Hemostasis in Glanzmann's thrombasthenia (GT): GT platelets interfere with the aggregation of normal platelets.

The transfusion requirements for a 6-year-old Glanzmann's thrombasthenia (GT) patient undergoing tonsillectomy and adenoidectomy were studied. Transfusion of pheresed platelets from a single normal donor increased the platelet count by 63 x 10(9)/L but did not correct the bleeding time. Since the ratio of normal:GT platelets in vivo was approximately 1:5, it was possible that GT platelets interfered with the function of normal platelets. To test this hypothesis, mixtures of platelet-rich plasma (PRP) from a normal donor and the patient were studied to determine a ratio of normal:GT platelets that would yield acceptable in vitro aggregation. Normal:GT ratios of 1:4 and 3:2 resulted in 25% and 59% aggregation, respectively. Mixtures of normal and nonfunctional ethylene glycol tetra-acetic acid-treated platelets gave similar results. Aggregates from mixtures of normal and patient platelets were also examined morphologically by light microscopy and were proportional in size to the normal:GT platelet ratio. Transfusion of platelets from the pheresis of four donors increased the patient's platelet count by greater than 300 x 10(9)/L (normal:GT ratio 1:1), produced 53% aggregation, and resulted in satisfactory postoperative hemostasis. The platelet transfusion requirement for this GT patient was much greater than would have been expected in the absence of aggregation-defective platelets.