High-throughput sequencing approaches for diagnosing hereditary bleeding and platelet disorders

Hereditary bleeding and platelet disorders (BPDs) are characterized by marked genetic heterogeneity, far greater than previously appreciated. The list of genes involved in the regulation of megakaryopoiesis, platelet formation, platelet function and bleeding has been growing rapidly since the introduction of high-throughput sequencing (HTS) approaches in research. Thanks to the gradual adoption of HTS in diagnostic practice, these discoveries are improving the diagnostic yield for BPD patients, who may or may not present with bleeding problems and often have other clinical symptoms unrelated to the blood system. However, it was previously found that screening for all known etiologies gives a diagnostic yield of over 90% when the phenotype closely matches a known BPD but drops to 10% when the phenotype is indicative of a novel disorder. Thus, further research is needed to identify currently unknown etiologies for BPDs. Novel genes are likely to be found to be implicated in BPDs. New modes of inheritance, including digenic inheritance, are likely to play a role in some cases. Additionally, identifying and interpreting pathogenic variants outside exons is a looming challenge that can only be tackled with an improved understanding of the regulatory landscape of relevant cell types and with the transition from targeted sequencing to whole-genome sequencing in the clinic.