PB0357 - Type 2B von Willebrand disease: a 27-year registry of a single tertiary pediatric center in Argentina.

Sunday, June 23, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Co-Author(s)

MB

María Belén Bianco

Pediatric hematologist staff
Hospital de Pediatría Prof. Dr. J.P. Garrahan
CABA, Ciudad Autonoma de Buenos Aires, Argentina
MH

Mirta Hepner

Biochemist staff
Hospital de Pediatría Prof. Dr. J.P. Garrahan
CABA, Ciudad Autonoma de Buenos Aires, Argentina
Carolina Cervio

Pediatric hematologist staff
Hospital de Pediatría Prof. Dr. J.P. Garrahan
CABA, Ciudad Autonoma de Buenos Aires, Argentina
AC

Alejandro Chaves

Biologist
Hospital de Pediatri Prof Dr Juan P Garrahan
Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina
CP

Carolina M Pepe

Biochemist staff
Hospital de Pediatría Prof. Dr. J.P. Garrahan
CABA, Ciudad Autonoma de Buenos Aires, Argentina
Silvina Eliana Annetta

Biochemist
Hospital de Pediatria Prof Dr JP Garrahan
Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina
ES

Emanuel Sueldo

Biochemistry
Hospital Dr. Cesar Milstein
CABA, Ciudad Autonoma de Buenos Aires, Argentina
GS

Gabriela Sciuccati

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

Presenting Author(s)

Juan Pablo Frontroth, Biochemist

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

Background: Type 2B von Willebrand disease(2B-VWD) is characterized by an increased affinity of VWF to platelet GPIb and defined by platelet agglutination with low dose ristocetin induced platelet aggregation (ldRIPA) and/or a known variant in exon 28 of vWF gene.

Aims: To describe a cohort of patients diagnosed with 2B-VWD (p2B-VWD) at a tertiary care pediatric center.

Methods: Single-center observational study. From June/1996 to December/2023,patients < 18 years old with VWD were prospectively registered. p2B-VWD were selected for analysis.
Bleeding severity was evaluated with the ISTH-BAT score(BAT). Subjects admitted before 2010 were reassessed to calculate BAT.
Routine coagulation measurements, VWF:Ag and VWF:RCo, RIPA at low dose ristocetin (0.5 mg/mL) and minimal ristocetin concentration were performed. RIPA mixing studies were done to rule out PT-VWD. Exon28 VWF gene was analyzed by Sanger. Clinical data, laboratory, treatment and outcomes were recorded. Results are expressed as median(range).

Results: Among 295 patients diagnosed with VWD, 41 subjects from 18 unrelated families were classified as 2B-VWD:28children, prevalence (CI95%):9.5%(6.1-12.8), 17(61%)female,age 6.7(0.9-17.5)years and 13 relatives.
Clinical evaluation of the 28 children at baseline: extensive bruising, 18(64%); epistaxis, 16(57%) and abnormal menstrual bleeding, 1(4%). 11/13 affected relatives had bleeding symptoms. 7/28 children showed thrombocytopenia: 3(11%) at baseline, 4(14%) exposed to stress conditions, 5/7 required red blood transfusion. 17/28 children were followed prospectively at our center during 8-years(2.7-13.8), 8/17(47%) required VW concentrates.
Genetic analyses were performed in all children and a genotype-phenotype correlation was present in 92.6% of cases. Eleven VWF genetic variants were identified.
Table 1 shows patients` characteristics.

Conclusion(s): In this pediatric cohort of 2B-VWD most of the patients had abnormal bleeding score. Children with thrombocytopenia experienced the most severe bleeding symptoms.
The use of ldRIPA and RIPA mixing studies allow us to indentify pVWD2B.
Diagnosis of 2B-VWD may be challenging because patients do not always present with thrombocytopenia or show hiperaggregation.