- Nephrotic syndrome (NS) is associated with an increased incidence of various thromboembolic complications in adult patients. It was found to be due to elevated factor IX (FIX) F.VII, F.VIII, F.V, fibrinogen, thrombocytosis and increased platelet reactivity. Acquired AT-III deficiency, reduced functional levels of protein S and reduced activity of protein C were also reported. We evaluated 15 children aged 1 to 13 years. Thirteen of these children suffered from nephrotic syndrome and two others had non-nephrotic proteinuria. All patients but one were normotensive. Two patients were not steroid responsive. Serum creatinine was normal for age in 14 patients. Kidney biopsy was carried out only in three children. Haemostatic parameters included protein C and S antigenicity in plasma and urine. Plasma levels of protein C and protein S were within the normal range. Protein C antigenicity in urine was increased in five children out of 14 examined. Protein S in urine was increased in seven out of 12 children examined. No thromboembolic phenomena were documented even though protein C and protein S antigenicity were identified in the urine.