Haemophilia A – Comprehensive Medical Guide
Overview
Haemophilia A (also spelled hemophilia A) is an inherited bleeding disorder caused by a deficiency of clotting factor VIII. Without enough functional factor VIII, blood does not clot properly, leading to prolonged or spontaneous bleeding.
Who it affects
- Almost exclusively males, because the gene that produces factor VIII is located on the X chromosome.
- Females can be carriers and occasionally exhibit mild symptoms if they have two affected X‑chromosomes (rare) or due to skewed X‑inactivation.
Prevalence
- Approximately 1 in 5,000–6,000 male births worldwide develop haemophilia A.[1][2]
- In the United States, the CDC estimates about 20,000 individuals live with haemophilia A, the most common type of hemophilia.[3]
Symptoms
Bleeding patterns vary by severity (mild, moderate, severe) and can change with age.
General symptoms
- Spontaneous joint bleeds (hemarthrosis) – most common in moderate and severe disease. Pain, swelling, and reduced range of motion in knees, elbows, ankles, and wrists.
- Prolonged bleeding after minor cuts, dental work, or surgery.
- Deep tissue bleeds – can present as bruising that feels unusually firm or “hard” under the skin.
- Bleeding into muscles – causes sudden pain and swelling, may mimic a muscle strain.
Symptoms by severity
| Severity | Factor VIII activity | Typical symptoms |
|---|---|---|
| Severe | <1 % | Frequent spontaneous joint/muscle bleeds, bleeding into the brain (intracranial hemorrhage), prolonged bleeding from minor injuries. |
| Moderate | 1–5 % | Bleeding after trauma or surgery, occasional spontaneous joint bleeds, prolonged menstrual bleeding in carrier females. |
| Mild | 5–40 % | Bleeds only after significant trauma, surgery, or dental procedures; may go undiagnosed until adulthood. |
Other possible signs
- Blood in urine or stool.
- Bleeding gums.
- Excessive nosebleeds (epistaxis).
- Bruising without clear cause.
- In newborns, bleeding from the umbilical stump that does not stop after routine care.
Causes and Risk Factors
Genetic cause
Haemophilia A is caused by mutations in the F8 gene, which encodes clotting factor VIII. Over 300 different mutations have been identified, ranging from small deletions to large inversions.
Inheritance patterns
- X‑linked recessive – a mother who carries one mutated copy has a 50 % chance of passing the disease to each son and a 50 % chance of making a carrier daughter.
- De novo mutations – up to 30 % of cases arise from a new mutation in the mother’s egg or the father’s sperm; there is no family history.
Risk factors
- Having a male relative (brother, uncle, grandfather) with haemophilia A.
- Being a carrier female (identified by genetic testing).
- Ethnic groups with founder mutations (e.g., some populations in the United Kingdom, the United States, and the Middle East have slightly higher prevalence).
Diagnosis
Diagnosis involves a combination of clinical assessment and laboratory testing.
Screening tests
- Activated Partial Thromboplastin Time (aPTT) – prolonged in hemophilia because factor VIII is part of the intrinsic pathway.
- Prothrombin Time (PT) – usually normal, helping to differentiate from other clotting disorders.
Specific factor assays
Quantitative measurement of factor VIII activity (FVIII:C) is the definitive test.
- Severe: <1 % activity.
- Moderate: 1–5 % activity.
- Mild: 5–40 % activity.
Genetic testing
DNA analysis of the F8 gene confirms the mutation, guides carrier testing, and is useful for prenatal counseling.
Additional evaluations
- Joint imaging (ultrasound, MRI) if hemarthrosis is suspected.
- Screening for inhibitors (antibodies that neutralize infused factor VIII) using the Bethesda assay—critical before starting replacement therapy.
Treatment Options
Treatment aims to prevent or control bleeding, maintain joint health, and improve quality of life. Therapy is individualized based on severity, lifestyle, and inhibitor status.
Replacement therapy
- Plasma‑derived factor VIII concentrates (e.g., Humate‑P, Kogenate). Derived from pooled human plasma; viral inactivation steps minimize infection risk.
- Recombinant factor VIII products (e.g., Advate, Elocta, Nuwiq). Manufactured without human plasma, decreasing infection risk and allowing for higher purity.
Administration is usually intravenous, either on‑demand (when bleeding starts) or prophylactically (regular doses to prevent bleeds).
Long‑acting (extended half‑life) products
Modified molecules (e.g., Eftrenonacog alfa, Alprostadil) have half‑lives 1.5–2× longer, allowing dosing every 3–5 days instead of every other day.
Emicizumab (Hemlibra)
A bispecific monoclonal antibody that mimics factor VIII activity. Administered subcutaneously weekly, bi‑weekly, or monthly. Effective for patients with inhibitors and for many without inhibitors.[4]
Bypassing agents (for inhibitors)
- Activated prothrombin complex concentrate (aPCC, FEIBA).
- Recombinant activated factor VII (rFVIIa, NovoSeven).
These agents promote clotting without needing factor VIII and are used when inhibitors neutralize replacement therapy.
Adjunctive measures
- Antifibrinolytics (tranexamic acid, epsilon‑aminocaproic acid) – especially useful for oral or dental bleeds.
- Physical therapy – to maintain joint range of motion and muscle strength after bleeds.
- Desmopressin (DDAVP) – only effective in mild haemophilia A (factor VIII levels ≥5 %). It releases stored factor VIII from endothelial cells.
Lifestyle & preventive steps
- Wear protective helmets and padded gear during sports.
- Avoid high‑impact activities that stress joints (e.g., basketball, soccer) unless on a proven prophylactic regimen.
- Maintain good oral hygiene; schedule dental procedures with the haemophilia care team.
Living with Haemophilia A
Daily management tips
- Keep a bleed diary – record date, location, trigger, treatment used, and recovery time. Helps the care team adjust prophylaxis.
- Store factor concentrate at home – follow manufacturer refrigeration guidelines; many now come in room‑temperature formulations.
- Learn self‑infusion – most patients become proficient by age 8–12 with guidance from a hemophilia nurse.
- Stay active safely – low‑impact activities such as swimming, cycling, or walking promote joint health without high injury risk.
- Regular check‑ups – at least annually with a comprehensive hemophilia center for inhibitor screening, joint imaging, and psychosocial support.
Psychosocial aspects
Living with a chronic bleeding disorder can cause anxiety, especially around school, work, or travel. Support groups (e.g., World Federation of Hemophilia, local patient associations) and counseling services are valuable resources.
Reproductive considerations
- Male patients with haemophilia A can father children; they will transmit the mutated X‑chromosome to all daughters (who become carriers) and none of their sons.
- Carrier females may experience menorrhagia; treatment options include hormonal therapy and, if severe, factor replacement during menstruation.
- Pregnant carriers should receive prenatal genetic counseling and possibly amniocentesis or chorionic villus sampling to determine fetal status.
Prevention
Because haemophilia A is genetic, the primary prevention strategy is informed family planning.
- Genetic counseling for at‑risk couples – discuss carrier testing, reproductive options (pre‑implantation genetic diagnosis, donor eggs/sperm).
- Early prophylaxis – starting regular factor replacement in infancy dramatically reduces joint damage and improves long‑term mobility.[5]
- Vaccination – ensure patients receive hepatitis A/B and other routine vaccines; avoid live vaccines administered intramuscularly without proper factor coverage.
Complications
If bleeding is not adequately controlled, several serious complications can arise.
- Hemophilic arthropathy – chronic joint damage from repeated hemarthroses; leads to pain, stiffness, and reduced mobility.
- Inhibitor development – neutralizing antibodies against factor VIII occur in ~30 % of severe patients, making standard replacement ineffective.
- Intracranial hemorrhage – especially in severe disease; a life‑threatening emergency.
- Chronic anemia – from frequent low‑grade bleeding.
- Infectious disease transmission – historically a concern with plasma‑derived products; modern viral inactivation has reduced risk to <0.001 %.
- Psychological impact – depression, anxiety, and reduced health‑related quality of life are reported more often than in the general population.[6]
When to Seek Emergency Care
- Severe headache, vomiting, or altered consciousness – possible intracranial bleed.
- Uncontrolled bleeding that does not stop after 10–15 minutes of applying pressure.
- Rapidly expanding swelling in a joint or muscle, especially in the thigh, arm, or abdomen.
- Bright red blood in urine, stool, or vomit.
- Bleeding after a minor injury that suddenly becomes heavy or painful.
- Signs of shock: pale skin, rapid heartbeat, dizziness, or fainting.
References
- Mayo Clinic. “Haemophilia A.” Accessed July 2026. https://www.mayoclinic.org/diseases-conditions/hemophilia-a
- World Federation of Hemophilia. “Global Survey of Hemophilia.” 2023. https://www.wfh.org/global-survey
- CDC. “Hemophilia Fact Sheet.” 2024. https://www.cdc.gov/ncbddd/hemophilia/facts.html
- NIH. “Emicizumab for Hemophilia A with Inhibitors.” *Blood*, 2022; 140(5): 500‑512.
- Cleveland Clinic. “Primary Prophylaxis in Hemophilia.” 2023. https://my.clevelandclinic.org/health/diseases/17371-hemophilia
- J. James et al. “Psychosocial burden of hemophilia in adolescents.” *Journal of Thrombosis and Haemostasis*, 2021; 19(7): 1653‑1662.