How Hemophilia B Is Diagnosed

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Hemophilia B is a type of blood-clotting disorder (hemophilia) that is caused by a deficiency in the blood-clotting protein factor IX (or factor 9).

There are three types of hemophilia. The two most common types, hemophilia A and hemophilia B, are similar in that they usually involve excessive bleeding or bruising after a minor injury, dental procedure, or surgery; bleeding from the gums or nose; or spontaneous bleeding in the joints, especially in the ankle, knee, and elbow.

If hemophilia is suspected, it's important to seek a diagnosis and treatment as soon as possible to avoid any complications from untreated bleeding episodes.

Many other conditions have similar symptoms as hemophilia B, therefore, it is imperative that your healthcare provider takes a detailed medical history, does a thorough physical examination, and orders specialized labs, imaging, and blood tests to make a prompt and accurate diagnosis.

This article will discuss the diagnostic process.

Factor IX

Md Saiful Islam Khan / iStock / Getty Images Plus


The first signs of hemophilia usually occur in childhood. Sometimes an infant will experience prolonged bleeding after getting a routine vaccination shot or vitamin K injection at birth. Or a parent may notice that a bruise is not going away after a minor fall or that a cut is slow to heal.

Parents who suspect their child may have hemophilia may check the child's body for any other signs of bruising or swelling and ask family members if they know of other relatives who experienced the same thing. 

Physical Examination

A healthcare provider will take a detailed history prior to performing a physical exam. They may start by asking you your age, gender identification, and the pronouns you use.

Next, they will ask about your symptoms, also known as your chief complaint. Taking a detailed history is essential to making an accurate diagnosis so your provider will also likely ask you about the following:

  • Birth history
  • Bleeding history, including type and location of bleeding, as well as any history of prolonged bleeding after minor injury or history of spontaneous bleeding. You may be referred to a hematologist (a doctor specializing in blood disorders), who may ask you about episodes of excessive bruising and/or bleeding with medical procedures such as immunizations.
  • Family history, especially any genetic conditions or history of prolonged bleeding in family members
  • Recent trauma or surgery
  • Immunization history

During the physical exam, your healthcare provider will look for bruising, pallor (sickly paleness), joint deformity, and limb/joint asymmetry. They may look for evidence of swelling like discolored areas of the skin and ask you if any areas of the body feel warm or painful. 

Next, the healthcare provider may palpate (feel by physical touch) for joint tenderness or swelling (joint effusion) in the elbow, wrist, knee, ankle, and neck, or muscle (most commonly the quadriceps, hamstrings, iliopsoas, biceps, and triceps).

Your healthcare provider may also move or ask you to move your limbs to assess range of motion (how far a body part can move or stretch) and pain with movement. Limited range of motion and signs of joint swelling may raise clinical suspicion for hemarthrosis, a common symptom of hemophilia B.  

Labs and Tests

Your healthcare provider will order numerous blood tests, including a complete blood count (CBC), coagulation tests to check the function of clotting factors, tests to assess bleeding times, and genetic testing, as necessary.

If hemophilia B is suspected based on symptoms, early blood work, and coagulation tests, a more specialized blood test to measure factor IX, called a factor IX (FIX) assay, may be ordered to measure levels of this specific blood-clotting protein.

The following FIX levels denote the severity of hemophilia B:

  • Mild: More than 5%–40% of normal in blood plasma. This often causes bleeding only after serious injury, trauma, or surgery. In many cases, people with mild hemophilia are unaware that they have the condition and only find out after an injury, surgery, or tooth extraction results in prolonged bleeding. Women with mild hemophilia often experience menorrhagia, heavy menstrual periods, and may hemorrhage after childbirth.
  • Moderate: Around 1%–5% of normal levels. Those with this type of hemophilia B may have bleeding episodes after injuries or have spontaneous bleeding episodes, but even this small amount of FIX can help stave off life-threatening bleeding episodes.
  • Severe: Less than 1% of normal levels in blood plasma. People with severe hemophilia B experience bleeding following an injury and may have frequent spontaneous bleeding episodes, often into their joints and muscles

Once an individual is diagnosed with hemophilia B, genetic testing to look for the specific mutation in the F9 gene responsible for your hemophilia B may also be performed. 


Although imaging is not needed to make a diagnosis of hemophilia B, it is helpful in the early detection and management of symptoms. The hallmark symptom of hemophilia B is hemorrhage, particularly into joints and/or soft tissue, also known as hemarthrosis.

If left untreated, hemarthrosis can lead to contracture (stiffening of joints and muscle) and limited range of motion. The following imaging modalities may be used to uncover hidden bleeding in those with hemophilia B:

  • Musculoskeletal ultrasonography (MSKUS): Ultrasound is a fast, efficient, safe, and cost-effective imaging type in early detection and management of hemarthrosis. It can detect bleeding in joints, synovial hypertrophy (increase in size of the membrane around a joint, indicating inflammation), cartilage damage, and muscle bruising (hematoma).
  • X-ray: X-rays can identify irregularity of the joint space, joint effusion, and epiphyseal (end of a long bone) overgrowth, but it is an unreliable way to evaluate damage to the cartilage or soft tissues.
  • Computed tomography (CT) scan: A computer compiles multiple X-rays to create a three-dimensional image of an area of the body. Non-contrast (without the use of dye) head CT is used to assess the presence of a brain bleed (intracranial bleed).
  • Magnetic resonance imaging (MRI): An MRI, which uses strong magnetic fields and radio waves to create detailed images of internal structures, is the best way to evaluate soft tissue and cartilage when assessing for issues like joint swelling (hemarthrosis), internal bleeding, or muscle bruising.

Differential Diagnosis

Many diseases that present similarly to bleeding episodes should be excluded before a diagnosis of hemophilia B is reached. These include:

  • Other blood-clotting factor defects: This includes hemophilia A (deficiency in factor VIII) and hemophilia C (deficiency in factor XI).
  • Von Willebrand factor (VWF) deficiency: VWF factor deficiency is the most common type of bleeding disorder. Insufficient levels or nonworking VWF results in prolonged bleeding because the body is unable to form a platelet plug (clot) after injury. VWF deficiency differs from hemophilia B in several ways, including the presence of a normal or increased clotting factor prothrombin time (PTT). Symptoms of von Willebrand disease are usually milder than those of true hemophilia.  
  • Platelet disorders: These can cause prolonged bleeding such as immune thrombocytopenia, thrombotic thrombocytopenia, and hemolytic uremic syndrome.
  • Disseminated intravascular coagulation (DIC): DIC is abnormal blood clotting throughout the blood vessels from life-threatening conditions such as sepsis, trauma, obstetric (pregnancy) complications, acute pancreatitis, acute myelogenous leukemia, and adverse reactions from blood transfusions.
  • Vitamin K deficiency: This condition is usually identified in infancy.
  • Scurvy or vitamin C deficiency: Deficiencies in vitamin C can lead to poor wound healing and a host of other symptoms including swollen gums and hemarthrosis.
  • Ehlers-Danlos syndrome: This is a defect in collagen synthesis, which results in fragile tissue, skin that is easily stretched and bruised, and hypermobile joints (moving beyond normal range).
  • Fabry disease: This rare genetic condition can lead to spontaneous bleeds. Bleeding normally occurs in mucosal areas, like the gums, as opposed to musculoskeletal areas in those with hemophilia B. 
  • Child abuse: Frequent bruises from physical abuse can be misidentified and confused with easy bruising from hemophilia. Inconsistencies in the history of how the trauma occurred, malnourishment, red bloodshot eyes, and wounds in different stages of healing raises the likelihood that child abuse is the cause of bleeding. If suspected, physical abuse should be reported to the proper authorities for further investigation.


Hemophilia B may be suspected based on an individual's symptoms, bleeding history, and family history. Normal blood work and coagulation tests do not rule out the diagnosis.

Typically, a specialized blood test for factor IX levels, called a factor IX assay, must be done to confirm a diagnosis of hemophilia B and determine the severity of the condition. Genetic testing that can detect mutations on the F9 gene may also be done. 

A Word From Verywell

A diagnosis of hemophilia B can be jarring at first, but there may be comfort in knowing the exact cause of your bleeding episodes. Knowing the cause means you can begin addressing your symptoms. 

Hemophilia B may affect your life by creating mobility difficulties, unexpected bleeding, pain, and uncertainty in daily activities. So, it's important that you learn how to recognize signs of bleeding and be prepared for bleeding episodes.

If you or your child does receive a hemophilia B diagnosis, be sure to seek out the nearest certified hemophilia treatment center (HTC). The specialists there can help you chart the best course of treatment and management, which can empower you to live with less fear.

It's also important to ask for support from trusted family members and friends, who may be able to help in a time of need. Hemophilia can affect your mental health, so you may also find value in connecting with local, national and international support organizations.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Zimmerman B, Valentino LA. Hemophilia: in reviewPediatr Rev. 2013;34(7):289-295. doi:10.1542/pir.34-7-289

  2. National Organization for Rare Disorders. Hemophilia B.

  3. Zaiden, RA. Hemophilia B differential diagnoses. Medscape. Updated October 2, 2020. 

By Shamard Charles, MD, MPH
Shamard Charles, MD, MPH is a public health physician and journalist. He has held positions with major news networks like NBC reporting on health policy, public health initiatives, diversity in medicine, and new developments in health care research and medical treatments.