Comparison of phenotypic characteristics in carriers and non-carrier women of Hemophilia A and Hemophilia B

Abstract

Background: Hemophilia A (HA) and hemophilia B (HB) are monogenic bleeding disorders caused by pathogenic variants in the F8and F9 genes, respectively, which are located on the X chromosome and result in deficiencies of coagulation factor VIII (FVIII) and factor IX (FIX). The diseases predominantly affect males, while females are usually asymptomatic heterozygous carriers. Identification of female carriers among relatives of affected males is important for preventing bleeding complications associated with surgery and childbirth. Aim: The main aim of this study was to detect carrier and non-carrier women and compare some phenotypes. Materials and Methods: The study included 50 female relatives of 32 male patients diagnosed with hemophilia A and 13 female relatives of 8 male patients diagnosed with hemophilia B, giving a total of 63 female relatives. Molecular genetic testing was performed to identify the pathogenic variants previously detected in the probands and to determine the carrier status of female relatives. Among them, 33 confirmed carriers and 18 non-carriers completed a 28-item questionnaire comprising three sections to assess bleeding-related symptoms. The questionnaire evaluated easy bruising, duration of menstruation, postpartum bleeding, and bleeding following injuries, surgical procedures, and dental procedures. Questionnaire findings were compared between molecularly confirmed carriers and non-carriers. Continuous variables were compared using the Mann–Whitney U test, while categorical variables were analyzed using Fisher’s exact test in R software. In female relatives of patients with hemophilia A, plasma FVIII activity was also measured. Results: Molecular genetic testing was performed in 52 female relatives. Eleven women were excluded from carrier-status analysis because no pathogenic variant was identified in the F8 or F9 gene of their respective probands. Among 43 female relatives of patients with hemophilia A who underwent carrier testing, 26 (60.4%) were identified as carriers and 17 (39.5%) as non-carriers. Among eight male patients with hemophilia B, pathogenic F9 variants were identified in six; among their seven female relatives, six were confirmed carriers and one was a non-carrier. The mean FVIII activity among heterozygous HA carriers was 58.5±20.6 IU/dL (n=17), which was significantly lower than that of non-carriers (101±28.8 IU/dL; p<0.001). Of the nine bleeding-related symptoms assessed, only easy bruising of the skin was significantly more common among carriers (OR=6.8; p=0.0069). Although prolonged menstrual bleeding and bleeding after childbirth, surgery, or dental procedures were reported among some carriers, no statistically significant differences were observed between carriers and non-carriers. Conclusion: Among female relatives of males diagnosed with Hemophilia A or B in Mongolia, 32 (64%) of 50 women were identified as carriers and 18 (36%) as non-carriers. Plasma FVIII activity was significantly lower in HA carriers than in non-carriers (58.5±20.6 IU/dL vs. 101±28.8 IU/dL; p<0.001). Easy bruising was significantly more frequent among carriers (OR=6.8; p=0.0069). These findings support the importance of molecular genetic testing for identifying female carriers and recognizing women who may be at increased risk of bleeding, particularly in the context of surgery and childbirth.