[Comparison of coagulation screening test results in two cases having dysfibrinogen]

We compared coagulation screening test [prothrombin time (PT), activated partial prothrombin time (APTT), fibrinogen level determined by thrombin time method] results in two cases of dysfibrinogenemia which were named Matsumoto I (MI) and II (MII), respectively. Amino acid substitution in MI, gamma 364Asp-->His, and that in MII, gamma 308 Asn-->Lys, were deduced by sequencing analysis of PCR amplified products from each genomic DNA. The ratios of functional fibrinogen levels determined by the thrombin time method to immunological levels determined by the latex photometric assay were markedly decreased in both cases. Thrombin time (TT) in the absence of Ca2+ and fibrin aggregation test were also decreased. It was noted that the above described abnormalities were more prominent in MI than MII. We thought these results reflected the extent of abnormality in fibrin monomer polymerization. Furthermore, the mutation at residue gamma 364Asp in MI is adjacent to the gamma 363Tyr which is within the primary polymerization site of fibrin monomer, whereas the mutation at the residue gamma 308Asn in MII is outside the primary site. Since fibrin monomer polymerization is promoted in lower ionic strength and in higher concentration of Ca2+, the data of PT, APTT, and TT, that were tested in the presence of higher concentration of Ca2+ and fibrin monomer, were similar in MI and MII. In addition, it would be speculated that mutant fibrinogen interferes the function of normal fibrinogen existed in heterozygous dysfibrinogenemia.