Idiopathic autoantibody that inhibits fibrin monomer polymerization

A 73-year-old female was found to have prolonged thrombin and reptilase times in the immediate post-operative period. These abnormalities were not corrected by the addition of normal plasma. They were subsequently shown to be due to an IgG immunoglobulin which inhibited fibrin monomer polymerization. The IgG immunoglobulin activity could be neutralized completely by prior incubation with either patient or normal fibrinogen, uncrosslinked fibrin monomers or IgG antisera. No inhibitory effect on thrombin activity, fibrinopeptide A release or on the fibrin cross-linking reaction of factor XIIIa could be detected. Purified patient fibrinogen was functionally normal as demonstrated by normal fibrinogen-fibrin polymerization and fibrinopeptide A release. No underlying cause for this phenomenon was found. The presence of the inhibitor was associated with excessive blood loss during the post-operative period.