Hemophilia B in Primary Care: 5 Key Questions About Recognition, Diagnosis, and Management

• Severe: less than 1% of normal factor IX activity
• Moderate: 1% to 5% of normal factor IX activity
• Mild: greater than 5% but less than 40% of normal factor IX activity²˒³

The bleeding phenotype does not always correspond precisely with the measured factor level, so the patient’s personal and family bleeding histories remain important.²˒⁴

Symptoms may include prolonged bleeding after injury, surgery, dental work, childbirth, or circumcision. There may also be easy bruising, large hematomas, and blood in the urine or stool. Patients with more severe disease may experience spontaneous bleeding into joints or muscles. Joint bleeding commonly affects the knees, ankles, and elbows and may cause pain, warmth, swelling, restricted movement, and progressive joint damage when episodes recur.¹˒²

Patients and caregivers should seek urgent evaluation for significant head trauma; suspected bleeding in the head, neck, throat, abdomen, or back; rapidly expanding muscle swelling; uncontrolled bleeding; or neurologic symptoms, such as severe headache, vomiting, confusion, weakness, or loss of consciousness. For suspected life- or limb-threatening bleeding, hemostatic treatment should be administered promptly in accordance with the patient’s established emergency plan. It should not be delayed while awaiting imaging or laboratory confirmation.⁴

• Marstacimab (Hympavzi): Routine prophylaxis in adults and children aged 6 years or older with hemophilia B, with or without factor IX inhibitors.⁵
• Concizumab (Alhemo): Routine prophylaxis in adults and adolescents aged 12 years or older with hemophilia B, with or without factor IX inhibitors.⁶
• Fitusiran (Qfitlia): Routine prophylaxis in adults and adolescents aged 12 years or older with hemophilia B, with or without factor IX inhibitors.⁷

These therapies have different mechanisms, dosing schedules, monitoring requirements, effects on laboratory testing, and risks, including thromboembolic complications. They should be prescribed and managed by clinicians experienced in hemophilia care.⁵⁻⁷

Adeno-associated virus vector–based gene therapy may be considered for certain adults with hemophilia B. Etranacogene dezaparvovec-drlb (Hemgenix) is indicated for adults who currently use factor IX prophylaxis, have a current or historical life-threatening hemorrhage, or have experienced repeated serious spontaneous bleeding episodes.⁸

Before gene therapy, patients require evaluation for factor IX inhibitors and liver-related risks. Etranacogene dezaparvovec-drlb should not be administered to patients with an active factor IX inhibitor, and patients require long-term monitoring of factor IX activity and liver health after treatment.⁸ Gene therapy is intended to enable liver cells to produce factor IX after a single intravenous administration, potentially reducing bleeding and the need for routine factor prophylaxis.

Primary care physicians should avoid describing gene therapy as a definitive cure. Treatment response and durability vary, and patients may still require hemostatic therapy for surgery, trauma, or breakthrough bleeding. With access to prophylaxis, comprehensive specialist care, and prompt treatment of bleeding, many patients can maintain active lives. Chronic joint disease, pain, inhibitors, treatment burden, and other comorbidities may nevertheless continue to affect long-term health and quality of life.²˒⁴˒⁸

Primary care physicians should also recognize that women and girls can be diagnosed with hemophilia B. Heavy menstrual bleeding, postpartum hemorrhage, excessive procedural bleeding, easy bruising, or other bleeding symptoms warrant evaluation, even when a patient has previously been described only as an F9 variant carrier. Factor IX levels do not physiologically increase during pregnancy as factor VIII levels can, so pregnancy does not provide the same potential increase in clotting factor activity for women with hemophilia B.³

Bruising or mucosal bleeding alone is not specific to hemophilia. Platelet disorders, von Willebrand disease, medication effects, liver disease, acquired coagulation disorders, and nonaccidental trauma may produce overlapping manifestations. Deep-muscle bleeding, hemarthrosis, and delayed or prolonged bleeding after procedures are particularly suggestive of a coagulation-factor deficiency. ²

Diagnosis requires a specific factor IX activity assay. Factor VIII activity testing and testing for von Willebrand disease may also be appropriate, as hemophilia A, hemophilia B, and von Willebrand disease can have overlapping presentations.¹˒² If the activated partial thromboplastin time is prolonged, the laboratory or hematologist may use a mixing study to help distinguish a factor deficiency from an inhibitor.

Patients with low factor IX activity should be referred to a hematologist or hemophilia treatment center for confirmation, severity classification, inhibitor testing, genetic evaluation, and development of an individualized treatment plan. Genetic testing can identify the causative F9 variant, clarify inheritance, and support testing and counseling for relatives.¹⁻³

Primary care physicians should not delay hematology consultation when a patient has active, clinically significant bleeding. Factor assays and other coagulation tests may also be difficult to interpret after administration of factor replacement or certain nonfactor therapies, making communication with the patient’s hemophilia treatment center essential.⁴⁻⁷

Dental work, surgery, endoscopy with possible intervention, joint injections, and other invasive procedures require advance coordination with the hemophilia treatment center. The hemostatic plan may include factor IX replacement, antifibrinolytic therapy, adjustment or interruption of prophylaxis, and postprocedural monitoring. The appropriate strategy depends on the procedure, the factor's baseline activity, inhibitor status, and current treatment.⁴⁻⁷

Medication review is an important responsibility in primary care. Aspirin and nonselective NSAIDs may increase bleeding risk and should generally be avoided unless their clinical benefit has been reviewed with hematology. Pain management should be individualized, particularly for patients with chronic pain or hemophilic arthropathy. Acetaminophen is often used for uncomplicated pain when clinically appropriate.

Anticoagulant and antiplatelet therapies should not be initiated or discontinued without an individualized assessment by hematology and the clinician managing the cardiovascular indication. Similarly, intramuscular injections, arterial punctures, and other potentially traumatic procedures should be avoided when a safer alternative exists or planned according to the patient’s hematology recommendations.⁴

Routine preventive care remains essential. Vaccines should be administered by the recommended route rather than routinely changing an intramuscular vaccine to a subcutaneous route. For an intramuscular vaccine, clinicians should follow the patient’s hematology plan, consider timing vaccination after hemostatic therapy when applicable, use a fine-gauge needle, and apply firm pressure without rubbing for at least 2 minutes.¹⁰

Primary care physicians should continue to provide age-appropriate vaccinations, cancer screening, cardiovascular risk reduction, mental health screening, and management of obesity, hypertension, diabetes, and other chronic conditions. They can also identify reduced mobility, chronic pain, joint deterioration, treatment nonadherence, depression, school or workplace challenges, and caregiver strain.

Referral to an accredited hemophilia treatment center supports coordinated access to hematology, nursing, physical therapy, dentistry, social work, genetic counseling, and other specialized services.¹˒⁴ Primary care physicians remain important partners in medication reconciliation, preventive care, recognition of complications, and communication across the multidisciplinary team.