Platelet Delta Storage Pool Deficiency In Children : A Case Series

Abstract

Introduction: Delta storage pool deficiency (delta-SPD) is a rare group of platelet disorders characterized by a reduction in the number or content of dense granules which contains ADP, ATP, calcium, histamine and serotonin. delta-SPD causes a mild to moderate bleeding diathesis characterized mainly by mucocutaneous bleeding. A suspected case of delta-SPD is usually diagnosed by the patient's presentation, a family history and suggestive clinical bleeding or preliminary laboratory results such as a typical platelet aggregation pattern, characterized by normal aggregation with ristocetin and lack of second wave of aggregation with ADP or epinephrine. However not all patients have a typical presentation. This is a review of 11 pediatric patients with delta-SPD at our institution. Results: We have 5 males and 6 females with a confirmed diagnosis of delta-SPD. Their current age ranges from 23 months-17 years. 8 are Hispanic, 2 Caucasian and 1 African American. A positive family history of excessive bleeding was obtained in 4 patients. Epistaxis and menorrhagia were the most common presenting symptoms. The youngest patient in the group presented with a subdural hematoma at 2 weeks of age. One of the female patients was previously diagnosed with VWD after presenting with menorrhagia, who was tested for this condition as she had a wet purpura in the mouth. One of the male patients has Noonan's syndrome and another patient had acute lymphoblastic leukemia at the time of this diagnosis. The preliminary work up included a CBC, PT, PTT and Von Willebrand's panel in all patients. PFA was done in 9 patients and reported as abnormal in 3 patients and not accurate in another patient due to platelet clumping. Platelet aggregation study was done in 8 patients and reported as abnormal in 1 patient. The platelet count ranged from 92,000- 552,000/mm3 at diagnosis. Electron microscopy results ranged from 1.24-3.59 dense granule/platelet (normal 4-6 dense granule/platelet). All of the patients were primarily managed by preventive measures and antifibrinolytic agents. Patients with menorrhagia have been managed with hormonal therapy as well. The patient with VWD has been using Stimate and Amicar for control of menorrhagia. Platelet transfusions have been reserved for life threatening bleeds or surgical procedures. Conclusions: The presentation of this rare bleeding disorder is not limited to mucocutaneous bleeding. Presenting symptoms in the very young could be limited to intracranial hemorrhage. Electron microscopy to diagnose this condition should be pursued despite normal platelet function and aggregation studies, especially in patients with a high index of suspicion based on their clinical presentation or family history.