Structure Abnormality Of Fibrinogen Metz And Its Relationship To The Clotting Defect
Fibrinogen Metz was discovered in a young woman and was associated with a mild bleeding disorder and repeated abortions. Her parents are cousins and both have an abnormal fibrin formation but less intense than in the propositus.Fibrinogen Metz is therefore an homozygous case characterized by an unclottability of citrated sample, even in the presence of calcium and large quantities of thrombin. In addition, the clotting time is prolonged when the blood is collected in the absence of sodium citrate and the clot is extremely weak.By immunoenzymological assay, no release of fibrinopeptide A was noted after thrombin addition to purified fibrinogen. Furthermore, by disc electrophoresis in polyacrylamide gel in absence of SDS, an abnormal migration of the A α chain was observed.These results led us to analyze the sequence of the N terminal part of the A α chain by the Edman procedure. Arginine in position 16 was replaced by cysteine in fibrinogen Metz. This mutation localized on the site cleaved by thrombin explains the absence of fibrinopeptide A release, and the abnormal clottability of fibrinogen Metz.