Fibrinogen kaiserslautern III: a new case of congenital dysfibrinogenemia with aalpha 16 arg-->cys substitution.

An abnormal fibrinogen was identified in a man with suspicious prolonged prothrombin time and a mild bleeding tendency. Coagulation studies showed marked prolonged thrombin and reptilase clotting times and a discrepancy between functional fibrinogen test and fibrinogen antigen. The rate of fibrinopeptide B release by thrombin was slightly delayed while the release of fibrinopeptide A was only half the normal amount. DNA sequencing revealed a heterozygous C to T point mutation in position 1202 of exon 2 of the Aalpha chain, resulting in the substitution of Arg-->Cys at position 16, the thrombin cleavage site. This mutation was found also in his 2 children. Both had a mild bleeding tendency too.

Pregnancy-associated risk for venous thromboembolism and pregnancy outcome in women homozygous for factor V Leiden.

INTRODUCTION: To evaluate the pregnancy-associated risk of venous thromboembolism and the risk of stillbirth and miscarriage a multicenter, retrospective and controlled study was conducted in women carrying the homozygous factor V Leiden mutation and in an agematched control group of women from the normal population. PATIENTS AND METHODS: In 64 homozygous (median age 44 years, range 21-75 years) and in 52 control women from five different centers data on venous thromboembolism and pregnancy outcome were obtained. RESULTS: The 64 homozygous women had in total 212 pregnancies, the 52 control women had 118 pregnancies. In homozygous women 65% of pregnancies ended with delivery of a viable infant, 15% with fetal loss (3.3% stillbirth, 12% miscarriage) and 20% by pregnancy termination. In the control women 75% of pregnancies ended with delivery of a viable infant, 12% with fetal loss (1.7% stillbirth, 10% miscarriage) and 13% by pregnancy termination. The differences were statistically not significant. Venous thromboembolism occurred significantly more often in the homozygous women, in 4.2% (9/212) during pregnancy and in 4.7% (10/212) after delivery or pregnancy termination. None of the control women had a thromboembolic episode. CONCLUSION: Our data indicate that women with homozygous factor V Leiden have a high probability for a favorable pregnancy outcome. The increased risk for venous thromboembolism during pregnancy and after delivery would favor heparin prophylaxis during and after pregnancy in women homozygous for factor V Leiden.

First workshop for detection of heparin-induced antibodies: validation of the heparin-induced platelet-activation test (HIPA) in comparison with a PF4/heparin ELISA.

BACKGROUND: No data exist regarding the inter-laboratory reproducibility of the heparin-induced-platelet-activation (HIPA) test, the most widely used functional assay in Germany for the detection of heparin-induced thrombocytopenia (HIT) antibodies. METHODS: Nine laboratories used an identical protocol to test eight different sera with the HIPA test. Five laboratories also tested the sera with a platelet factor 4 (PF4)/heparin-complex ELISA. Cross-reactivity with danaparoid-sodium was assessed using 0.2 aFXa units instead of heparin in the HIPA test. RESULTS: Two of nine laboratories had no discrepant HIPA test results. Four laboratories differed in one sample, one reported two discrepant results, and two laboratories reported more than two discrepant results. Cross-reactivity with danaparoid-sodium test results differed among laboratories. PF4/heparin ELISA results were identical in all five laboratories. CONCLUSION: The HIPA test requires strict quality control measures. Using both a sensitive functional assay (HIPA test) and a PF4/heparin ELISA will allow detection of antibodies directed to antigens other than PF4/heparin complexes as well as detection of IgM and IgA antibodies with PF4/heparin specificity.

Oligosaccharide configuration of fibrinogen Kaiserslautern: electrospray ionisation analysis of intact gamma chains.

Electrospray ionisation mass spectrometry was used to probe the structure of the new N-linked oligosaccharide in fibrinogen Kaiserslautern (gamma 380 Lys-->Asn). The mass increase of 2177 Da in the new beta chain indicated the attachment of a fully sialylated biantennary oligosaccharide on the new Asn residue; the expected increase for this change being 2192 Da. Some 95% of the new oligosaccharide was in the disialylated state while only 5% of the endogenous gamma chain carbohydrate was disialylated in the control. Mass measurements of intact Kaiserslautern gamma chains after neuraminidase treatment of the native fibrinogen confirmed a total of three residues of sialic acid in the dominant isoform. Incubation with endoglycosidase F showed that the new oligosaccharide was more resistant to hydrolysis than the endogenous one. Recent X-ray analyses of covalently linked D domains show that position gamma 380 is distant from both the GPR binding pocket and the D-D interface. It appears that the polymerisation defect of this fibrinogen results from electrostatic repulsion between condensing protofibrils and that this is induced by the two new residues of sialic acid that are present on the new gamma chain.

Fibrinogen Kaiserslautern (gamma 380 Lys to Asn): a new glycosylated fibrinogen variant with delayed polymerization.

An adult woman diagnosed with cerebral thrombosis following a caesarean section was found to have severely prolonged thrombin and reptilase times. Five other family members also had prolonged, but variable, thrombin and reptilase times. Analysis of purified fibrinogen on reducing SDS-PAGE revealed an additional band, in all family members, which migrated immediately below the normal B beta band. Western blotting indicated that this band was a gamma chain and endoglycosidase-F digestion established that it contained an additional oligosaccharide side chain. Partial acid hydrolysis localized the new oligosaccharide to the C-terminus of the gamma chain. Amplification of this region by PCR and subsequent DNA sequencing demonstrated a single base substitution altering the normal 380 Lys (AAG) codon to Asn (AAT), producing a new Asn-Lys-Thr glycosylation site. The propositus and one other family member were homozygous for this mutation but the remaining four family members were heterozygous. The polymerization of purified fibrin monomers from the propositus was grossly abnormal; however, the polymerization curve was almost normalized by the removal of terminal sialic acid residues. This suggests that the polymerization defect was primarily caused by additional negatively charged sialic acid residues present on the new oligosaccharide. Further analysis of the D domain of purified fibrinogen established that calcium binding to the high affinity site remained unaffected by the bulky carbohydrate side chain or negatively charged sialic acid residues.