Inherited platelet disorders are a heterogeneous group of rare diseases, caused by inherited defects in platelet production and/or function. Their genetic diagnosis would benefit clinical care, prognosis and preventative treatments. Until recently, this diagnosis has usually been performed via Sanger sequencing of a limited number of candidate genes. High-throughput sequencing is revolutionizing the genetic diagnosis of diseases, including bleeding disorders. We have designed a novel high-throughput sequencing platform to investigate the unknown molecular pathology in a cohort of 82 patients with inherited platelet disorders. Thirty-four (41.5%) patients presented with a phenotype strongly indicative of a particular type of platelet disorder. The other patients had clinical bleeding indicative of platelet dysfunction, but with no identifiable features. The high-throughput sequencing test enabled a molecular diagnosis in 70% of these patients. This sensitivity increased to 90% among patients suspected of having a defined platelet disorder. We found 57 different candidate variants in 28 genes, of which 70% had not previously been described. Following consensus guidelines, we qualified 68.4% and 26.3% of the candidate variants as being pathogenic and likely pathogenic, respectively. In addition to establishing definitive diagnoses of well-known inherited platelet disorders, high-throughput sequencing also identified rarer disorders such as sitosterolemia, filamin and actinin deficiencies, and G protein-coupled receptor defects. This included disease-causing variants in DIAPH1 (n=2) and RASGRP2 (n=3). Our study reinforces the feasibility of introducing high-throughput sequencing technology into the mainstream laboratory for the genetic diagnostic practice in inherited platelet disorders.

Background Careful assessment of bleeding history is the first step in the evaluation of patients with mild/moderate bleeding disorders, and the use of a bleeding assessment tool (BAT) is strongly encouraged. Although a few studies have assessed the utility of the ISTH‐BAT in patients with inherited platelet function disorders (IPFD) none of them was sufficiently large to draw conclusions and/or included appropriate control groups. Objectives The aim of the present study was to test the utility of the ISTH‐BAT in a large cohort of patients with a well‐defined diagnosis of inherited platelets disorder in comparison with two parallel cohorts, one of patients with type‐1 von Willebrand disease (VWD‐1) and one of healthy controls (HC). Patients/Methods We enrolled 1098 subjects, 482 of whom had inherited platelet disorders (196 IPFD and 286 inherited platelet number disorders [IT]) from 17 countries. Results IPFD patients had significantly higher bleeding score (BS; median 9) than VWD‐1 patients (median 5), a higher number of hemorrhagic symptoms (4 versus 3), and higher percentage of patients with clinically relevant symptoms (score > 2). The ISTH‐BAT showed excellent discrimination power between IPFD and HC (0.9 < area under the curve [AUC] < 1), moderate (0.7 < AUC < 0.9) between IPFD and VWD‐1 and between IPFD and inherited thrombocytopenia (IT), while it was inaccurate (AUC ≤ 0.7) in discriminating IT from HC. Conclusions The ISTH‐BAT allows to efficiently discriminate IPFD from HC, while it has lower accuracy in distinguishing IPFD from VWD‐1. Therefore, the ISTH‐BAT appears useful for identifying subjects requiring laboratory evaluation for a suspected IPFD once VWD is preliminarily excluded.

To cite this article: de la Morena-Barrio ME, Mart ınez-Mart ınez I, de Cos C, Wypasek E, Rold an V, Undas A, van Scherpenzeel M, Lefeber DJ, Toderici M, Sevivas T, España F, Jaeken J, Corral J, Vicente V. Hypoglycosylation is a common finding in antithrombin deficiency in the absence of a SERPINC1 gene defect. J Thromb Haemost 2016;14: 1549-60. Essentials• We investigated the molecular base of antithrombin deficiency in cases without SERPINC1 defects.• 27% of cases presented hypoglycosylation, transient in 62% and not restricted to antithrombin.• Variations in genes involved in N-glycosylation underline this phenotype.• These results support a new form of thrombophilia.

BackgroundThe diagnostic evaluation of inherited platelet disorders (IPDs) is complicated and time-consuming, resulting in a relevant number of undiagnosed and incorrectly classified patients. In order to evaluate the spectrum of IPDs in individuals with clinical suspicion of these disorders, and to provide a diagnostic tool to centers not having access to specific platelets studies, we established the project “Functional and Molecular Characterization of Patients with Inherited Platelet Disorders” under the scientific sponsorship of the Spanish Society of Thrombosis and Haemostasis.Patients/methodsSubjects were patients from a prospective cohort of individuals referred for clinical suspicion of IPDs as well as healthy controls. Functional studies included light transmission aggregation, flow cytometry, and when indicated, Western-blot analysis of platelet glycoproteins, and clot retraction analysis. Genetic analysis was mainly performed by sequencing of coding regions and proximal regulatory regions of the genes of interest.ResultsOf the 70 cases referred for study, we functionally and molecularly characterized 12 patients with Glanzmann Thrombasthenia, 8 patients with Bernard Soulier syndrome, and 8 with other forms of IPDs. Twelve novel mutations were identified among these patients. The systematic study of patients revealed that almost one-third of patients had been previously misdiagnosed.ConclusionsOur study provides a global picture of the current limitations and access to the diagnosis of IPDs, identifies and confirms new genetic variants that cause these disorders, and emphasizes the need of creating reference centers that can help health care providers in the recognition of these defects.

The diagnosis of von Willebrand disease (VWD), the most common inherited bleeding disorder, is characterised by a variable bleeding tendency and heterogeneous laboratory phenotype. The sequencing of the entire VWF coding region has not yet become a routine practice in diagnostic laboratories owing to its high costs. Nevertheless, next-generation sequencing (NGS) has emerged as an alternative to overcome this limitation. We aimed to determine the correlation of genotype and phenotype in 92 Portuguese individuals from 60 unrelated families with VWD; therefore, we directly sequenced VWF. We compared the classical Sanger sequencing approach and NGS to assess the value-added effect on the analysis of the mutation distribution in different types of VWD. Sixty-two different VWF mutations were identified, 27 of which had not been previously described. NGS detected 26 additional mutations, contributing to a broad overview of the mutant alleles present in each VWD type. Twenty-nine probands (48.3 %) had two or more mutations; in addition, mutations with pleiotropic effects were detected, and NGS allowed an appropriate classification for seven of them. Furthermore, the differential diagnosis between VWD 2B and platelet type VWD (n = 1), Bernard-Soulier syndrome and VWD 2B (n = 1), and mild haemophilia A and VWD 2N (n = 2) was possible. NGS provided an efficient laboratory workflow for analysing VWF. These findings in our cohort of Portuguese patients support the proposal that improving VWD diagnosis strategies will enhance clinical and laboratory approaches, allowing to establish the most appropriate treatment for each patient.