A Study to Evaluate the Real-world Effectiveness and Usage of Alprolix in Patients With Haemophilia B in France

Inclusion Criteria: * Have a diagnosis of haemophilia B and been treated previously with factor IX Product * Have started Alprolix treatment prior to enrolment visit, or at enrolment prescribed treatment with Alprolix, regardless of participation in the study * Signed and dated informed consent provided by the patient, or the patient's legally acceptable representative for patients under the legal age, before any study-related activities are undertaken. Assent should be obtained from paediatric patients according to local regulations Exclusion Criteria: * Participation in an investigational medicinal product trial at enrolment visit