Reduced Number of Dense Bodies and Reduced Serotonin Content in Platelets of Patients with Wiskott-Aldrich Syndrome.

Abstract 1321

Poster Board I-343

Wiskott-Aldrich syndrome is characterized by immune deficiency and thrombocytopenia. There is also a qualitative platelet defect in Wiskott-Aldrich syndrome, typically presenting on aggregometry as a failure of the second wave of aggregation. The pathophysiology of this defect has not been studied in detail. To investigate this phenomenon, we enumerated dense bodies and measured serotonin content in the platelets of 7 patients with Wiskott-Aldrich syndrome. Patients ranged in age from 14 to 45 years old. Five of 7 patients had had splenectomy. In these patients, the platelet count ranged from 120,000/mcL to 521,000/mcL. Platelet counts were 20,000/mcL and 46,000/mcL in the 2 patients who had not had splenectomy. The latter 2 patients had occasional petechiae, as did 2 of the splenectomized patients. Three patients had no clinical evidence of platelet dysfunction. One of these 3 had tolerated abdominal surgery without untoward bleeding. Blood specimens were taken in the course of routine follow-up, when patients were otherwise well. Platelets were prepaed for electron microscopy by the whole mount technique. For serotonin content, platelets were counted and lysed in distilled water. Serotonin in the lysate was chemically acetylated and then measured by ELISA. Serotonin levels were normalized to ng of serotonin per 10 9 platelets. The average ± standard deviation dense body count in our patient group was 1.1 ± 0.4 dense bodies per platelet (normal count 6-8 dense bodies/platelet). Serotonin content was measured in three patients, who showed 273 ± 103 ng serotonin per 10 9 platelets (normal value 621-1064 ng/10 9 platelets). Our results are the first quantitative analysis of platelet dense body counts and serotonin level in patients with Wiskott-Aldrich syndrome. In addition to further elucidating the pathophysiology of this disease, these data have implications for understanding the role of the Wiskott-Aldrich syndrome protein in the genesis of dense bodies.