Hemophilia A – Causes, Symptoms and Treatment
Hemophilia A is an inherited bleeding disorder caused by a deficiency of clotting factor VIII. Those affected tend to experience prolonged and excessive bleeding.
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Hemophilia A is an inherited bleeding disorder caused by a deficiency of clotting factor VIII. Those affected tend to experience prolonged and excessive bleeding.
What is Hemophilia A?
Hemophilia A is the most common form of hemophilia and is an inherited disorder affecting blood clotting. It is caused by a deficiency or dysfunction of clotting factor VIII, which is essential for normal coagulation. Without sufficient levels of this factor, the body cannot effectively stop bleeding. The condition primarily affects males, as it follows an X-linked recessive inheritance pattern.
Causes
Hemophilia A is caused by a mutation in the gene encoding factor VIII, located on the X chromosome. Because males have only one X chromosome, a single faulty copy of the gene is sufficient to cause the disease. Females with a mutation on one of their two X chromosomes are typically carriers and usually experience no or only mild symptoms.
- X-linked recessive inheritance pattern
- Point mutations, deletions, or inversions in the F8 gene
- Approximately 30% of cases have no family history (de novo mutations)
Severity Classification
Hemophilia A is classified into three severity levels based on the residual factor VIII activity in the blood:
- Mild: Factor VIII activity 5–40% – bleeding usually only occurs after injury or surgery
- Moderate: Factor VIII activity 1–5% – occasional spontaneous bleeding possible
- Severe: Factor VIII activity below 1% – frequent spontaneous bleeding, particularly into joints and muscles
Symptoms
The hallmark symptom of hemophilia A is prolonged or excessive bleeding. Typical symptoms include:
- Hemarthroses – bleeding into joints (especially the knees, elbows, and ankles), which can lead to pain and long-term joint damage
- Muscle bleeds (hematomas)
- Prolonged bleeding after injuries, surgeries, or tooth extractions
- Spontaneous nosebleeds or gum bleeding
- In severe cases: life-threatening internal bleeding or intracranial hemorrhage
Diagnosis
Diagnosis is made through laboratory coagulation testing:
- Measurement of factor VIII activity in the blood
- Prolonged aPTT (activated partial thromboplastin time) with normal prothrombin time (PT)
- Genetic testing to identify the causative mutation
- Prenatal diagnosis and carrier testing in families with a known history of the condition
Treatment
Treatment of hemophilia A focuses on replacing the missing factor VIII and preventing or managing bleeding episodes.
Factor VIII Replacement Therapy
The standard treatment is intravenous infusion of factor VIII concentrate, either derived from human plasma or produced by recombinant technology. It can be used as on-demand therapy (for acute bleeding) or as prophylaxis (regular infusions to prevent bleeds).
Emicizumab (Hemlibra)
Emicizumab is a bispecific antibody that mimics the function of factor VIII and can be administered subcutaneously. It represents an important treatment option, particularly for patients who have developed inhibitors (antibodies against factor VIII).
Inhibitor Development
Approximately 25–30% of patients with severe hemophilia A develop inhibitors against factor VIII, which significantly complicates treatment. In these cases, bypassing agents or emicizumab are used to manage bleeding.
Gene Therapy
Recent advances in gene therapy (e.g., valoctocogen roxaparvovec) allow a functional copy of the F8 gene to be delivered to liver cells, enabling long-term factor VIII production. This therapy has been approved for selected adult patients with severe hemophilia A.
References
- Srivastava A. et al. – WFH Guidelines for the Management of Hemophilia, 3rd Edition. Haemophilia 2020; 26(S6): 1–158. World Federation of Hemophilia (WFH).
- Lenting PJ, Denis CV, Christophe OD – Emicizumab, a bispecific antibody recognizing coagulation factors IX and X. J Thromb Haemost 2017; 15(10): 1894–1898.
- European Medicines Agency (EMA) – Product information for Roctavian (Valoctocogen Roxaparvovec), 2022.
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Related search terms: Hemophilia A + Haemophilia A + Hemophilia type A