Fibrinogen Cedar Rapids (g R275C) is a heterozygotic dysfibrinogenemia that is associated with severe pregnancyassociated thrombophilia in three second-generation family members. Like fibrinogen Tokyo II (g R275C) (Mosesson et al, J Clin Invest 1995; 96: ] 053), which is not associated with thrombophilia, fibrinogen Cedar Rapids is characterized by defective fibrin assembly, normal fibrin D:E assembly, and normal fibrinogen and fibrin factor XHIa-mediated crosslinking. Fibrin formed from Cedar Rapids fibrin forms a network structure that is more highly branched than normal fibrin. Investigation of Cedar Rapids family members indicated that each affected subject was also heterozygotic for the factor V Leiden defect. One first-generation parent who was normal with respect to factor V Leiden but expressed the abnormal Cedar Rapids gene, gave no history of thrombophilia, nor did 9 of her siblings. The other parent was normal with respect to fibrinogen Cedar Rapids, but was heterozygotic for the factor V Leiden defect; neither he nor 13 of his siblings gave any history of thrombophilia. One third generation heterozygotic male subject is clinically normal at present but expresses both fibrinogen Cedar Rapids and the factor V Leiden defect. These findings suggest that co-expression of factor V Leiden and fibrinogen Cedar Rapids is causally associated with thrombophilia, although the mechanism by which this situation comes about is not clear.
ASJC Scopus subject areas