Application of whole‐exome sequencing to direct the specific functional testing and diagnosis of rare inherited bleeding disorders in patients from the Öresund Region, Scandinavia

Abstract

SummaryRare inherited bleeding disorders (IBD) are a common cause of bleeding tendency. To ensure a correct diagnosis, specialized laboratory analyses are necessary. This study reports the results of an upfront diagnostic strategy using targeted whole exome sequencing. In total, 156 patients with a significant bleeding assessment tool score participated in the study, of which a third had thrombocytopenia. Eighty‐seven genes specifically associated with genetic predisposition to bleeding were analysed by whole exome sequencing. Variants were classified according to the five‐tier scheme. We identified 353 germline variants. Eight patients (5%) harboured a known pathogenic variant. Of the 345 previously unknown variants, computational analyses predicted 99 to be significant. Further filtration according to the Mendelian inheritance pattern, resulted in 59 variants being predicted to be clinically significant. Moreover, 34% (20/59) were assigned as novel class 4 or 5 variants upon targeted functional testing. A class 4 or 5 variant was identified in 30% of patients with thrombocytopenia (14/47) versus 11% of patients with a normal platelet count (12/109) (P < 0·01). An IBD diagnosis has a major clinical impact. The genetic investigations detailed here extricated our patients from a diagnostic conundrum, thus demonstrating that continuous optimization of the diagnostic work‐up of IBD is of great benefit.

A comprehensive targeted next‐generation sequencing panel for genetic diagnosis of patients with suspected inherited thrombocytopenia

“…This detection rate is in keeping with other recent previous large‐scale targeted panel sequencing studies and the application of WES to patients with IT of unknown etiology 4 , 12 , 20 , 21 . One possible explanation for the inflated detection rate for panel based platforms is the relative increase in average read coverage when compared to WES analysis, especially at the point of variation.…”

An update on the new classification of Ehlers‐Danlos syndrome and review of the causes of bleeding in this population

“…The use of whole exome sequencing in the diagnosis of inherited bleeding disorders (IBD) has the potential to identify pathogenic genetic variants already associated with well‐defined bleeding disorders. Recent studies have identified novel defects in collagen genes in patients with IBD . This highlights the importance of including an evaluation of collagen defects in a comprehensive evaluation of patients with bleeding disorders.…”

Outcome of an enhanced diagnostic pipeline for patients suspected of inherited thrombocytopenia

“…Since 2013, we have implemented WES as an upfront diagnostic method to diagnose patients suspected of inherited bleeding disorders, enabling a continuous update of novel discovered genes to be analysed. Following our recent publication (Leinoe et al , ), we have expanded the downstream specific testing guided by genetic results to include immunofluorescence microscopy, thrombopoietin level and CD34 expression on platelets. Since some IT may be caused by CNV, we validated a tool for CNV calling from WES data.…”