Molecular analysis of mild hemophilia patients in Argentina: Duplication of exon 13 an uncommon recurrent mutation in our country.

MARCHIONE VD; RODRIGUEZ R; DE BRASI CD; RADIC CP; SANCHEZ LUCERO A; ROSSETTI LC; ABELLEYRO MM; NEME D

Mar del Plata

Congreso; Reunión Conjunta LXIII Sociedad Argentina de Investigación Clínica (SAIC) - LXVI Sociedad Argentina de Inmunología (SAI) ? Sociedad Argentina de Fisiología (SAFIS) 2018; 2018

Sociedad Argentina de Investigación Clínica (SAIC) - Sociedad Argentina de Inmunología (SAI) ? Sociedad Argentina de Fisiología (SAFIS)

Haemophilia A (HA) is the commonest X-linkedcoagulopathy caused by deleterious mutations in F8. Mild-HA associates with minor reduction in the clotting activityof factor VIII (FVIII:C) to 5-40 UI/dL. Perhaps due to their mild phenotypeexpression, mild-HA patients are rarely genotyped although they represent35-40% of HA cases worldwide. The scarce published data indicate that mild-HAshows notable differences with severe-HA (FVIII:C<1 IU/dL) in its populationgenetics and mutational pool turnover. Objective: to characterise the F8-genotype in a large series of Argentine patients with mild-HAand to discuss its mutational dynamics. Population: 64 apparently unrelated familiesaffected with mild-HA countrywide, 97 individuals including index-cases andrelatives. Our F8 analysis algorithmincludes: -genomic DNA extraction from peripheral blood leukocytes, -amutational screening by PCR-amplification of all coding and regulatory regions ofF8 over all 26 exons (38 amplimers)and conformation sensitive gel electrophoresis (CSGE), -mutationalcharacterisation by Sanger sequencing of CSGE anomalous amplimers. Duplicationof exon 13 (Dup13) was detected by tail-to-head PCR-analysis. The mild-HA-causative mutation (established bygenotype/phenotype assignment criteria) was identified in 61 families (detectionefficiency 95%). Thirty-four families (56%) showed 14 recurrent mutations(repeated 2-5 times), whereas the remnant 27 families, non-recurrent F8-defects. Among the recurrentmutations, we found 11 missense in 26 families highlighting p.Arg612Cys* (n=5)and p.Arg550Cys (n=3) among others (n=2), a splicing defect on c.601+5G>A(n=3), the Dup13* (n=3) and a synonym change (n=2) (*reported with Italianorigin). Non-recurrent mutations included 24 missense, an ins-del and two splicing defects. Our findings demonstrate that our practical approachis adequate to characterise the mild-HA-causative F8-genotype in patients and relatives, highlight the prevalence ofmissense defects in mild-HA (50/61, 82%) and indicate that the higher frequencyassessed for recurrent mutations in mild-HA respect to severe-HA may reflectthe higher mutational turnover of the severe-HA pool.