Ten Years' Experience with the "Sticky Platelet Syndrome"

Abstract

We describe a 10-year experience with a con genital platelet abnormality characterized by hyperaggre gability with ADP and/or epinephrine. The syndrome has so far been identified in >200 patients and their families. Clinical symptoms are transient or permanent arterial oc clusions, thrombotic in nature, affecting especially the coronary and cerebral vasculature, including ophthalmic vessels. The patients have no identifiable risk factors and are usually young (5-45 years), and other hypercoagula ble states are excluded. In many cases the vascular acci dent is precipitated by severe stressful events. Occasion ally the syndrome is found in patients with recurrent ve nous thromboembolism while they are on optimal oral anticoagulant therapy. In the laboratory the patients' platelets are hyperaggregable with decreasing ADP and/ or epinephrine concentrations added to platelet-rich plasma. Two forms are identified: Type I is marked by hyperaggregability with ADP and epinephrine, while Type II evidences hyperaggregability only with epineph rine. No abnormalities are found when other aggregation stimulators are used. By electron microscopy the plate lets are more readily activated by surface contact, with a greater tendency toward aggregate formation. Plasma lev els of platelet release proteins, platelet factor 4, and β-thromboglobulin are not elevated. The syndrome is treated with low-dose aspirin, which reverses the hyper aggregability and improves clinical symptoms. We hy pothesize that in vivo adrenaline release leads to in creased platelet clumping, which can transiently or per manently occlude small vessels. It is conceivable that altered surface receptors on the platelets might be respon sible for this congenital problem.