma or during surgery, whereas severe hemophiliacs can bleed sponta-neously 20–30 times a year, usually into joints and muscle.