Fibrinogen Saint-Germain II: hypofibrinogenemia due to heterozygous gamma N345S mutation.

We have identified a novel heterozygous fibrinogen gamma chain mutation, gammaN345S (Fibrinogen Saint-Germain II), in a subject with hypofibrinogenemia. There was no evidence by mass spectrometry of plasma fibrinogen containing the mutant chain. The hypofibrinogenemia was discovered in a 26-year-old man who experienced extensive deep venous thrombosis of the left leg associated with pulmonary embolism. Investigation of potential thromboembolic risk factors revealed heterozygosity of the factor V R506Q mutation (factor V Leiden) and heterozygosity of the prothrombin gene G20210A mutation. The hypofibrinogenemia may be contributory to the thrombophilic manifestations.