The Bleeding Assessment Tool and laboratory data in the characterisation of a female with inherited haemophilia A

Abstract

Introduction
Haemophilia A (HA) is an X-linked recessive bleeding disorder caused by a deficiency or functional impairment of coagulation factor VIII (FVIII). HA has a worldwide prevalence of approximately 1 in 5,000 males. Based on residual FVIII activity, the disease is classified as severe (FVIII:C below 1%), moderate (FVIII:C 1-5%), or mild (FVIII:C 5-30%)1,2. Among patients with severe HA, intron 22 inversion (Inv22) in the FVIII gene (F8) is the most common genetic anomaly, accounting for at least 30-40% of cases3,4. Inv22 mutation results from homologous recombination of the int22h-1 region in the F8 locus with the int22h-2 (Inv22 type 1, Inv22-1) or int22h-3 (Inv22 type 2, Inv22-2) regions lying about 400 Kb distal from F85. Female HA carriers are usually asymptomatic because the presence of a single copy of normal F8 suffices to ensure the production of sufficient concentrations of FVIII for haemostasis6. There are, however, some reports of HA females who bleed. [...]