Antithrombin III (AT III) and fibrinogen levels in nephrotic syndrome in children.

Plasma antithrombin III (AT III) and fibrinogen were measured in 25 Saudi children with nephrotic syndrome during both relapse and remission. During relapse the mean AT III level was 46.6% (range 7-84%) and mean fibrinogen was 992 mg/dl (range 413-1,433), while during remission, AT III levels increased remarkably to a mean value of 120.6% (range 81-160) and plasma fibrinogen dropped to a mean level of 431 mg/dl (range 230-693). In 10 of these patients AT III was measured simultaneously in urine. During relapse urine AT III levels were of the same magnitude as plasma AT III, while during remission no AT III was detected in urine. These findings confirm the hypercoagulable state during the relapse of nephrotic syndrome and the quick recovery during remission. None of our patients showed any clinical evidence of thromboembolism. Loss of AT III in urine during relapse and/or its consumption is the probable cause of low AT III during relapse while excessive production of AT III by liver probably accounts for the high levels in remission.