Inhibitor to factor V in severe factor V congenital deficiency. A case report.

A case of severe factor V deficiency that developed an inhibitor to factor V following the treatment with fresh frozen plasma (FFP) is described. The patient had a CRM-negative form of factor V congenital deficiency: no factor V antigen could be assayed in her plasma. A sister who supposedly had a severe factor V deficiency died as a result of a severe posttransfusional hepatitis. Two other members of the family were found to be heterozygotes. After several exposures to FFP, the propositus became refractory to the treatment with the appearance of a low titre inhibitor (5 units) which, nevertheless, could not be overcome by plasma infusions.