An orthopaedic assessment of the joint status of seven severe haemophiliacs (mean age 12.5 y - range 8.9-15.5) on prophylactic treatment (PT) by magnetic resonance imaging (MRI) and physical examination was carried out. Median duration of PT of these patients was 84 months (range 32-107). A locally designed MRI joint score considering seven parameters (1 - joint effusion, 2 - synovial membrane thickening, 3 - haemosiderin deposits, 4 - joint cartilage injury, 5 - subchondral bone erosion, 6 - subchondral bone cysts, 7 - osteonecrosis) was used (maximum score = 13 points). MRI scans were performed in 17 joints (nine ankles, seven knees and one elbow): mean MRI scores for the affected joints was 5.1. A poor consistency between physical examination and MRI findings or the real extent of joint damage was found (Cohen kappa index 0.320). MRI is a precise non-invasive tool for the assessment of early joint cartilage and synovium pathological changes still undetectable by physical examination or conventional X-rays in the haemophilic setting.

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The multimeric analysis (MA) of plasma von Willebrand factor (VWF) evaluates structural integrity and helps in the diagnosis of von Willebrand disease (VWD). This assay is a matter of controversy, being considered by some investigators cumbersome and only slightly informative. The centralised study ‘Molecular and Clinical Profile of von Willebrand Disease in Spain (PCM-EVW-ES)’ has been carried out by including the phenotypic assessment and the genetic analysis by next generation sequencing (NGS) of the VWF gene (VWF). The aim of the present study was to evaluate the role of MA to the diagnosis of these patients and their potential discrepancies. Two hundred and seventy out of 480 patients centrally diagnosed with VWD had normal multimers, 168 had abnormal multimers and 42 a total absence of multimers. VWF MA was of great significance in the diagnosis of 83 patients (17.3%), it was also of help in the diagnosis achieved in 365 additional patients (76%) and was not informative in 32 cases (6.7%). With regard to discrepancies, 110 out of 480 (23%) patients centrally diagnosed with VWD presented some kind of discordance between VWF:RCo/VWF:Ag and/or VWF:CB/VWF:Ag ratios, multimeric study and/or genetic results. The VWF MA was key in the presence of novel mutations as well as in cases with phenotypic discrepancies. A comparison between the contribution of MA and VWF:CB showed a clearly higher contribution of the former in the diagnostic process. These data seem to reinforce the relevance of the VWF MA in VWD diagnosis, despite all its limitations.

Large studies in von Willebrand disease patients, including Spanish and Portuguese registries, led to the identification of >250 different mutations. It is a challenge to determine the pathogenic effect of potential splice site mutations on VWF mRNA. This study aimed to elucidate the true effects of 18 mutations on VWF mRNA processing, investigate the contribution of next-generation sequencing to in vivo mRNA study in von Willebrand disease, and compare the findings with in silico prediction. RNA extracted from patient platelets and leukocytes was amplified by RT-PCR and sequenced using Sanger and next generation sequencing techniques. Eight mutations affected VWF splicing: c.1533+1G>A, c.5664+2T>C and c.546G>A (p.=) prompted exon skipping; c.3223-7_3236dup and c.7082-2A>G resulted in activation of cryptic sites; c.3379+1G>A and c.7437G>A) demonstrated both molecular pathogenic mechanisms simultaneously; and the p.Cys370Tyr missense mutation generated two aberrant transcripts. Of note, the complete effect of three mutations was provided by next generation sequencing alone because of low expression of the aberrant transcripts. In the remaining 10 mutations, no effect was elucidated in the experiments. However, the differential findings obtained in platelets and leukocytes provided substantial evidence that four of these would have an effect on VWF levels. In this first report using next generation sequencing technology to unravel the effects of VWF mutations on splicing, the technique yielded valuable information. Our data bring to light the importance of studying the effect of synonymous and missense mutations on VWF splicing to improve the current knowledge of the molecular mechanisms behind von Willebrand disease. clinicaltrials.gov identifier:02869074 .

Factor VIII (FVIII) activation by thrombin leads to proteolytic cleavage and loss of B-domain and formation of a heterotrimeric structure constituted by A2 domain linked by weak ionic interactions to A1 and A3-C1-C2 subunit. Dissociation of the A2 domain results in the formation of the heterodimeric inactive FVIII molecule. About 5% of haemophilia A patients show a normal concentration of FVIII antigen (FVIII:Ag) levels (at least 30% of normal) but markedly reduced FVIII activity (FVIII:C) suggesting dysfunctional FVIII protein; this type of haemophilia is known as cross-reacting material positive (CRM+) [1]. A subset of these patients with a mild phenotype exhibit a discrepancy between FVIII:C results elicited in one-stage and two-stage assays [2-4] and 11 mutations in the A1, A2, A3 and C domains have been identified so far as responsible for that in vitro phenomenon [5]. Arg 531 His is one of the best-characterized mutations, its molecular basis consisting of an increase in the dissociation rate of the A2 subunit from the activated FVIII (FVIIIa) heterotrimer which leads to increased rate of inactivation and discrepancies in the plasma FVIII concentrations elicited with different assays and assay conditions [3,6]; Arg 1966 Gln is, however, the most frequently found (10% of mild haemophiliacs overall and 38% of discrepant patients) and has similar pathogenetic consequences [5].