Hemophilia is the most common X-linked genetic disease, occurring in about 1.25 in 10,000 live male births. Hemophilia A is five times more common than hemophilia B. Hemophilia causes abnormal bleeding because of a specific clotting factor malfunction. After a person with hemophilia forms a platelet plug at a bleeding site, clotting factor deficiency impairs the capacity to form a stable fibrin clot.

The mild form of hemophilia frequently goes undiagnosed until adulthood because the patient with a mild deficiency doesn’t bleed spontaneously or after minor trauma but has prolonged bleeding if challenged by major trauma or surgery. Postoperative bleeding continues as a slow ooze or ceases and starts again up to 8 days after surgery.

Moderate hemophilia causes symptoms similar to those of severe hemophilia but produces only occasional spontaneous bleeding episodes.

Severe hemophilia causes spontaneous bleeding. The first sign of severe hemophilia is usually excessive bleeding after circumcision. Later, spontaneous bleeding or severe bleeding after minor trauma may produce large subcutaneous and deep intramuscular hematomas.

Bleeding into joints and muscles causes pain, swelling, extreme tenderness and, possibly, permanent deformity. Bleeding near peripheral nerves may cause peripheral neuropathies, pain, paresthesia, and muscle atrophy.

If bleeding impairs blood flow through a major vessel, it can cause ischemia and gangrene. Pharyngeal, lingual, intracardial, intracerebral, and intracranial bleeding may lead to shock and death.