Key Clinical Updates in Congenital Disorders of Coagulation
While phase 3 clinical trials of gene therapy for hemophilia A and B have to date been restricted to patients 18 years of age and older, the results look extremely promising.
ESSENTIALS OF DIAGNOSIS
Hemophilia A: congenital deficiency of coagulation factor VIII.
Hemophilia B: congenital deficiency of coagulation factor IX.
Recurrent hemarthroses and arthropathy.
Risk of development of inhibitory antibodies to factor VIII or factor IX.
Many older patients received blood products contaminated with HIV or hepatitis C virus.
The frequency of hemophilia A is ~1 per 5000 live male births, whereas hemophilia B occurs in ~1 in 25,000 live male births. Inheritance is X-linked recessive, leading to affected males and carrier (affected) females with variable bleeding tendencies. Daughters of all affected males are obligate carriers. There is no race predilection. Factor activity testing is indicated for male infants with a hemophilic maternal pedigree who are asymptomatic or who experience excessive bleeding, for all daughters of affected males (100% chance of being affected) and carrier mothers (50% chance of being affected), and for otherwise asymptomatic adolescents or adults who experience unexpected excessive bleeding with trauma or invasive procedures.
Inhibitors to factor VIII will develop in approximately 20–25% of patients with severe hemophilia A, and inhibitors to factor IX will develop in less than 5% of patients with severe hemophilia B. The risk of development of an inhibitor to factor VIII or factor IX is highest in patients with severe hemophilia who have a sibling in whom inhibitor formation occurred; the characteristics of initiation of administration of factor replacement in childhood, as well as mutation type, also may be influential. Recent data suggest that recombinant products may have an increased risk of inhibitor formation than products made from pooled plasma.
A substantial proportion of older patients with hemophilia acquired infection with HIV or HCV or both in the 1980s due to exposure to contaminated factor concentrates and blood products.
Severe hemophilia (factor VIII activity less than 1%) presents in infant males or in early childhood with spontaneous bleeding into joints, soft tissues, or other locations. Spontaneous bleeding is not common in patients with mild hemophilia (factor VIII activity greater than 5%), but bleeding is common with a significant hemostatic challenge (eg, surgery, trauma). Intermediate clinical symptoms are seen in patients with moderate hemophilia (factor VIII activity 1–5%). Female carriers of hemophilia can have a wide range of factor VIII activity and therefore have variable bleeding tendencies.
Significant hemophilic arthropathy is usually avoided in patients who have received long-term prophylaxis with factor concentrate starting in early childhood, whereas joint disease is common in adults who have experienced recurrent hemarthroses. Patients tend to have one ...