Haemophilia A and B are severe inherited bleeding disorders. Haemophilia A is caused by a deficiency of factor VIII. Haemophilia B (also known as Christmas disease) is caused by a deficiency in factor IX.
X-Linked Recessive
Both haemophilia A and B are X-linked recessive diseases. All X chromosomes need to have the abnormal gene to have haemophilia. Males only have one X chromosome and require only one abnormal copy to have the disease. Females have two X chromosomes, so when one copy is affected, they are asymptomatic carriers of the gene.
Therefore, haemophilia A and B primarily affect males. For a female to be affected, they would require an affected father and a mother who is either a carrier or affected.
Features
Both haemophilia A and B are severe bleeding disorders. Patients can bleed excessively in response to minor trauma and are at risk of spontaneous bleeding without any trauma.
Most cases present in neonates or early childhood. It can present with intracranial haemorrhage, haematomas and cord bleeding in neonates.
Spontaneous bleeding into joints (haemarthrosis) such as the ankle, knee or elbow can lead to joint damage and deformity. Bleeding into the muscles can cause compartment syndrome.
Other areas of bleeding include:
- Oral mucosa
- Nosebleeds (epistaxis)
- Gastrointestinal tract
- Urinary tract, causing haematuria
- Intracranial haemorrhage
- Surgical wounds
Diagnosis
Diagnosis is based on bleeding scores, coagulation factor assays and genetic testing.
Management
The affected clotting factors (VIII or IX) can be given by intravenous infusion, either regularly or in response to bleeding. A complication of this treatment is the formation of antibodies (called inhibitors) against the treatment, resulting in it becoming ineffective.
Last updated August 2023
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