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Bleeding diathesis in a girl with biallelic variants in RASGRP2 gene affecting platelet CalDAG-GEFI function

1Hospital de Pediatría Prof Dr Juan P Garrahan, Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina, 2Laboratorio de Hemostasia y Trombosis. Servicio de Hematología y Oncología. Hospital de Pediatría Prof Dr Juan P Garrahan, Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina, 3Cambridge Genomics Laboratory, Cambridge University Hospital NHS Foundation Trust, Cambridge, UK, Cambridge, England, United Kingdom, 4Laboratorio de Hemostasia y Trombosis. Servicio de Hematología y Oncología. Hospital de Pediatría Prof Dr Juan P GarrahanLaboratorio de Hemostasia y Trombosis. Servicio de Hematología y Oncología. Hospital de Pediatría Prof Dr Juan P Garrahan, Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina, 5Laboratorio de Hematología. Hospital Dr. César Milstein, Hospital de Pediatría Juan P. Garrahan, Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina, 6Servicio de Hematología y Oncología. Hospital de Pediatría Prof Dr Juan P GarrahanLaboratorio de Hemostasia y Trombosis. Servicio de Hematología y Oncología. Hospital de Pediatría Prof Dr Juan P Garrahan, Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina, 7Servicio de Hematología y Oncología. Hospital de Pediatría Prof Dr Juan P Garrahan, Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina

Abstract Number: PB1237

Meeting: ISTH 2022 Congress

Theme: Platelet Disorders, von Willebrand Disease and Thrombotic Microangiopathies » Platelet Function Disorders, Hereditary

Background: The RASGRP2 gene encodes the Ca2+ and DAG-regulated guanine nucleotide exchange factor (CalDAG-GEFI). Variants of this gene lead to BDPLT-18 disorders (OMIM 615888). Platelet granules release dysfunction was reported with variable responses

Aims: To report a compound heterozygous RASGRP2 variants and phenotypic findings in a girl with severe bleeding symptoms

Methods: Screening coagulation tests plus VWF:Ag and VWF:RCo were performed.

Blood smears were analyzed by optic microscopy. Platelet glycoprotein expressions were quantified by flow cytometry. Platelet aggregation in response to ADP, collagen, arachidonic acid, epinephrine and ristocetin were investigated by LTA. ATP release was determined by Lumi-aggregometry. Patient’s DNA was analyzed by next-generation sequencing (NGS), of known platelet function genes (Thrombo Genomics, Cambridge, UK).

Results: A five-year-old girl presented with severe and recurrent epistaxis requiring frequent hospitalizations and blood transfusions (ISTH-BAT score= 7). Routine coagulation profile, VWF:Ag and VWF:RCo were normal. Blood smear examination showed large platelets with some vacuolated ones. Flow cytometry showed normal expression of IIb3 and GPIb. Platelet aggregation in response to ADP, epinephrine, arachidonic acid, ristocetin and low collagen concentration was impaired. Collagen at high concentration showed a normal profile. ATP release was defective in response to all agonists assessed. A known missense variant (NM_153819.1, p.Gly305Asp) and a novel intronic splice site deletion (c.814-16_814-5delTGTCCTTTGTCC) in RASGRP2 were identified using NGS.

Conclusion(s): We identified compound heterozygous RASGRP2 variants affecting CalDAG-GEFI function and leading to BDPLT-18 disorder in a patient with severe bleeding symptoms. To our knowledge, only a few patients with BDPLT-18 have been described so far. We could not assign the impaired ATP release to any variant tested in the NGS panel, so we hypothesized an unrevealed mechanism in which CalDAG-GEFI dysfunction affects platelet granules release.

To cite this abstract in AMA style:

Frontroth J, Hepner M, Downes K, Cervio C, Annetta S, Sueldo R, Bianco B, Sciuccati G. Bleeding diathesis in a girl with biallelic variants in RASGRP2 gene affecting platelet CalDAG-GEFI function [abstract]. https://abstracts.isth.org/abstract/bleeding-diathesis-in-a-girl-with-biallelic-variants-in-rasgrp2-gene-affecting-platelet-caldag-gefi-function/. Accessed September 21, 2023.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/bleeding-diathesis-in-a-girl-with-biallelic-variants-in-rasgrp2-gene-affecting-platelet-caldag-gefi-function/