Difference between haemophilia A and B

March 2020 Medical Research Marjolein Groot

Haemophilia is a rare, hereditary disease that mostly affects men. This disease results in an incorrect blood coagulation and in consequence longer bleedings. Haemophilia occurs in two sub-types: haemophilia A and haemophilia B. In haemophilia A, there is a lack or total absence of coagulation factor VIII. In haemophilia B, there is a serious shortage or total absence of coagulation factor IX.

Severity of illness

The lower the presence of the coagulation factor, the more severe the haemophilia. When the coagulation factor is entirely absent, internal bleedings can arise in joints, muscles, organs or soft tissue. Without treatment, this can cause serious damage to the musculoskeletal system.

Haemophilia is present in around 1:10.000 people worldwide and about 85% of the patients suffer from haemophilia A.2 Until now, there did not seem to be a huge difference between the two types in how much the patient suffers from it. However, a new study from dr. Ullman and colleges has provided the new insight that haemophilia B patients are generally doing better than haemophilia A patients.3

Severity score

On average, haemophilia A patients ranked higher on the haemophilia severity score, than haemophilia B patients. Furthermore, haemophilia A patients required arthroplasty more often, which is a type of surgery to repair or replace. Additionally, severe haemophilia A patients suffered from more bleedings than severe haemophilia B patients. This was true for both internal and external bleeds.3

Moreover, haemophiliacs can receive injections with their missing coagulation factor, to compensate the shortage. Haemophilia B patients required a lower dosage of the missing coagulation factor (on average 0,29 IU) compared to A (on average 1,66 IU). The percentage of patients that regularly needed to receive this medicine as a precaution was also lower in B (32%) than in A (69%).

All of these factors together contribute to the conclusion that on average, patients with haemophilia A suffer more from their disease than haemophilia B patients.


  1. Haemophilia.org
  2. Hirayama AB, Silva AKCD, Rocha JS, Roberti MDRF. (2019). Prevalence of symptoms in hemophilia carriers in comparison with the general population: a systematic review. Hematology, transfusion and cell therapy41(4), 349-355.
  3. Ullman M. M. et al., Is Hemophilia B Clinically Less Severe Than Hemophilia a? Evidence from the Hugs Va and Vb Studies. Blood 2019; 134 (1): 58
  4. Margaglione M, Castaman G, Morfini M, et al. The Italian AICE-Genetics hemophilia A database: results and correlation with clinical phenotype. Haematologica. 2008;93:722–8. 
  5. Belvini D, Salviato R, Radossi P, et al. Molecular genotyping of the Italian cohort of patients with hemophilia B. Haematologica. 2005;90:635–42. 

Further reading

Visit the website of patient organization AHVH for further information on haemophilia and related topics.