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Blood disorders

Haemophilia, when blood can't clot, explained

What haemophilia A and B are, why it mostly affects boys, how factor replacement therapy works, and why it is nothing like an ordinary blood transfusion.

Haemophilia is the opposite problem from most blood disorders: not too little blood, but blood that cannot stop flowing. A missing clotting protein turns every knock, dental procedure and internal bruise into a medical event. This page explains the condition and why its treatment runs through the blood system in a completely different way from transfusion.

The clotting cascade, missing one gear

When a vessel breaks, a cascade of proteins hands off the clotting job like a relay baton, ending in a proper plug. In haemophilia A, factor VIII is missing or faulty. In haemophilia B (Christmas disease), it’s factor IX. The cascade stalls at that gear: the initial plug forms, but the strong, stable clot doesn’t.

Why it’s mostly boys

The genes live on the X chromosome. Boys have one X (a single faulty copy means the disease. Girls have two) one faulty copy usually makes them carriers, healthy but able to pass it on. (There is a famous royal lineage: Queen Victoria was a carrier, and the disease threaded through European royal houses, which is why haemophilia earned the nickname “the royal disease.”) Girls can have haemophilia in rarer genetic situations; the centre and a haematologist handle those cases.

What bleeds look like

  • Joints (haemarthroses), the signature: knees, elbows, ankles swelling painfully from internal bleeding, repeatedly, from childhood.
  • Muscles, deep bleeds that can compress nerves.
  • Dangerous ones, head injury, neck, abdominal bleeds: emergencies even from minor knocks.
  • Dental work and circumcision, classic first presentations in undiagnosed boys.

Treatment: factor replacement, not an ordinary transfusion

The modern treatment is factor replacement therapy: infusions of the missing factor (VIII or IX concentrates). Some patients infuse on demand when bleeding starts; many children now receive prophylaxis, scheduled infusions several times a week to prevent bleeds before they happen. This is why haemophilia care is completely different from ordinary transfusion: the patient isn’t missing blood volume, they’re missing one specific protein, and the therapy delivers that protein, often derived from plasma or produced recombinantly.

Plasma-derived factors are one reason plasma donations matter even in the era of recombinant products. Where plasma comes from →

Living with haemophilia today

With factor therapy, protective habits and a haematology team, boys with haemophilia in India play, study, work and grow up, the treatment just has to be available when needed. That availability depends on diagnosis, affordable factor supply, and the blood system’s plasma base.

The family angle

Carriers should know their status before planning families (the genetics counselling route). And every family living with haemophilia knows the local donor-list question: factor therapy first, transfusion support sometimes, both start at the register. Register →

Medically significant topic: educational, pending formal medical review. Diagnosis and treatment belong with a haematologist.

Explore

Blood disorders overview → · what is blood? → · how blood clots: platelets →

People also ask

What is haemophilia?

An inherited clotting disorder, usually factor VIII (haemophilia A) or factor IX (haemophilia B) is missing or faulty. Bleeding continues far longer than normal, including internal bleeding into joints and muscles.

Why does haemophilia mostly affect boys?

The genes sit on the X chromosome. Boys (XY) who inherit one faulty X have the disease; girls (XX) who inherit one faulty X are usually carriers.

How is haemophilia treated?

By replacing the missing factor, infusions of factor VIII or IX concentrates, given on demand for bleeds or regularly as prophylaxis. It is not an ordinary blood transfusion.

About this article

Written by Assam Blood Donor team. Medical review: pending, content follows published national (NBTC/NACO) guidance and is for general education, not personal medical advice. Last updated 28 Aug 2026.

Sources: National Blood Transfusion Council (NBTC) guidance · standard haematology references · National Health Mission resources

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