Haemostasis alterations in immune thrombocytopenia and their clinical significance.

Immune thrombocytopenia (ITP) is highly heterogeneous, and only a subset of patients with severe thrombocytopenia develops significant bleeding. ITP is also associated with a paradoxical increased risk of thrombosis. Here, we review the multiple haemostasis alterations reported in patients with ITP. Data show an increased platelet basal activation with lower platelet reactivity but with overall increased platelet function. The activated state of platelets and the endothelial dysfunction lead to an activation of coagulation. These alterations tend to counterbalance the bleeding tendency related to thrombocytopenia but have some variability among patients. Consequently, several functional assays have correlated the magnitude of haemostasis alterations to bleeding risk. These results suggest that ITP is a multifaceted bleeding disorder that goes beyond simple thrombocytopenia. The heterogeneity in the various alterations in haemostatic function is likely to drive the variable bleeding phenotypes observed. Haemostasis functional assays could thus serve as clinically relevant tools to individualize management.