Summary
Prothrombin fragment 1+2 (F1+2) and thrombin-antithrombin complexes (TAT), as well as other coagulation and fibrinolysis
parameters, were studied in a series of 13 patients affected by thrombotic thrombocytopenic
purpura (TTP) or hemolytic-uremic syndrome (HUS). Fragment F1+2 was found to be increased in all patients at diagnosis (patients' range, 1.21-19.03
nmol/1; normal limits, 0.28-1.08 nmol/1), and remained also higher than normal after
treatment with plasma exchange (patients' range, 1.5-4.01 nmol/1). Even though the
analysis of fibrinolysis markers did not show a definite state of hypo or hyperfibrinolysis
in the systemic circulation, enhanced circulating D-dimer levels (0.53-12.6 ug/ml,
normal levels of 0.03-0.29 εg/ml) indicated that a certain grade of fibrin lysis was
present at previously formed thrombi. Plasma PAI-1 activities either on admission
(9.2-38.2 U/ml) and after plasma exchange therapy (2.6-38.6 U/ml) showed a behavior
irrespective of t-PA: Ag changes, and post-plasmapheresis values remained high only
in patients with fatal neurological outcome. Nevertheless, no correlations between
clinical and laboratory data could be established useful for the TTP/HUS prognosis.
We conclude that increased thrombin generation occurring in damaged areas is appropriately
inhibited by antithrombin III in the systemic circulation, avoiding consumption coagulopathy
to develop in uncomplicated patients. In addition, fibrinolysis data suggest that
elevated PAI-1 may decisively favor the development of microvascular thrombi.
