Abstract 34

In order to identify the risk factors in paediatric patients we performed a retrospective study on 85 children < 15 years of age, with documented thrombosis, seen in the last 5 years. Familial history, trigger events and inherited thrombophilic conditions were considered. We found only 9/85 cases of arterial thrombosis, most of them in the cerebral district. Out of 76 Venous Thrombosis cases, localization of thrombotic events was: 12 Central Nervous System, 23 portal system, 2 renal vein, 9 lower limb veins, 3 other, 27 (36.5%) cases of thrombosis associated to Central Venous Catheter (CVC). Associated conditions were found in 57 (75%) patients. 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. Data on familiarity are available only in few cases. Out of 58 only 10 parents have familial history in first-degree relatives positive for vascular disease. We did not find any positive familial history in patients with CVC. We tested 85 patients for the most frequent genetic risk factors: MTHFR Prothrombin gene and Factor V Leiden. These mutations were analysed by PCR technique, followed by restriction enzyme digestion. In our patients the frequency of these mutations was: C677MTHFR 14(16%) vs 16.4%; G20210A 3′ UTR Prothrombin gene 5 (5.8%) vs 0.7%; G1691A FV 3 (3.5%) vs 4%. It does not differ statistically from our control population. The natural anticoagulant activity was analysed by chromogenic assay. We found low levels (-3SD) of ATIII in 5/85, of protein C in 6/85 and of Protein S in 1/57. Since this was a retrospective study we could not analyse the patient's parents. The simultaneous presence of one or more risk factors was taken into consideration. We found 39 cases with 1 risk factor, 21 with 2, and 3 with 3 risk factors. Even though we cannot perform any evaluation of incidence, the great number of patients observed in the last years allows us to confirm the importance of thrombosis also in the paediatric age. In children genetic predisposition alone is not sufficient, but thrombosis occurs when one or more inherited or acquired risk factors are present.