Specifities of the storage pool and morphology of platelets in children with unspecified hemorrhagic syndrome

Abstract

Despite modern possibilities of laboratory diagnosis of hemorrhagic syndrome, in some patients, the causes of bleeding remain unspecified. Among these reasons, mild defects in the platelet link of hemostasis can potentially be hidden. The aim of the work is to identify the features of the function of the platelet hemostasis in children with unspecified hemorrhagic syndrome. This study is supported by the Independent Ethics Committee and approved by the Academic Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. We examined 50 patients aged 2 to 17 years with various manifestations of bleeding and lack of laboratory data proving coagulopathy and/or thrombocytopenia; platelet cytofluorometry with activation was performed. The morphological characteristics of platelets in terms of size/granularity (FSC/SSC), the density of the CD62p receptor as a marker of a-granule secretion, and d-granules of platelets were assessed by the fluorescence of loaded mepacrine. Platelet activation was performed with a CRP + TRAP mixture. Comparison was carried out with the results of examination of 50 healthy children (control group - CG) aged 2 to 17 years. The severity of hemorrhagic syndrome was assessed using the standardized ISTH BAT score. The severity of hemorrhagic manifestations according to BAT ISTH score ranged from 2 to 6 points. As a result of the study, two groups of patients differing in the calculated parameter of the FSC/SSC ratio for non-activated platelets were identified. In the CG, the median FSC/SSC was 1.235 (from 1.1 to 1.4), in group 1 (n = 19), the median was 0.97 (from 0.9 to 1.05), and in group 2 (n = 31), the median was 1.24 (from 1.11 to 1.43). The number of platelets of the CG and the groups of patients did not differ significantly. A significant correlation between a decrease in the number of platelets and an increase in their size and granularity, while maintaining a high correlation between size and granularity was observed in groups of patients. In group 1, the overall granularity was increased regardless of the size and number of platelets, the volume of dense granules and membrane CD62p was increased, but the granular CD62p was decreased. The degranulation mechanism was not impaired in both groups of patients. Our results indicate convincingly the contribution of the storage pool and platelet morphology disorders to the development of hemorrhagic manifestations in children with unspecified hemorrhagic syndrome.