Abstract Number: PB0617
Meeting: ISTH 2021 Congress
Theme: Hemophilia and Rare Bleeding Disorders » Hemophilia - Clinical
Background: Mild-moderate (non-severe, NS) Hemophilia A (HA) associates with minor reduction in factor VIII (FVIII:C) (1-40IU/dL) and involve about 60% of HA cases worldwide. Despite the importance of NS-HA, patients are rarely genotyped, particularly in developing countries. Clinical manifestations and laboratory phenotype are frequently mistaken with VWD2N.
Aims: Characterize the F8-genotype and phenotype, exclude VWD2N, in a series of Argentine patients with FVIII:C 1-40IU/dL.
Methods: Thirty-eight unrelated-families including 50 individuals (probands and relatives) were studied. The bleeding phenotype was obtained from clinical records.
Laboratory: FVIII:C (one-stage method), VWF:Ag (ELISA), VWF:RCo (aggregometry). Mixing studies of the patient/control plasmas to evaluate the presence of inhibitors were undertaken by APTT and VWF:RCo.
Genotyping: peripheral blood leukocyte-extracted genomic-DNA was mutational screened by PCR-amplification of all coding and regulatory regions of the F8 followed by conformation sensitive gel electrophoresis (CSGE) and selected-amplimers were characterized by Sanger sequencing. Exons 17-27 of the VWF were PCR-amplified and directly Sanger-sequenced.
Results:
| Patients N † (%) |
F8 Domain | F8 Disease-causing variants†† |
FVIII:C X±SD |
VWF:Ag | VWF:RCo | Major bleeding (% of patients) |
|---|---|---|---|---|---|---|
| 3 (8) | A1 | c.601+5G>A c.602G>A p.(Gly201Glu) c.671-28_671-17del |
16±10.8 | 85±10.8 | 77±10.8 | 66.6 |
| 17 (45) | A2 | c.1214T>C p.(Ile405Thr) c.1313T>C p.(Ile438Thr) c.1372C>T p.(Arg458Cys) c.1475A>G p.(Tyr492Cys) (2x) c.1538-18G>A(2x) c.1569G>T p.(Leu523Leu) (3x) c.1636C>T p.(Arg546Trp) c.1834C>T p.(Arg593Cys) (3x) c.2027C>T p.(Thr676Ile) c.2128G>A p.(Gly710Arg) (2x) |
15.4±8.9 | 77±13.5 | 75±16 | 40 |
| 1 (2.5) | a3 | c.5096A>T; p.(Tyr1699Phe) | 20 | 76 | 90 | 0 |
| 1 (2.5) | B | c.3637delA p.(Ile1213Phefs*5) (A run) | 3 | 70 | 65 | 100 |
| 7 (18) | A3 | c.5428T>C p.(Ser1810Pro) (2x) c.5879G>T p.(Arg1960Leu) c.5912A>G p.(Asn1971Ser) c.5954G>A p.(Arg1985Gln) (2x) c.5981T>C p.(Leu1994Pro) |
22.6±9.7 | 108±22 | 90±10.9 | 42.8 |
| 3 (8) | C1 | c.6301C>G p.(His2101Asp) c.6505C>T p.(Arg2169Cys) c.6443A>G p.(Asn2148Ser) |
30±17.6 | 103±23.4 | 78±5.5 | 100 |
| 6 (16) | C2 | c.6683G>A p.(Arg2228Gln) c.6959T>C p.(Leu2320Ser) c.6967C>A p.(Arg2323Ser) c.6977G>A p.(Arg2326Gln) (2x) c.7054T>C p.(*2352Argext*34) |
9.3±5.2 | 75±19.6 | 76±25.8 | 40 |
| †N: number of families per specific F8 genotype; ††Human Genome Variant Society (HGSV) recommended nomenclature; RefSeq F8: NG_011403.1; F8 mRNA: NM_000132.3, FVIII Protein: NP_000123.1. | ||||||
Table 1: F8-genotype and the associated phenotype in the Argentinian population with NS-HA.
A HA-causative F8-genotype was identified in all 38 families including 28 pathogenic variants (PV) (Table 1). Eighteen (47%) of them showed 8 recurrent PV (range 2-3 families/PV), whereas the remnant 20 (53%) showed non-recurrent (private) F8-PV (Figure 1). No variants were found in VWF. Patients with major hemorrhages: 48.6%. Laboratory phenotype is shown in Table 1.
Molecular distribution of F8 variants characterized in our series of NS-HA patients.
Conclusions: Our practical approach is adequate to characterize the PV in NS-HA patients and relatives. The confirmed diagnosis of NS-HA allows an appropriate treatment and genetic counseling for X-linked inheritance highlighting the role of genetic testing and phenotypic assays. Combined HA+VWD2N was excluded in all patients.
The predominance of missense PV (30/38 cases, 79%) mostly targeting the FVIII-A2-domain and the high frequency of recurrent PVs found in NS-HA may reflect a reduced mutational loss due to the relatively conserved reproductive fitness of probands hence preserving the gene pool in the population.
To cite this abstract in AMA style:
Rossetti L, Woods AI, Blanco A, Paiva J, Marchione V, Radic CP, Abelleyro MM, Ziegler B, Waisman K, Romero ML, Casinelli MM, Sánchez-Luceros A, De Brasi C. Comprehensive Genotype Characterization in Non-severe Hemophilia A. Mutational Profile and Assessment of the Bleeding Phenotype in Argentine Patients [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/comprehensive-genotype-characterization-in-non-severe-hemophilia-a-mutational-profile-and-assessment-of-the-bleeding-phenotype-in-argentine-patients/. Accessed December 6, 2023.« Back to ISTH 2021 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/comprehensive-genotype-characterization-in-non-severe-hemophilia-a-mutational-profile-and-assessment-of-the-bleeding-phenotype-in-argentine-patients/