An intrinsic coagulation pathway inhibitor in a 3-year-old child.

An intrinsic coagulation pathway inhibitor with acitivty against factor XI was detected in the plasma of a 3-year-old child, following a respiratory infection. The inhibitor was present transiently, but it was clinically significant and was manifiested by extensive bruises. Abnormalities of clotting and the bruising tendency disappeared simultaneously without treatment before the inhibitor could be definitively characterized. It was possibly the consequence of an adenovirus infection, as an elevated adenovirus titer was demonstrated in the patient's blood. It is possible that inhibitors of this type are more common sequelae of viral infections than realized, and perhaps a systematic effort should be made to detect them and to define their etiology and mechanism of action.