AlphaIIbG236E causes Glanzmann thrombasthenia by impairing association with beta3

Bleeding Phenotype of Glanzmann Thrombasthenia (GT) and Treatment Outcomes in Over One Hundred Patients: A Two-Center Experience in North Pakistan

BACKGROUND

Glanzmann thrombasthenia (GT) is a rare disease with an autosomal recessive inheritance pattern. This disorder is not so uncommonly encountered in routine clinical practice and laboratory settings in Pakistan let alone in the rest of the world. To describe the bleeding phenotype of GT and treatment outcomes in over one hundred patients in north Pakistan.

MATERIALS AND METHODS

This descriptive, cross-sectional, retrospective study was conducted on patients from 2011 to 2023 using a convenience sampling technique. A total of 103 patients of all ages and both genders diagnosed as having inherited GT were included in the study.

RESULTS

The median age of the study population was 1.1 years, with an interquartile range (IQR) of 0.8-2. Out of the total, 55 (53%) patients were males and 48 (47%) patients were females. Ninety-eight percent of patients were diagnosed using light transmission aggregometry, and only two (2%) patients were diagnosed by immunophenotyping. Due to the high incidence of interfamily marriages, 86 (84%) patients were born to consanguineous marriages. Thirty-nine (38%) patients had an episode of major bleeding as defined by the International Society on Thrombosis and Haemostasis (ISTH) criteria. Epistaxis in 73 (71%) patients, skin bruising in 63 (61%), and gum bleeding in 57 (55%) were the most common bleeding symptoms. Thirty-two (31%) required the use of r-VIIa for major bleeding and five (5%) patients underwent fully matched allogeneic HSCT (hematopoietic stem cell transplant). Graft versus host disease-free relapse-free survival (GRFS) was 80%.

CONCLUSION

GT is still an underrecognized and underdiagnosed disorder, particularly in resource-limited settings where the estimated incidence seems to be much higher than reported.

Novel mutations in Thai patients with glanzmann thrombasthenia

OBJECTIVES

Glanzmann thrombasthenia (GT) is an autosomal recessive platelet disorder, caused by defects of the platelet integrin αIIbβ3 (GPIIb/IIIa) resulting from pathogenic mutations in either ITGA2B or ITGB3. It is characterized by spontaneous mucocutaneous bleeding. The molecular features of GT in Thailand have not been identified. This study aimed to determine the clinical and molecular features of unrelated Thai patients with GT.

METHODS

Four patients with clinically suspected GT were recruited at the Division of Pediatric Hematology/Oncology, King Chulalongkorn Memorial Hospital. The diagnosis was based on clinical and hematological parameters as well as genetic analysis. Whole exome sequencing (WES) was performed in all cases.

RESULTS

Of the four patients studied, the median age at first suspicion of GT was 2.5 years. All presented with severe bleeding symptoms (WHO bleeding scale 3). Flow cytometry to assess the surface GPIIb/IIIa complex showed reduced expression. By WES, we successfully identified seven mutant alleles in ITGA2B. One alteration, the c.2915dup (p.Leu973Alafs*63), was detected in two unrelated families. One patient was homozygous for the c.617T>A (p.Val206Asp). Of the five different mutations, three have never been previously described. These include a missense, c.617T>A (p.Val206Asp), a deletion, c.1524_1533del (p.Gln508Hisfs*3), and a nonsense, c.2344C>T (p.Arg782Ter).

CONCLUSION

This study reported three novel mutations expanding the genotypic spectrum of ITGA2B causing GT.