Phenotypic variation in severe hemophilia A is related to endogenous thrombin potential and plasma levels of factor VII.

Hemophilia A is a bleeding disorder caused by deficiency or low activity of circulating factor VIII characterized by prolonged blood coagulation time and often spontaneous bleeding. Patients with the severe form of the disease may present considerable heterogeneity in the occurrence of bleeding episodes and some of them have a mild hemophilia A phenotype. This study aimed to evaluate the association of biomarkers and coagulation parameters to the differential hemorrhagic profile of severe hemophilia A patients. Polymorphisms in the genes of proteins C and S, factors V and VII and prothrombin were evaluated in a group of severe hemophilia A patients with a broad spectrum of bleeding profile. Plasma levels of coagulation factors and thrombin generation were also analyzed. This study included 59 Brazilian hemophilia A patients who were allocated into low bleeding profile (LBP; n = 33) and high bleeding profile (HBP; n = 26) groups based on their joint and muscle bleeding episodes requiring treatment in the 5 years before inclusion in the study. Results evidenced that endogenous thrombin potential (ETP) and plasma factor VII levels were significantly higher in the LBP group. Results indicate a prominent importance of FVII plasma activity and endogenous thrombin potential on the differential bleeding phenotype of hemophilia A patients.

Genetic variants of VWF gene in type 2 von Willebrand disease.

INTRODUCTION: von Willebrand disease (VWD) is the most common inherited bleeding disorder. Few studies have explored the molecular basis of type 2 VWD. AIM: This study aimed to identify variants associated with type 2 VWD. METHODS: We collected clinical and laboratory data, as well as response to desmopressin and bleeding assessment tool (BAT) score in patients diagnosed with type 2 VWD. We sequenced exons 17, 18, 20 and 28 of the VWF gene. RESULTS: We identified 19 different variants in 40 unrelated patients (47.5%). Most of the variants (84.2%) were found in exon 28. A total of 10/19 variants (52.6%) were identified as "likely causative" in 17/40 patients (42.5%), according to the ISTH-SSC and EAHAD VWF gene mutations databases. Nine variants were initially identified as potentially benign. However, through analyses in silico, four of these variants were reclassified as "likely pathogenic" (Ile1380Val, Asn1435Ser, Ser1486Leu and Tyr1584Cys). Response to desmopressin was associated with three variants: Met740Ile, Arg1597Gln and Tyr1584Cys. Major bleeding was associated with variants related to VWD subtypes 2B and 2M. CONCLUSION: In conclusion, we identified 19 variants, of which 14 are "likely pathogenic" and therefore associated with VWD. We suggest a possible association of pathogenic variants with major bleeding, response to desmopressin and BAT score ≥10, although this requires further confirmation.