Abstract • 143

In order to find the genetic risk factors in paediatric patients we analyzed 85 children below 15 years of age with documented thrombosis, observed in the last 5 years. Out of 85 enrolled patients we found only 9 arterial thromboses, most of them in the cerebral district. Out of 76 venous thromboses the localization of thrombotic events was: 12 central nervous system, 23 portal system, 2 renal vein, 9 lower limb veins, 27 associated to CVC, 3 others. Familial history for juvenile thrombotic events and inherited thrombophilic conditions were taken into consideration. Associated conditions were found in 57 (75%) patients. As previously described the presence of CVC is the most important predisposing cause in children. Otitis and meningitis were all present as trigger events in patients with central nervous vein thrombosis. In 3 cases we found Lupus anticoagulant. We tested the biological activity of ATIII, Protein C and Protein S and the molecular defects for APC-r, Ala 223Val MTHFR, G20210A3′ prothrombin gene. We found low levels (-3sd) of ATIII in 5/85 patients, of Protein C in 6/85 patients and of Protein S only in 1 patient out of 57. Factor V Leiden, G20210A prothrombin variant and C677T MTHFR were tested on DNA extracted from peripheral blood samples. We tested about 100 blood donors to calculate the mutation frequency for each gene involved in the healthy Italian population. In our patients the frequency of these mutations does not differ from our control group: C677T MTHFR 14 (16%) vs 16.4%; APC-r 3 (3.5%) vs 4%. The G20210A3′ prothrombin gene seems to be more frequent in patients with thrombosis 5 (5.8%) than in the control population (0.7%). We can conclude that, in children, genetic predisposition alone is not responsible for the thrombotic event. This occurs when inherited and particular acquired risk factors are present.