Development of antibodies to bovine and human factor V in two children after exposure to topical bovine thrombin.

Purpose: Acquired inhibitors to coagulation factors are rare in pediatric patients. Exposure to topical bovine thrombin is a risk factor for the development of inhibitors in adult cardiac surgery patients. We report two pediatric patients who developed inhibitors to bovine and human factor V after exposure to fibrin glue containing bovine thrombin.

Patients and methods: The two patients, ages 3 1/2 years and 10 months, were studied after cardiac surgery. One patient had clinical bleeding. Coagulation factor assays and inhibitor studies were performed.

Results: The presence of a circulating inhibitor to bovine factor V was observed in both patients and to human factor V in one patient. The inhibition of bovine factor V interfered with standard assays for factor VIII activity using a commercial substrate fortified with bovine factor V resulting in spurious factor VIII deficiency. In one patient, an inhibitor of bovine thrombin was also identified. The inhibition of human factor V activity in one patient may have contributed to clinical bleeding.

Conclusions: Pediatric patients exposed to topical bovine thrombin, particularly in the setting of cardiac surgery, are at risk for the development of antibodies to bovine thrombin and factor V. This may also result in apparent but spurious depletion of other coagulation factors. These antibodies may cross-react with human coagulation factors, particularly factor V, resulting in clinical bleeding.