Hemophilia

What is hemophilia?

Hemophilia is an inherited bleeding disorder in which the blood does not clot properly. When a person without hemophilia is injured, the body launches a chain reaction of proteins called clotting factors that work together to form a stable clot and stop the bleeding. In hemophilia, one of these clotting factors is missing or present at abnormally low levels, so bleeding lasts longer than it should. Understanding what is hemophilia begins with this simple idea: it is not that people with the condition bleed faster, but that they bleed longer, and sometimes internally in ways that are not immediately visible.

There are two main types. Hemophilia A, the more common form, is caused by a shortage of clotting factor VIII (factor eight). Hemophilia B is caused by a shortage of clotting factor IX (factor nine). Both types produce similar symptoms, and doctors distinguish between them with laboratory tests. Hemophilia is usually present from birth, and in most cases it affects males, because of the way the responsible gene is inherited. Females can also carry the gene and, in some cases, may experience bleeding symptoms themselves.

Hemophilia ranges from mild to severe depending on how much clotting factor the body produces. People with severe hemophilia may bleed spontaneously into joints and muscles, while people with mild hemophilia may only notice a problem after surgery, dental work, or a significant injury. The condition is lifelong, but with modern hemophilia treatment, many people manage it successfully and lead full, active lives.

Symptoms of hemophilia

Hemophilia symptoms vary widely depending on the severity of the clotting factor deficiency. Common signs include:

• Prolonged bleeding after cuts, injuries, surgery, or dental procedures
• Large or deep bruises, sometimes from minor bumps or with no clear cause
• Joint bleeding (hemarthrosis) — pain, swelling, warmth, or tightness in a joint, most often the knees, elbows, or ankles
• Muscle bleeds causing swelling, pain, or stiffness in an arm or leg
• Frequent or hard-to-stop nosebleeds
• Blood in the urine or stool, which may signal internal bleeding
• Prolonged bleeding after vaccinations or other injections
• In infants: unusual bleeding after circumcision, or unexplained irritability that may reflect internal bleeding

The pattern of symptoms usually reflects the severity of the condition. In severe hemophilia, where clotting factor levels are very low, bleeding can occur spontaneously — that is, without any injury — often into joints and muscles. Repeated bleeding into the same joint over time can damage the cartilage and lead to chronic pain and reduced movement, a complication doctors call hemophilic arthropathy. In moderate hemophilia, bleeding typically follows injuries, though occasional spontaneous bleeds can happen. In mild hemophilia, symptoms may not appear until adulthood, often discovered only after an operation, a tooth extraction, or a serious accident causes unexpected prolonged bleeding.

The most dangerous form of bleeding in hemophilia is bleeding inside the skull (intracranial hemorrhage). Warning signs may include a severe or persistent headache, repeated vomiting, sleepiness, confusion, sudden weakness, vision changes, or seizures. This is a medical emergency at any severity level of hemophilia.

Causes and risk factors

Hemophilia causes are genetic in the vast majority of cases. The genes that instruct the body to make clotting factors VIII and IX are located on the X chromosome, one of the two chromosomes that determine biological sex. Males have one X chromosome and one Y chromosome; females have two X chromosomes. Because males have only one X chromosome, a single altered gene on that chromosome is enough to cause hemophilia. Females who carry an altered gene on one X chromosome usually have a second, working copy on their other X chromosome, so they often have milder symptoms or none at all — but they can pass the gene to their children. This inheritance pattern explains why hemophilia occurs mainly in males.

Key points about causes and risk:

• Family history is the strongest risk factor. If hemophilia runs in a family, sons of carrier mothers have a chance of inheriting the condition, and daughters have a chance of being carriers.
• New (spontaneous) gene changes account for a meaningful share of cases. In many families, a child with hemophilia is the first person known to have the condition, because the gene alteration occurred for the first time in that child or a recent generation.
• Acquired hemophilia is a rare, non-inherited form that can develop later in life when the immune system mistakenly produces antibodies that attack the body’s own clotting factor, most often factor VIII. It can be associated with pregnancy, autoimmune conditions, certain cancers, or may have no identifiable trigger.

Hemophilia is not contagious, and it is not caused by anything a parent did during pregnancy. Diet, lifestyle, and environment do not cause the inherited forms of the condition.

Diagnosis

Hemophilia diagnosis relies on blood tests rather than imaging. Doctors may suspect the condition because of a family history, unusual bruising or bleeding in a child, or unexpectedly prolonged bleeding after surgery or an injury. The diagnostic process typically includes:

• Medical and family history — a careful review of bleeding episodes and any relatives with known bleeding disorders.
• Screening clotting tests — a test called the activated partial thromboplastin time (aPTT) measures how long part of the clotting process takes. In hemophilia, this time is usually prolonged, while other clotting screens, such as the prothrombin time (PT) and platelet count, are often normal.
• Clotting factor assays — these are the confirmatory tests. They measure the exact activity level of factor VIII and factor IX in the blood. Low factor VIII confirms hemophilia A; low factor IX confirms hemophilia B. The measured level also defines severity: doctors generally classify hemophilia as severe, moderate, or mild based on how much factor activity remains compared with normal.
• Genetic testing — identifying the specific gene alteration can help confirm the diagnosis, identify carriers in the family, and support family planning decisions. It may also give some information about the likelihood of certain complications.

In families with known hemophilia, testing can be performed on newborns shortly after birth. Prenatal testing is possible in some situations and is usually discussed with a genetic counselor. Doctors may also test for inhibitors — antibodies that the immune system sometimes develops against replacement clotting factor — because inhibitors change how the condition is treated. Imaging tests such as ultrasound or magnetic resonance imaging (MRI) are not used to diagnose hemophilia itself, but they may be used to assess bleeding into joints or muscles and to monitor joint health over time.

Treatment options for hemophilia

There is currently no routine cure for hemophilia, but treatment has advanced considerably and most bleeding can be prevented or controlled. The right approach depends on the type of hemophilia, its severity, whether inhibitors are present, and the individual’s age and lifestyle. Care is typically coordinated by a hematologist — a doctor who specializes in blood disorders — often within a specialized hematology department. An overview of how the condition is evaluated and managed is available on the hemophilia treatment page.

Clotting factor replacement therapy

The cornerstone of hemophilia treatment is replacing the missing clotting factor. Concentrated factor VIII or factor IX is given by infusion into a vein. This can be done in two ways:

• Prophylaxis (preventive treatment) — regular, scheduled infusions to keep factor levels high enough to prevent spontaneous bleeds. This is the standard of care for severe hemophilia, particularly in children, because it helps protect joints from long-term damage.
• On-demand (episodic) treatment — infusions given to stop bleeding when it occurs, sometimes used for milder forms of the condition.

Modern factor concentrates are either made from carefully screened and treated donated plasma or produced in the laboratory using recombinant technology, which does not use human blood. Extended half-life products, which stay active in the body longer, may allow fewer infusions. Many families are trained to give infusions at home, which makes prompt treatment of bleeds much easier.

Non-factor and other medications

• Emicizumab — an antibody-based medicine given as an injection under the skin that mimics the function of factor VIII. It is used for preventive treatment in hemophilia A, including in people with inhibitors.
• Desmopressin (DDAVP) — a hormone-like medicine that can temporarily raise factor VIII levels in some people with mild hemophilia A. It is not effective for hemophilia B or severe hemophilia A.
• Antifibrinolytic medicines, such as tranexamic acid — these help stabilize clots once they form and are often used for mouth bleeds, nosebleeds, or dental procedures.
• Bypassing agents — special products used to control bleeding in people who have developed inhibitors against standard factor concentrates.

Treatment of inhibitors

Some people, more often those with severe hemophilia A, develop inhibitors that make standard factor replacement less effective. Doctors may recommend immune tolerance induction — a program of frequent factor infusions over months designed to teach the immune system to accept the factor — or use bypassing agents and non-factor therapies to manage bleeding.

Gene therapy

Gene therapy aims to give the body a working copy of the gene for the missing clotting factor, allowing it to produce factor on its own. Gene therapies have been approved in some countries for certain adults with hemophilia A or B. This is a developing field: not everyone is eligible, long-term durability is still being studied, and careful discussion with a specialist is essential before considering it.

Supportive care, procedures, and surgery

Physical therapy plays an important role in maintaining joint strength and mobility, especially after joint bleeds. When repeated bleeding has already caused significant joint damage, orthopedic procedures — from removal of the inflamed joint lining (synovectomy) to joint replacement surgery in selected adults — may be considered. Any surgery or dental procedure in a person with hemophilia requires careful planning with the hematology team so that factor levels are managed before, during, and after the intervention. Watchful waiting alone is not appropriate for active bleeding, but people with very mild hemophilia may need treatment only around procedures or injuries, under specialist guidance.

Living with hemophilia and outlook

The outlook for people with hemophilia has improved dramatically over recent decades. With access to modern preventive treatment, many people with hemophilia can attend school and work normally, exercise, travel, and have families. Life expectancy for people with well-managed hemophilia in countries with good access to care approaches that of the general population, although outcomes vary and depend on severity, access to treatment, and complications such as inhibitors or established joint damage.

Day-to-day life with hemophilia often involves:

• Following the prescribed treatment plan, including regular prophylactic infusions or injections where recommended.
• Staying physically active — regular, low-impact exercise such as swimming, walking, or cycling strengthens muscles that protect joints. High-contact sports are generally discouraged; your care team can advise on safe activities.
• Protecting the joints and teeth — good dental hygiene reduces the need for dental procedures that can cause bleeding.
• Avoiding certain medicines — aspirin and most nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, can increase bleeding risk and should generally be avoided unless a doctor approves them. Always check before taking new medicines or supplements.
• Wearing medical identification, such as a bracelet, so that emergency staff know about the condition.
• Regular follow-up at a specialized center for factor level monitoring, inhibitor screening, and joint assessments.

Living with a chronic condition can also affect mood and family life. Genetic counseling can help families understand inheritance and options for future pregnancies, and psychological support or patient organizations may help with the emotional side of long-term management. No treatment plan can guarantee that bleeds will never occur, but consistent care greatly reduces their frequency and long-term consequences in many cases.

Frequently asked questions

What is hemophilia in simple terms?

Hemophilia is an inherited condition in which the blood is missing enough of one of its clotting factors — the proteins that stop bleeding. As a result, bleeding after injuries lasts longer than normal, and in severe cases bleeding can start inside joints or muscles without any injury. It mainly affects males and is usually diagnosed with blood tests that measure clotting factor levels.

Can hemophilia be cured?

At present, there is no routine cure for hemophilia. Standard treatment replaces or compensates for the missing clotting factor to prevent and control bleeding. Gene therapy, which aims to enable the body to make its own clotting factor, has been approved in some countries for certain adults, but it is not suitable for everyone and its long-term results are still being studied. For most people, hemophilia is a lifelong condition that can be managed effectively with ongoing specialist care.

How serious is hemophilia?

Seriousness depends largely on how low the clotting factor level is. Mild hemophilia may cause problems only after surgery or major injuries, while severe hemophilia can cause spontaneous bleeding into joints, muscles, and — rarely but dangerously — the brain. Untreated, repeated joint bleeds can cause lasting joint damage. With modern preventive treatment, however, many people with even severe hemophilia avoid most bleeds and maintain a good quality of life.

What are the first signs of hemophilia in a baby or child?

In infants, early hemophilia symptoms may include prolonged bleeding after circumcision or blood draws, unusual bruising once the child starts to crawl or walk, and swelling or soreness in joints. Some babies show few signs until they become mobile. In families with a known history of hemophilia, doctors often test newborns soon after birth. If a child bruises very easily or bleeds longer than expected, a doctor can arrange simple blood tests to check clotting.

Can females have hemophilia?

Yes, although it is much less common. Females who carry one altered gene are called carriers, and some carriers have reduced factor levels and experience symptoms such as heavy menstrual periods, easy bruising, or prolonged bleeding after surgery or childbirth. In rare cases, a female inherits altered genes on both X chromosomes and has hemophilia in the same way males do. Carriers who have symptoms benefit from evaluation by a hematologist.

Is hemophilia treatment lifelong?

For most people, yes. Inherited hemophilia does not go away, so treatment — whether regular preventive infusions, injections of non-factor medicines, or on-demand treatment of bleeds — continues throughout life. Treatment plans are adjusted over time as needs change, for example around surgery, sports, or pregnancy planning in carriers. Emerging therapies may reduce the treatment burden for some people in the future, but ongoing specialist follow-up remains important.

Can people with hemophilia play sports?

In many cases, yes — regular exercise is actually encouraged because strong muscles help protect joints. Low-impact activities such as swimming, walking, and cycling are generally considered safer choices. High-contact sports such as boxing, rugby, or American football carry a higher risk of dangerous bleeding and are usually discouraged. The right activities depend on the severity of the condition and the treatment plan, so decisions are best made together with the care team.

When to see a doctor

Anyone with unexplained easy bruising, prolonged bleeding, or a family history of bleeding disorders should discuss testing with a doctor. People already diagnosed with hemophilia should follow the emergency plan agreed with their care team. Seek urgent medical care if you or your child experiences any of the following red-flag signs:

• Signs of bleeding in the head: severe or worsening headache, repeated vomiting, unusual drowsiness, confusion, slurred speech, sudden weakness, vision changes, or seizures — treat this as an emergency.
• Any significant head injury, even if there are no symptoms yet.
• Neck or throat swelling, difficulty swallowing, or trouble breathing, which may indicate bleeding that can block the airway.
• Bleeding that will not stop despite pressure or usual home treatment.
• Sudden joint or muscle pain, swelling, warmth, or tightness, which may signal an internal bleed — early treatment protects the joint.
• Severe abdominal pain, blood in vomit, urine, or stool, or black, tarry stools.
• Signs of serious blood loss: pale skin, rapid heartbeat, dizziness, or fainting.
• Numbness, tingling, or weakness in a limb after a muscle bleed, which can indicate pressure on nerves.

For people with severe hemophilia, prompt factor replacement at the first sign of a bleed — often before swelling or bruising is visible — leads to better outcomes in many cases. When in doubt, it is safer to treat and seek medical advice than to wait.