[The clinical characteristics and molecular pathogenesis of a variant Glanzmann's thrombasthenia-like pedigree]

RasGRP2 Structure, Function and Genetic Variants in Platelet Pathophysiology

RasGRP2 is calcium and diacylglycerol-regulated guanine nucleotide exchange factor I that activates Rap1, which is an essential signaling-knot in "inside-out" αIIbβ3 integrin activation in platelets. Inherited platelet function disorder caused by variants of RASGRP2 represents a new congenital bleeding disorder referred to as platelet-type bleeding disorder-18 (BDPLT18). We review here the structure of RasGRP2 and its functions in the pathophysiology of platelets and of the other cellular types that express it. We will also examine the different pathogenic variants reported so far as well as strategies for the diagnosis and management of patients with BDPLT18.

RASGRP2 gene variations associated with platelet dysfunction and bleeding

This manuscript reviews pathogenic variants in RASGRP2, which are the cause of a relatively new autosomal recessive and nonsyndromic inherited platelet function disorder, referred to as platelet-type bleeding disorder-18 (BDPLT18)(OMIM:615888). To date, 18 unrelated BDPLT18 pedigrees have been reported, harboring 19 different homozygous or compound heterozygous RASGRP2 variants. Patients with this disease present with lifelong moderate to severe bleeding, with epistaxis as the most common and relevant bleeding symptom. Biologically, they exhibit normal platelet count and morphology, reduced aggregation responses to ADP, epinephrine and low-dose collagen, and impaired αIIbβ3 integrin activation (fibrinogen or PAC-1 binding) in response to most agonists except PMA. Diagnosis is confirmed by genetic analysis of RASGRP2.