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Overview

What Is Hemophilia?

Hemophilia is an inherited bleeding disorder in which the blood does not clot normally. Hemophilia A involves low or missing clotting factor VIII, while hemophilia B involves low or missing factor IX. Hemophilia most often affects males because the gene changes are usually carried on the X chromosome, while females may be carriers and may also have bleeding symptoms. This hemophilia definition explains why bleeding can last longer than expected after an injury or procedure.

HEMOPHILIA A

Caused by low or absent clotting factor VIII. It is more common than hemophilia B, but its symptoms can be similar.

HEMOPHILIA B

Caused by low or absent clotting factor IX. It is less common than hemophilia A and can also cause prolonged bleeding and bleeding into joints or muscles.

Symptoms

Hemophilia Symptoms

  • Bleeding that lasts longer than expected after cuts, injuries, dental work, or surgery (prolonged bleeding).
  • Bruising easily or developing large bruises after minor bumps (easy bruising).
  • Frequent or difficult-to-stop nosebleeds (epistaxis).
  • Blood in the urine (hematuria).
  • Blood in the stool or black, tarry stools (gastrointestinal bleeding).
  • Painful swelling or reduced movement from bleeding into a joint (hemarthrosis).
  • Pain, swelling, or tightness from bleeding into a muscle or soft tissue (muscle hematoma).

Severe hemophilia may cause bleeding without an obvious injury, while mild hemophilia may become apparent only after surgery, dental work, or a significant injury. Infants may develop symptoms as they become more mobile and begin crawling or walking. The type and severity of hemophilia depend largely on the person’s clotting-factor level.

Causes

Causes of Hemophilia

Changes in the F8 gene cause hemophilia A by reducing clotting factor VIII. Changes in the F9 gene cause hemophilia B by reducing clotting factor IX. These clotting factors are needed to build a stable blood clot, so low activity can lead to prolonged or recurrent bleeding. This is the underlying cause of hemophilia A and B disease.

Family situationPotential inheritance implication
Affected maleA male with the relevant X-linked gene variant can pass it to all daughters, but not to sons.
Carrier femaleA female with an F8 or F9 variant may pass it to sons, who may have hemophilia, and to daughters, who may be carriers or have symptoms.
Affected femaleAn affected female is uncommon but possible, depending on the gene variants inherited and the level of clotting-factor activity.
Family with no known historyA new genetic change can occur, so hemophilia may appear even when no relative is known to have the disorder.

Risk Factors

Hemophilia Risk Factors

  • A family history of hemophilia or another inherited bleeding disorder.
  • Carrying an F8 or F9 gene variant.
  • Being male and inheriting an X-linked F8 or F9 gene variant.
  • Having personal or family bleeding patterns that suggest an unrecognized inherited bleeding disorder.

Complications

Hemophilia Complications

  • Joint damage caused by repeated bleeding into the joints.
  • Muscle or soft-tissue bleeding that causes swelling, pain, or pressure on nearby structures.
  • Anemia from repeated or severe blood loss.
  • Intracranial bleeding, or bleeding inside the skull.
  • Gastrointestinal or urinary tract bleeding.
  • Inhibitors, which are antibodies that reduce the effect of replacement clotting factor.

Repeated joint bleeds can cause chronic pain, stiffness, and reduced mobility. Bleeding in the head, throat, abdomen, or another critical area can be life-threatening and needs urgent medical attention. Specialist monitoring helps identify complications and adjust treatment when needed.

Diagnosis

How Hemophilia Is Diagnosed

Clinicians assess personal and family bleeding history, examine for bruising or swollen joints, and consider what prompted testing. Unusual bleeding after surgery or dental work, recurrent joint swelling, or unexplained prolonged bleeding may lead to testing. A family history can also support evaluation, even when symptoms are mild.

  • A complete blood count checks blood-cell levels and may help assess blood loss or anemia.
  • Screening clotting tests, including activated partial thromboplastin time (aPTT), assess how quickly blood forms a clot.
  • Factor VIII and factor IX activity assays identify hemophilia A or B and measure clotting-factor activity.
  • Inhibitor testing looks for antibodies when replacement treatment is ineffective or an inhibitor-related complication is suspected.

Genetic testing may identify the causative variant and support family counseling. Factor activity levels help classify hemophilia as mild, moderate, or severe, although results should be interpreted by an experienced clinician.

Treatment & Management

Hemophilia Treatment and Management

Clotting-Factor Replacement and Prevention

Clotting-factor replacement is the foundation of hemophilia treatment. Intravenous factor VIII is used for hemophilia A, and factor IX is used for hemophilia B. Treatment may be given on demand for active bleeding or regularly as prophylaxis to prevent bleeds and protect the joints. Desmopressin may help selected people with mild hemophilia A, and prescribed antifibrinolytic medicines may be useful for appropriate mucosal bleeding.

Non-Factor Treatment and Daily Planning

Emicizumab is a non-factor preventive medicine for eligible people with hemophilia A. If inhibitors develop, bypassing agents or other specialist-directed approaches may be needed. Long-term care can include a hematology team, physical therapy, dental care, recommended vaccinations, medical identification, and an individualized emergency plan. Gene therapy may be considered only as a specialist-evaluated option for eligible adults. The best treatment for hemophilia is individualized according to the type, severity, bleeding pattern, and treatment response.

Outlook and Prognosis

Outlook and Prognosis for Hemophilia

Hemophilia is a lifelong condition rather than a short-term illness, but many people can maintain active lives with individualized prophylaxis, rapid treatment of bleeds, and regular specialist follow-up. Early attention to joint symptoms and consistent preventive care can help protect long-term function.

WITH PREVENTIVE CARE

Consistent treatment can reduce bleeding, help protect joint health, and support participation in school, work, exercise, and daily activities. A comprehensive hemophilia treatment center can coordinate ongoing care.

WITHOUT ADEQUATE CARE

Repeated untreated bleeding can damage joints, cause chronic pain and stiffness, and limit mobility or participation in daily life. Prompt treatment and specialist follow-up are important for reducing these risks.

When Should You See a Doctor

When Should You See a Doctor for Hemophilia?

CONTACT A CLINICIAN

Arrange Prompt Medical Evaluation

Contact a clinician if hemophilia is suspected, bleeding is unusual or persistent, bruising keeps recurring without a clear cause, or a joint becomes swollen and painful. Seek advice if bleeding does not respond to the prescribed treatment plan.

GET EMERGENCY HELP

Recognize Emergency Bleeding

Seek emergency care for a head injury, severe headache, confusion, weakness, neck or throat swelling, trouble breathing or swallowing, severe abdominal pain, vomiting blood, black stools, or heavy bleeding. Tell emergency responders that the person has hemophilia.

Ask about evaluation at or referral to a comprehensive hemophilia treatment center. Established hemophilia organizations, including the Hemophilia Federation of America, and public-health resources can provide education and support, but they are not substitutes for urgent medical care.

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