High prevalence of recurrent F8 genotypes in the first series of Argentine patients with mild hemophilia A

ROSSETTI LC; MARCHIONE VD; RADIC CP; ABELLEYRO MM; SANCHEZ LUCERO A; NEME D; CARLOS D. DE BRASI

Melbourne

Congreso; ISTH 2019; 2019

International Society on Thrombosis and Haemostasis

Background: Hemophilia A (HA),the commonest X-linked coagulopathy, is associated with deleterious variants inthe F8. Mild-HA patients show clottingactivities of factor VIII (FVIII:C) ranging 5-40 IU/dL. Although mild-HArepresents 35-40% of total HA cases, they are much less studied and genotypedthan severe cases worldwide. Both the theoretical basis and the scarce relatedliterature indicate that mild- and severe-HA (FVIII:C<1 IU/dL) associatewith substantial differences in its mutational pool turnover. Aims: To characterize the F8-genotype in a large series of Argentinepatients with mild-HA and to discuss its mutational dynamics. Methods: Sixty three apparentlyunrelated families affected with mild-HA were studied countrywide, including 96individuals (index-cases and relatives). Our F8 analysis algorithm includes: genomic-DNA extraction fromperipheral blood leukocytes, mutational screening by PCR-amplification of allcoding and regulatory regions of the F8covering all 26 exons (38 amplicons) followed by heteroduplex analysis by conformationsensitive gel electrophoresis (CSGE) and characterization of CSGE-anomalousamplimers by Sanger sequencing. Duplication of exon 13 (Dup13) was detected bytail-to-head PCR-analysis. Results: Mild-HA causative genotypes (established followinginternational genotype/phenotype assignment criteria) were identified in 60families (detection efficiency 95%). Thirty-four families (57%) showed 14recurrent mutations (each involved in 2-5 affected families), whereas theremnant 26 families (43%) showed non-recurrent (unique) F8-defects (Table 1). Conclusions: Our findings demonstratethat our practical approach is adequate to characterize the mild-HA causative F8-genotype in patients and relatives, highlightthe prevalence of missense variants in mild-HA (49/60, 82%) and indicate that the high frequency of recurrent F8-variants found in mild-HA may reflecta reduced mutational loss due to the relatively conserved reproductive fitness of the affected individual hence preservingthe mild-HA gene pool in our population.