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Hemophilia is a rare bleeding disorder in which the blood doesn't clot properly. People with it can bleed too much after an injury or surgery — and can also bleed suddenly inside the body, into joints, muscles and organs.
What's missing
Blood contains proteins called clotting factors that help form clots. People with hemophilia have low levels of one of them, usually factor VIII (8) or factor IX (9). The less factor there is, the more likely bleeding is — and the more serious.
| Type | Cause |
|---|---|
| Hemophilia A ("classic" hemophilia) | Too little factor VIII |
| Hemophilia B ("Christmas disease") | Too little factor IX |
Why it runs in families — and mostly in males
Most hemophilia is inherited, caused by a change (mutation) in a gene that carries the instructions for a clotting factor. Those genes are on the X chromosome.
- People born male have one X chromosome (from their mother) and one Y. One changed gene on their single X is enough to cause hemophilia — which is why it is much more common in males.
- People born female have two X chromosomes and usually have hemophilia only if both carry the change, or if one does and the other is missing or inactive. With the change on one X, they are carriers: they may have some symptoms and can pass it to their children.
A family history also raises the risk. Acquired hemophilia, which is not inherited and is rare, happens when the body makes autoantibodies that disable a clotting factor — linked to pregnancy, immune disorders, cancer or allergic reactions to some medicines, or to no known cause.
Signs
- Bleeding into joints — swelling, pain or tightness, often in the knees, elbows and ankles
- Bruising, and bleeding into muscle and soft tissue that pools as a hematoma
- Bleeding of the mouth and gums that is hard to stop, including after losing a tooth
- Bleeding after circumcision or after shots
- Bleeding in an infant's head after a difficult delivery
- Blood in the urine or stool, and frequent, hard-to-stop nosebleeds
- In severe cases, bleeding in the brain, which can cause brain damage and be life-threatening
Diagnosis
A provider asks about symptoms and family history, looks for signs such as bruising, and orders blood tests of clotting; if blood doesn't clot properly, clotting factor tests show the type and severity. Genetic testing of the factor VIII and IX genes can identify carriers before a pregnancy, test a fetus, or test a newborn in families with hemophilia.
Treatment
The best treatment is replacing the missing factor, usually by injection into a vein — factor made from donated blood, or recombinant factor made in a lab. It treats bleeding episodes and, in severe hemophilia, can be given regularly to prevent them; many people learn to inject it at home. Other medicines release stored factor VIII, stand in for its function, or stop clots from breaking down. Physical therapy helps joints damaged by bleeding, and care at a hemophilia treatment center can prevent serious problems.
Sources
Based on "Hemophilia," MedlinePlus, National Library of Medicine, drawing on the Centers for Disease Control and Prevention; a work of the United States government in the public domain.
Лицензия: CC0 1.0 (общественное достояние) · По материалам medlineplus.gov
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