PB1237 - Bleeding diathesis in a girl with biallelic variants in RASGRP2 gene affecting platelet CalDAG-GEFI function

Tuesday, July 12, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: In-Person

Presenting Author(s)

Juan P. Frontroth, Biochemist

biochemist staff
Hospital de Pediatría "Prof. Dr. J.P.Garrahan"
CABA, Ciudad Autonoma de Buenos Aires, Argentina

Co-Author(s)

MH

Mirta D. Hepner

biochemist staff
Hospital de Pediatría "Prof. Dr. J.P.Garrahan"
CABA, Ciudad Autonoma de Buenos Aires, Argentina
Kate Downes, PhD

Lead Scientist
East Genomics, Cambridge Genomics Laboratory
Cambridge, England, United Kingdom
Carolina Cervio, MD

Pediatric Hematologist
Hospital de Pediatría "Prof. Dr. Juan P. Garrahan"
Buenos Aires, Buenos Aires, Argentina
SA

Silvina E. Annetta

Biochemist
Hospital de Pediatria Porf Dr Juan P Garrahan
CABA, Ciudad Autonoma de Buenos Aires, Argentina
Rodolfo E. Sueldo

Biochemist
Laboratorio de Hematología y Hemostasia. Hospital César Milstein
Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina
MB

Maria B. Bianco

Pediatric Hematologyst
Hospital de Pediatria Porf Dr Juan P Garrahan
CABA, Ciudad Autonoma de Buenos Aires, Argentina
GS

Gabriela B. Sciuccati, MD

Pediatric Hematologist
Hospital de Pediatría "Prof. Dr. J.P.Garrahan"
CABA, Ciudad Autonoma de Buenos Aires, Argentina

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.