Hemophilia

Hemophilia is an inherited disorder in which one of the blood's clotting factors is deficient, so the clotting cascade cannot complete and bleeding is prolonged. The two main types are hemophilia A (a lack of factor VIII, the commoner form) and hemophilia B (a lack of factor IX). Both are caused by changes on the X chromosome, so they almost always affect boys and men, while women can be carriers and sometimes bleed mildly. Severity depends on how much clotting factor is present: severe hemophilia causes spontaneous bleeding, particularly into joints (which over time can damage them) and muscles, while milder forms mainly cause excessive bleeding after injury, surgery or dental work. Typical features are large bruises, prolonged bleeding from cuts, swollen and painful joints from internal bleeding, and, most dangerously, bleeding inside the head or abdomen after injury. On testing, the aPTT clotting time is prolonged while the PT and platelet count are normal, and the diagnosis is confirmed by measuring the specific factor. Treatment replaces the missing factor — on demand for bleeds or regularly to prevent them — and modern therapies mean most people with hemophilia lead full, active lives.

• aPTT — prolonged (the intrinsic pathway is affected).
• Prothrombin time (PT) — normal, which helps localise the problem.
• Platelet count — normal (distinguishing it from platelet disorders).
• Fibrinogen — normal.
• Specific factor assay (factor VIII or IX) — low; confirms the type and severity.
• Genetic testing — identifies the change and helps carrier and family testing.

• Large or deep bruises
• Prolonged bleeding after cuts, injury, surgery or dental work
• Swollen, painful joints from bleeding into them (knees, elbows, ankles)
• Bleeding into muscles
• Nosebleeds that are hard to stop
• Blood in urine or stool
• In severe cases, spontaneous bleeding; rarely, dangerous bleeding in the head or abdomen after injury