A collagen- and thrombin-activated (COAT) platelet defect is a platelet function disorder that is due to a reduced ability to generate procoagulant platelets. It is associated with a clinically relevant bleeding phenotype. During physiological platelet activation, a fraction of platelets expresses

phosphatidylserine Phosphatidylserine (abbreviated Ptd-L-Ser or PS) is a phospholipid and is a component of the cell membrane. It plays a key role in cell cycle signaling, specifically in relation to apoptosis. It is a key pathway for viruses to enter cells via a ...

on their surface and become highly efficient in sustaining

thrombin generation Thrombin (, ''fibrinogenase'', ''thrombase'', ''thrombofort'', ''topical'', ''thrombin-C'', ''tropostasin'', ''activated blood-coagulation factor II'', ''blood-coagulation factor IIa'', ''factor IIa'', ''E thrombin'', ''beta-thrombin'', ''gamma- ...

. These so-called COAT platelets, can be generated by dual-agonist stimulation with collagen and thrombin in a laboratory setting. COAT platelet defects should be distinguished from Scott syndrome, a rare

bleeding disorder Coagulopathy (also called a bleeding disorder) is a condition in which the blood's ability to coagulate (form clots) is impaired. This condition can cause a tendency toward prolonged or excessive bleeding (bleeding diathesis), which may occur spo ...

in which patients have impaired phospholipid scrambling and do not express negatively charged phospholipids on their surface even after treatment with calcium ionophores.

References

{{Reflist Rare diseases Syndromes affecting blood Coagulopathies