Severe haemophilia A and B (SHA, SHB) are inherited bleeding disorders affecting male patients and are characterised by low levels of circulating clotting factors VIII and IX respectively. Clinically low levels present with multiple recurrent bleeds into joints and muscle from the first couple of years of life. In addition patients may present with spontaneous and potentially fatal bleeding into any organ. The mainstay of treatment is replacement with the missing factor in the form of intravenous injections of factor VIII and IX. Clotting factors can be given to treat a bleed or can be given to prevent a bleed, and the latter is termed prophylaxis. Regular prophylaxis is the current standard of care and aims to decrease spontaneous bleeding events and resulting joint damage, and this requires patients to self-infuse factor into their veins two to four times week. Patient's compliance with prescribed regimen and recommendations has a significant influence on outcomes.

Advances in biomolecular and protein engineering have extended the duration of the effect of clotting factor VIII and IX through multiple mechanisms. This extension of the duration of the effect presents the clinician and patients with opportunities to tailor the treatment to their particular needs, circumstances and body other characteristics. It has been suggested that decreasing the frequency of infusions will improve adherence and thus contribute to improved outcomes.

In rare disorders, it is an accepted fact that post-marketing studies are crucial to understand the generalisability of the efficacy and safety outcomes and identify any new safety and efficacy concerns in relation to specific population group. The investigators propose the development of a registry for systematic collection of information with the dual aim of analysing the relationship between patient and treatment characteristics, and outcomes, and simultaneously identify areas for practice development that can improve the overall quality of life experienced by the haemophilia patient community.

Inclusion Criteria:

1. Patients with Haemophilia A or B requiring replacement therapy
2. Patients or parents able to provide informed consent
3. Patients being considered for use of EHL - CFC.

Exclusion Criteria:

1. Patients currently enrolled into a clinical trial of investigational medicinal product.

Patients with Haemophilia A or B requiring replacement therapy or being considered for use of EHL - CFC.