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Published on: December 27, 2017
Platelet function and bleeding at different phases of childhood immune thrombocytopenia
Anastasia A Ignatova1,2,3, Elena V Suntsova1, Alexey V Pshonkin1
1National Medical Research Center of Pediatric Hematology, Oncology and Immunology Named After Dmitry Rogachev, Russian Ministry of Healthcare, 1 Samory Mashela Str, Moscow, Russia, 117997.
Insights
Platelet size and pre-activation are common in childhood immune thrombocytopenia (ITP). However, increased platelet activation is linked to bleeding only in chronic ITP, suggesting phase-dependent mechanisms.
Area of Science:
- Hematology
- Immunology
- Pediatrics
Background:
- Immune thrombocytopenia (ITP) involves platelet function defects, but mechanisms vary by disease phase, age, and treatment.
- Understanding these differences is crucial for managing pediatric ITP.
Purpose of the Study:
- To investigate platelet function and bleeding in children with acute/persistent and chronic ITP.
- To assess the impact of romiplostim therapy on platelet function in pediatric ITP.
- To differentiate ITP platelet characteristics from other childhood thrombocytopenias.
Main Methods:
- Whole blood flow cytometry was used to analyze platelet size, activation markers (PAC1, CD62p), cytosolic calcium, and procoagulant levels.
- 151 children with ITP (56 acute/persistent, 95 chronic) and 57 healthy controls were studied.
- Non-ITP thrombocytopenia controls included patients with leukemia, aplastic anemia, MYH9-associated thrombocytopenia, and Wiskott-Aldrich syndrome.
Main Results:
- ITP platelets, regardless of phase, were larger and pre-activated (PAC1, CD62p, calcium, procoagulant levels) compared to healthy controls.
- These platelet abnormalities were specific to ITP among childhood thrombocytopenias.
- Higher CD62p expression correlated with bleeding in chronic ITP but not acute/persistent ITP.
- Romiplostim treatment reduced platelet size and CD62p expression, but not cytosolic calcium.
Conclusions:
- Increased platelet size, pre-activation, and cytosolic calcium are characteristic of pediatric ITP.
- The association between platelet pre-activation and bleeding appears dependent on the ITP disease phase.
- These findings highlight distinct platelet behavior in different ITP contexts and treatment responses.
Abstract:
Immune thrombocytopenia (ITP) is believed to be associated with platelet function defects. However, their mechanisms are poorly understood, in particular with regard to differences between ITP phases, patient age, and therapy. We investigated platelet function and bleeding in children with either persistent or chronic ITP, with or without romiplostim therapy. The study included 151 children with ITP, of whom 56 had disease duration less than 12 months (grouped together as acute/persistent) and 95 were chronic. Samples of 57 healthy children were used as controls, while 5 patients with leukemia, 5 with aplastic anemia, 4 with MYH9-associated thrombocytopenia, and 7 with Wiskott-Aldrich syndrome were used as non-ITP thrombocytopenia controls. Whole blood flow cytometry revealed that platelets in both acute/persistent and chronic ITP were increased in size compared with healthy donors. They were also pre-activated as assessed by PAC1, CD62p, cytosolic calcium, and procoagulant platelet levels. This pattern was not observed in other childhood thrombocytopenias. Pre-activation by CD62p was higher in the bleeding group in the chronic ITP cohort only. Romiplostim treatment decreased size and pre-activation of the patient platelets, but not calcium. Our data suggest that increased size, pre-activation, and cytosolic calcium are common for all ITP platelets, but their association with bleeding could depend on the disease phase.
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