A novel missense mutation in the FGB g. 3354 T>A (p. Y41N), fibrinogen Caracas VIII.

A novel dysfibrinogenaemia with a replacement of Tyr by Asn at Bβ41 has been discovered (fibrinogen Caracas VIII). An asymptomatic 39-year-old male was diagnosed as having dysfibrinogenaemia due to a mildly prolonged thrombin time (+ 5.8 seconds); his fibrinogen concentration was in the low normal range, both by Clauss and gravimetric determination, 1.9 g/l and 2.1 g/l, respectively. The plasma polymerization process was slightly impaired, characterised by a mildly prolonged lag time and a slightly increased final turbidity. Permeation through the patients´ clots was dramatically increased, with the Darcy constant around four times greater than that of the control (22 ± 2 x10–9 cm2 compared to 6 ± 0.5 x10–9 cm2 in controls). The plasma fibrin structure of the patient, by scanning electron microscopy, featured a mesh composed of thick fibres (148 ± 50 nm vs. 120 ± 31 nm in controls, p