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Geographic distribution of the type 2N VWD families studied in Italy and migration fluxes from Africa to Asia and Europe in the last 100,000 years.
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Background. The impaired capacity of von Willebrand factor (VWF) to carry factor VIII (FVIII) is identified as type 2N von Willebrand disease (VWD). R854Q is the most common type 2N mutation, and almost the only one identified in Italy. Design and methods. This study aimed to ascertain whether R854Q mutations in an Italian cohort of type 2N VWD pat...
Citations
... [10,13], and 2N (eg, p.Arg854Gln and p.Arg816Trp) [13,28]. Some of these variants are either at CpG mutation hotspots and/or were found in the context of founder haplotypes [59,60]. ...
von Willebrand disease (VWD) is the most common inherited bleeding disorder characterized by defects in the quantity or function of the von Willebrand factor (VWF). The diagnosis of VWD is complex, requiring a battery of tests to evaluate the amount, functions, and multimeric structure of the VWF glycoprotein. The diagnosis can also be accomplished or confirmed by sequencing the VWF gene (VWF). Genetic testing of the VWF has been around for four decades following the cloning of the VWF, and nowadays it has been integrated into the diagnostic panel of VWD. With the introduction of next-generation sequencing (NGS), genetic analysis of the VWF has become more practical compared to the past, when Sanger sequencing was used. A number of laboratories have applied or started to use genetic testing with NGS for VWD diagnosis. Considering the increasing application of genetic testing in VWD and the wide availability and decreasing cost of gene sequencing, we sought to discuss the challenges and considerations involved in applying genetic testing to VWD.
... Interestingly, 1 PWH was noted to have a significant reduction in VWF:FVIIIb (44%) and a reduced rFVIII half-life (8.2 hours) ( Figure 4B). The sequence analysis confirmed that this PWH was heterozygous for a missense variant p.(Arg854Gln) (rs41276738), a previously reported pathogenic variant in ClinVar in the D'D3 FVIII-binding region of the VWF gene, which is associated with type 2N VWD [38]. We also identified 20 PWH who were heterozygous for the reported variant p.(Gln852Arg) (rs216321), which was previously associated with reduced binding of FVIII in 1 patient [15]. ...
Background:
Previous studies have reported marked interindividual variation in factor VIII (FVIII) clearance in patients with hemophilia (PWH) and proposed a number of factors that influence this heterogeneity.
Objectives:
To investigate the importance of the clearance rates of endogenous von Willebrand factor (VWF) compared with those of other FVIII half-life modifiers in adult PWH.
Methods:
The half-life of recombinant FVIII was determined in a cohort of 61 adult PWH. A range of reported modifiers of FVIII clearance was assessed (including plasma VWF:antigen and VWF propeptide levels; VWF-FVIII binding capacity; ABO blood group; and nonneutralizing anti-FVIII antibodies). The FVIII-binding region of the VWF gene was sequenced. Finally, the effects of variation in FVIII half-life on clinical phenotype were investigated.
Results:
We demonstrated that heterogeneity in the clearance of endogenous plasma VWF is a key determinant of variable FVIII half-life in PWH. Both ABO blood group and age significantly impact FVIII clearance. The effect of ABO blood group on FVIII half-life in PWH is modulated entirely through its effect on the clearance rates of endogenous VWF. In contrast, the age-related effect on FVIII clearance is, at least in part, VWF independent. In contrast to previous studies, no major effects of variation in VWF-FVIII binding affinity on FVIII clearance were observed. Although high-titer immunoglobulin G antibodies (≥1:80) were observed in 26% of PWH, these did not impact FVIII half-life. Importantly, the annual FVIII usage (IU/kg/y) was significantly (p = .0035) increased in patients with an FVIII half-life of <12 hours.
Conclusion:
Our data demonstrate that heterogeneity in the half-life of FVIII concentrates in patients with hemophilia A is primarily attributable to variability in the clearance of endogenous VWF.
... was involved in double heterozygous VWD 2N (table 3). Casonato., et al. estimated that the most common R854Q mutation in VWD 2N occurred 10.000 to 40.000 years ago [22]. The R854Q mutation is limited to the Caucasian population suggesting that the R854Q mutational event occurred in the human population that had moved from Africa to Europe. ...
... The R854Q mutation is limited to the Caucasian population suggesting that the R854Q mutational event occurred in the human population that had moved from Africa to Europe. As compared to homozygous R854Q/R854Q VWD 2N (Table 3 Casonato [22]. cases 1 to 3), double heterozygous R854Q combined with the P812R null mutation in the D' domain is associated with severe FVIII:BSD of less than 15% (Table 3 Casonato, cases I-1and I-2) that decreased FVIII:C/VWF:Ag ratios and low values in the FVIII:BD assay ( Source: [31]. ...
Introduction: The FVIII binding site on von Willebrand factor (VWF) is located in the D’ (766-864) and D3 (1054-1060) regions of the VWF gene. The cysteine residues in the D’ domain Cys767-Cys808; Cys776-Cys804;Cys810-Cys821 form disulfide bridges be- tween two D’ trypsin-inhibitor-like (TIL’) and E’ regions, which are of critically importance for the binding between Til’E’ and FVIII. We analyzed the molecular etiology and laboratory phenotype of von Willebrand disease (VWD) 2N patients reported in the litera- ture and added personal experiences from three European VWF VWD Research Centers. Critical appraisal of the literature and personal experiences: Homozygous R854Q/R854Q and double heterozygous R854Q, E787K, T791M and R816W non-cysteine mutations in the D’ domain result in a FVIII binding defect (FVIII:BD) featured by mild to moderate hemophilia A with normal bleeding time and normal VWF functions and multimers consistent with VWD type 1. The FVIII:BD is mild in R854Q (about 30%) and markedly decreased (less than 10%) in E787K, T791M, R816W, D879N and C1060W either homozygous or double heterozygous with a null allele. VWF-FVIII binding defect due FVIII mutations in the C1 and C2 domain in FVIII gene mimic VWD 2N show low FVIII:C/VWF ratios below 0.50 with normal secretion and multimerization of VWF after DDAVP. The double heterozygous cysteine/null Y795C/null and cysteine/noncysteine Y795C/R854Q mutations produced VWD 2N with aberrant VWF multimers similar as seen in heterozygous Y795C/WT asymptomatic carriers. The VWF multimers in VWD 2N due to homozygous cysteine or cysteine/null mutations are abnormal. VWF multimers in double heterozygous cystein/non-cysteine C804F/R854Q and C858F/R854Q mutations are corrected to normal by the R854Q allele. Homozygous R760W/R760W (D2 do- main) and C788R/C788R (D’ domain) induce a recessive VWD type 2 secretion and multimerization defect with a mild FVIII:BD of about 35% without features of VWD 2N, whereas double heterozygous R854Q/R760W mutation in the D’D2 domains produce hy- brid phenotype 2N/2A VWD with a smeary pattern of VWF multimers due to a mixture of normal mature VWF and proVWF. Patients double heterozygous R854Q/R763G (Furin cleavage site) produce a hybrid VWD phenotype 2N/2A with a smeary VWF multimeric pattern due to a mixture of normal VWF and pro-VWF protein also seen in the heterozygous R763G/WT carriers. The homozygous C1060R/C1060R mutation in the D3 domain, and the double heterozygous D879N/null and C1060R/null mutations are associated with a hybrid phenotype of 2N/2E VWD. Conclusion: Classical VWD 2N caused by homozygous non-cysteine or double heterozygous non-cysteine/null mutations R854Q and R816W due to a FVIII binding defect (FVIII-BD) in D’ Domain of the VWF gene is featured by low FVIII;C, normal VWF levels and normal multimeric structure of VWF. Double heterozygous cysteine/noncystein mutations produce VWD type 2N with normal VWF multimers. The C760C in the D2 domain and the R763G Furin cleavage site mutations combined with the R854Q mutation produce a hybrid 2N/2A VWD phenotype associated with aberrant multimerization due to a mixture of mature VWF and pro VWF. Homozygous C1060R/C1060R and the double heterozygous D879N/null, C1060R/R854Q or C1060R/null mutations in the D3 domain are associ- ated with a hybrid 2N/2E VWD phenotype
... Od tego czasu opisano wiele przypadków 2N VWD na całym świecie. Badania epidemiologiczne pokazują, że typ 2N VWD występuje stosunkowo rzadko i stanowi 1-2% wszystkich chorych z VWD [34,35]. Fenotypowo 2N VWD może przypominać łagodną lub umiarkowaną hemofilię A, różni się jednak od niej sposobem dziedziczenia [32,33,36]. ...
... Mutacje te są zlokalizowane w obszarze pierwszych 272 aminokwasów monomeru VWF w domenach D'D3 [35,48], przy czym mutacje w eksonach 18-20 kodujących domenę D' VWF stanowią około 85% wszystkich opisanych mutacji typu 2N, natomiast pozostałe 15% zachodzi w eksonach 17 i 21-27 [37,45,47]. ...
... Najczęściej występującą mutacją w populacji europejskiej jest R854Q. Występuje ona u 73% wszystkich opisanych dotychczas pacjentów z typem 2N VWD [35,61]. Badania Casonato i wsp. ...
Choroba von Willebranda (VWD) typu 2N jest to skaza krwotoczna, która dziedziczy się autosomalnie recesywnie i jest klinicznie podobna do łagodnej hemofilii A. W typie 2N VWD zmniejszone powinowactwo czynnika von Willebranda (VWF) do czynnika VIII (FVIII) jest spowodowane mutacjami w miejscu wiązania FVIII lub zmianami konformacyjnymi cząsteczki VWF, upośledzającymi interakcję VWF-FVIII. Laboratoryjnie typ 2N VWD charakteryzuje się nieproporcjonalnie obniżonym FVIII do antygenu VWF i w efekcie zredukowanym ilorazem FVIII/VWF:Ag. U większości pacjentów z 2N VWD stężenie i struktura multimetrów VWF są prawidłowe. Rozpoznanie VWD 2N opiera się głównie na oznaczeniu obniżonego wiązania FVIII do VWF lub zidentyfikowaniu mutacji sprawczych w domenie genu VWF, odpowiedzialnej za wiązanie FVIII. Typ 2N VWD powinien być zawsze brany pod uwagę u pacjentów z niskim stężeniem FVIII.
... The defect is transmitted as a recessive autosomal trait, and homozygotes have reduced FVIII levels, usually associated with normal VWF levels, as seen in mild or moderate haemophilia A. Type 2N genetic defects generally (in 85% of cases) occur in exons 18 to 20 of the VWF gene, encoding for the D' domain, sociated with the persistence of VWF propeptide, which impairs the capacity of VWF to bind FVIII.13 A previous study of ours demonstrated that the p.R854Q mutation appeared in the Italic population more than 10 000 years ago and that all the individuals studied so far have a progenitor in common.24 Main haemostatic findings of heterozygous type 2N von Willebrand disease (VWD) subjects high expressivity of the type 2N defect in these particular cases. ...
Introduction:
An abnormal factor VIII (FVIII) binding capacity of von Willebrand factor (VWF) identifies type 2N von Willebrand disease (VWD). Type 2N VWD patients are identified by means of the VWF FVIII binding (VWF:FVIIIB) assay, and especially their VWF:FVIIIB/VWF:Ag ratio (VWF:FVIIIB ratio).
Aim:
We report on our 15-year experience of diagnosing type 2N VWD.
Methods:
We have performed 2178 VWF:FVIIIB assays in bleeders and normal subjects.
Results:
von Willebrand factor (VWF):FVIIIB was reduced in 682, but only 60 had low VWF:FVIIIB ratios (<0.74). Among nine patients who had a VWF:FVIIIB ratio below 0.3, four had normal VWF levels and were homozygotes for the p.R854Q mutation; the other five had low VWF levels due to a quantitative VWF mutation combined with p.R854Q. The VWF:FVIIIB ratio ranged between 0.3 and 0.73 in 51 subjects; 34 of them were heterozygotes for the p.R854Q mutation, while one carried the p.R760C. The heterozygotes for type 2N included subjects with or without bleeding symptoms, the former with significantly lower mean VWF levels than the latter. Among the 116 normal subjects tested, six were heterozygotes for the p.R854Q mutation (all asymptomatic).
Conclusions:
The prevalence of type 2N in our VWD cohort was 2.5%, and 5.2% of the general population in Northeast Italy was found heterozygous for the p.R854Q mutation. It might be difficult to reveal a type 2N defect using routine tests alone, especially when it is combined with a quantitative VWF mutation. Accordingly, we always recommend VWF:FVIIIB assay in the diagnostic workup of VWD.
Glanzmann thrombasthenia is a rare autosomal recessive inherited bleeding disorder characterized by the lack of platelet aggregation, caused by deficiencies and/or abnormalities of platelet GPIIb-IIIa receptor. We report a case of Glanzmann thrombasthenia combined with type 2N von Willebrand disease (VWD), a variant characterized by an impaired capacity of FVIII to bind von Willebrand factor (VWF), which results in an autosomally transmitted reduction in circulating FVIII levels. Glanzmann thrombasthenia stems from compound T1214C and G1234A mutations in the ITGA2B gene; the type 2N VWD is due to a heterozygous G2561A mutation in the VWF gene (R854Q). The haemostatic phenotype of a 48-year-old female patient was unusually characterized by a severe chronic arthropathy with loss of cartilage and the presence of subchondrial cysts involving both ankles. The arthropathy was quantified with the compatible MRI scoring system (currently used to assess arthropathy in haemophilia), reaching almost the highest score. These haemorrhagic complications are very rare in Glanzmann thrombasthenia and resemble those seen in severe haemophilia; for such, a reason we decided to explore the patient's FVIII and VWF parameters. Our findings suggest that the type 2N R854Q mutation, which is normally asymptomatic at the heterozygous level, may be expressed in the presence of a combined impairment of primary haemostasis.
