Abnormal function of fibrinogen was observed in a 2 5-year-old woman with no symptoms attributable to dysfibrinogenemia. Disturbed polymerization of fibrin monomer was identified, but the release of fibrinopeptide from the purified fibrinogen and the cross-linking by factor XIII were normal. Other abnormal findings included a high value of fibrinogen degradation products, rapid mobility on immunoelectrophoresis and abnormal spot of γ-chain on two-dimensional polyacrylamide gel electrophoresis. Similar abnormalities were also observed among the patient’s family membe