Cryoglobulins, Cryofibrinogens, and Cold Agglutinins in Cold Urticaria: Literature Review, Retrospective Patient Analysis, and Observational Study in 49 Patients

Introduction

Cryoproteins, such as cryoglobulins, cryofibrinogens and cold agglutinins, precipitate at low temperatures or agglutinate erythrocytes and dissolve again when warmed. Their pathogenetic and diagnostic importance in cold urticaria (ColdU) is unclear. In this study, we aimed to characterize the prevalence of cryoproteins in patients with ColdU.

Methods

We conducted 3 analyses: i) a systematic review and meta-analysis of published data using an adapted version of the Joanna Briggs Institute's critical appraisal tool for case series, ii) a retrospective analysis of 293 ColdU patients treated at our Urticaria Center of Reference and Excellence (UCARE) from 2014 to 2019, and iii) a prospective observational study, from July 2019 to July 2020, with 49 ColdU patients as defined by the EAACI/GA2LEN/EDF/UNEV consensus recommendations.

Results

Our systematic review identified 14 relevant studies with a total of 1151 ColdU patients. The meta-analyses showed that 3.0% (19/628), 1.1% (4/357) and 0.7% (2/283) of patients had elevated levels of cryoglobulins, cryofibrinogens and cold agglutinins, respectively. Our retrospective analyses showed that cryoproteins were assessed in 4.1% (12/293) of ColdU patients. None of 9 ColdU patients had cryoglobulins, and one of 5 had cold agglutinins. In our prospective study, none of our patients had detectable cryoglobulins (0/48) or cryofibrinogens (0/48), but 4.3% (2/46) of patients had cold agglutinins (without any known underlying autoimmune or hematological disorder).

Conclusion

Our investigation suggests that only very few ColdU patients exhibit cryoproteins and that the pathogenesis of ColdU is driven by other mechanisms, which remain to be identified and characterized in detail.

Cryofibrinogen in patients with hepatitis C virus infection

BACKGROUND

Mixed cryoglobulin is usually associated with hepatitis C virus (HCV) infection and might cause systemic vasculitis. The presence and impact of cryofibrinogen, another cryoprotein, in the serum of HCV-infected patients have not yet been evaluated. The objective was to study the prevalence and the clinical and therapeutic impacts of cryofibrinogen in HCV-infected patients.

METHODS

A total of 143 consecutive HCV-infected (RNA+) patients (including 57 patients with HCV-related vasculitis) were screened for cryofibrinogen and cryoglobulin (positive if >0.05 g/L). The main characteristics and outcome were evaluated according to the cryofibrinogen/cryoglobulin status at baseline.

RESULTS

At baseline, 53 of 143 patients (37%) were cryofibrinogen positive, most of whom (47/53 [89%]) were also cryoglobulin positive. Only 37 of 90 cryofibrinogen-negative patients (41%) were cryoglobulin positive (P<.001). In patients with HCV-related vasculitis, 28 of 57 (49%) were cryofibrinogen positive compared with 25 of 86 patients (29%) without vasculitis (P=.03). There was a higher rate of renal involvement in cryofibrinogen-negative/cryoglobulin-positive patients than in cryofibrinogen-positive/cryoglobulin-positive patients (10/25 [40%] vs 3/27 [11%], respectively; P=.02). After a mean follow-up of 32.6 months, among patients who were cryofibrinogen positive at baseline, 12 of 26 (46%) of those who received an HCV treatment were cryofibrinogen negative at the end of follow-up compared with 4 of 16 (25%) of those who did not receive antiviral drugs. Most patients who became cryofibrinogen negative also became cryoglobulin negative (93%).

CONCLUSION

Cryoproteins, including cryoglobulin and cryofibrinogen, are frequently found in the serum of HCV-infected patients. In such patients, a positive cryofibrinogen status is closely related to the presence of cryoglobulin at baseline and after antiviral therapy.

[Usefulness of a single radial immunodiffusion method for the immediate diagnosis of abnormal fibrinogenemia in the laboratory]

Patients with dysfibrinogenemia demonstrate a low concentration of plasma fibrinogen. However, many cases remain a symptomatic and are incidentally identified on a pre-operative or screening test for pregnancy. Therefore, urgent diagnosis is desirable. To diagnose this abnormality, it is important to demonstrate a discrepancy between test results by the Clauss and immunologic methods. We use a single radial immunodiffusion (SRID) method to measure the fibrinogen level immunologically. We present one dysfibrinogenemia case diagnosed by SRID. The present case was 23 year-old pregnant female. She demonstrated a low plasma level of fibrinogen (91 mg/dl by the Clauss method) on a pre-delivery-screening test in the 39th week of pregnancy. We suspected dysfibrinogenemia, and measured the fibrinogen level immunologically with SRID. Briefly, we dissolved agar in 10% PBS solution and added 1 mg/ml anti-fibrinogen antibody. Then, patient plasma and 50-200 mg/dl of control plasma were placed on the agar overnight. The immunoreactive fibrinogen level in this patient was 400 mg/dl. Therefore, we diagnosed her as dysfibrinogenemia. She did not have a bleeding episode during the normal vaginal delivery even through fibrinogen was not transfused. The SRID method is readily available, and requires only an anti-fibrinogen antibody and agar, both of which are usually stocked by a general laboratory. The practical method and application described in this report provide instructive information for hospital laboratories.

Dysfibrinogen Kagoshima with the amino acid substitution γThr-314 to Ile: Analyses of molecular abnormalities and thrombophilic nature of this abnormal molecule

INTRODUCTION

Emerging lines of evidence have suggested that certain dysfibrinogens present a significant risk of thrombosis.

PATIENT/METHODS

The thrombophilic nature of a new-type of dysfibrinogen Kagoshima identified in a 36-year-old female with deep vein thrombosis during the postpartum period was studied.

RESULTS/DISCUSSION

Based on the analyses of the patient fibrinogen and the fibrinogen genes, fibrinogen Kagoshima was shown to have the amino acid substitution of gammaThr-314 to Ile that resulted in impaired function and hypofibrinogenemia. Polymerization of fibrin monomers derived from patient fibrinogen was severely impaired with a partial correction in the presence of calcium ions, causing very low clottability and delayed cross-linking of patient fibrin catalyzed by activated factor XIII. Because of the low clottability, a large amount of soluble fibrin was formed upon thrombin treatment, resulting in an increase of thrombin in the soluble fraction. Additionally, tPA-mediated plasmin generation on fibrin was impaired and calcium-ion-dependent integrity of the gamma-chain D domain of Kagoshima fibrinogen was perturbed. The presence of many tapered-fiber ends inside the tangled fibrin networks, observed by scanning electron microscopy, suggested early termination of fibrin polymerization and the structural alteration.

CONCLUSION

These data suggest that fibrinogen Kagoshima is dysfunctional, giving rise to formation of fibrinolysis-resistant soluble fibrin polymers and entrance of soluble fibrin associating with thrombin to the circulation, partly accounting for the thrombophilic nature of the affected fibrinogen and fibrin molecules.

Fibrinogen Denver: a dysfibrinogenemia associated with an abnormal Reptilase time and significant bleeding

This paper reports a new dysfibrinogenemia with an unusual pattern of laboratory assays. The patient, a 51-year-old female with a lifelong moderate bleeding history, was initially diagnosed with von Willebrand disease based on routine coagulation assays and the clinical bleeding presentation. During recent testing as part of a preoperative screen and without any current history of treatment, levels of von Willebrand factor (VWF) antigen, VWF activity, and factor VIII activity were all significantly elevated, which was unexpected given her previous diagnosis. Additional testing was performed looking for other heritable causes for her considerable bleeding tendency. Interestingly, the patient had a significantly prolonged Reptilase time, minimally short thrombin time, and an abnormal fibrinogen-crossed immunoelectrophoresis pattern. Clearly, this patient had a fibrinogen abnormality that had been missed when only routine coagulation screening assays were performed. A brief review of the fibrinogen literature revealed no other dysfibrinogenemias reported with a similar pattern of test results, and thus this defect was designated fibrinogen Denver.

Cryofibrinogenemia associated with polyarteritis nodosa

We report the case of a 77-year-old woman with biopsy-confirmed polyarteritis nodosa (PAN) associated with cryofibrinogenemia presenting with polyarthralgia and digital gangrene induced by cold exposure. The clinical manifestations and parameters measured by laboratory markers including cryofibrinogen responded well to corticosteroid therapy. To our knowledge, the case of the combination of PAN and cryofibrinogenemia has not been reported. Our case indicates that cryofibrinogenemia might be associated with PAN. The PAN patients with cold-induced symptoms should be screened for cryofibrinogen.

An approach to the diagnosis and treatment of cryofibrinogenemia

Cryofibrinogenemia is a rarely symptomatic disorder that is underrecognized due to the infrequency with which it causes symptoms. Although completely reversible, this disorder can be life threatening when untreated. In this review, the classification, pathophysiology, and clinical presentation of cryofibrinogenemia are described, based on case reports and prospective observational data. Diagnostic criteria are outlined, and therapies are assessed critically. This information should help clinicians in establishing a diagnosis of cryofibrinogenemia and initiating treatment.

Fibrinogen Magdeburg I: a novel variant of human fibrinogen with an amino acid exchange in the fibrinopeptide A (Aalpha 9, Leu-->Pro)

INTRODUCTION

The exchange of Aalpha 16, Arg for Cys or His is the most common molecular defect in dysfibrinogenemia directly affecting the thrombin cleavage site involved in fibrinopeptide A (FPA) release. Other amino acid exchanges within the fibrinopeptide A have been only rarely reported.

MATERIALS AND METHODS

In clinically asymptomatic dysfibrinogenemic patients with low functional plasma fibrinogen (Fg) levels and prolonged thrombin time but normal or slightly prolonged batroxobin (reptilase) time, mutation analysis was carried out by direct sequencing of the coding regions of the three fibrinogen genes. Isolated fibrinogen was functionally characterized for thrombin- or batroxobin-induced fibrinopeptide release and fibrin formation. Fibrinogen and fibrinopeptides were structurally studied by electrophoretic techniques or high-performance liquid chromatography.

RESULTS AND CONCLUSIONS

Molecular analysis revealed heterozygosity for a novel missense mutation T1182C in the FGA gene causing the amino acid exchange Aalpha 9, Leu-->Pro. Fibrin generation induced by thrombin was moderately impaired, whereas batroxobin-induced fibrin formation was almost normal. Release of the abnormal fibrinopeptide A by thrombin was delayed but fibrin monomer aggregation was almost normal. Cleavage of Aalpha chains by batroxobin was only slightly delayed. Fibrinopeptides A of the patient fibrinogen did not show any gross abnormality in chromatographic behaviour. This new molecular variant designated fibrinogen Magdeburg I supports the view that amino acid residue Leu-9 in the Aalpha chain as part of a small hydrophobic cluster is involved in the interaction with an apolar binding site of thrombin, thus adding to our understanding of the thrombin-fibrinogen interaction crucial in coagulation.

[Role of newly developed technology in blood coagulation disorders]

Clarification of blood coagulation disorders has been made progress based on newly developed technologies. ANTITHROMBIN III: In 1979, studies were carried out on antithrombin III(AT III) as a blood coagulation inhibitor from the first Japanese case of congenital AT III deficiency found in the laboratory sample. An alternative anticoagulant to maintain fluidity in extracorporeal circuit in an AT III deficient patient requiring hemodialysis was needed. In 1989, it was firstly introduced argatroban, a synthetic thrombin inhibitor as an alternative anticoagulant instead of human antithrombin III concentrate plus heparin regimen during hemodialysis. In 1992, success of good delivery in pregnant woman with an AT III deficiency was obtained to maintain normal level of AT III by the concentrates. DYSFIBRINOGENEMIA: Two families of congenital dysfibrinogenemia in clue to abnormally high levels of serum fibrinogen degradation products(FDP) were found. Polymerization detect due to dysfibrinogenemia induced high level of serum FDP and normal level of fibrin d-dimer products. HEPARIN COFACTOR II DEFICIENCY: A patient with congenital heparin cofactor II(HCII) deficiency was found in clue to four episodes of repeated restenosis under heparin-anticoagulated coronary angioplasty. For preventing the restenosis, argatroban as an alternative of heparin was used during coronary angioplasty. No restenosis after the angioplasty was appeared in anticoagulation with argatroban. Genetic analysis of the HCII was described that gene protein is secreted normally, but rapidly degraded in the circulation. FACTOR VII: In Japanese elderly, increase of Factor VII clotting activity was found to relate to high risk of cardiovascular disease. Elevation of activated FVII(FVIIa) as an activation marker of FVII in cardiovascular disease indicates to be an independent risk factor for cardiovascular disease. HEPARIN INDUCED THROMBOCYTOPENIA: HIT: HIT is believed to be less frequent in Japanese because of lack of recognition due to poor understanding of HIT's paradox. A survey in Japanese indicated to be no less frequent compared with that of the West. A causativity for HIT has been identified as antibodies against PF4/heparin complexes. As detection of the antibodies can easily be done by ELISA test, the test is desirable to become popular. Treatment for HIT is recommended to stop heparin and start a thrombin inhibitor. In Japan, argatroban and nafamostat mesilate are selected as an alternative agent for HIT, but both drugs have no approval for Japanese HIT patients.

Three new cases of dysfibrinogenemia: Poissy III, Saint-Germain I and Tahiti

In order to identify unknown mutations, the FAMA method was used to rapidly screen the fibrinogen chain genes in individuals with dysfibrinogenemias. Chemical cleavage at mismatches on heteroduplexes DNA end-labeled with strand-specific fluorescent dyes reliably detects sequence changes in DNA fragments of up to 1.5 kb and locates them precisely. This method was successfully used for the detection of three new dysfibrinogenemias: Poissy III, Tahiti (heterozygous Aalpha Arg16His) and Saint-Germain I (heterozygous AalphaGly12Val). The mutations were confirmed by dideoxy sequencing.

Cryofibrinogenaemia: a study of 49 patients

The purpose of this study was to characterize the clinical features and components of 30 patients with isolated cryofibrinogen (CF) versus those of 19 patients with combined CF and cryoglobulins (CG). Secondary forms of cryofibrinogenaemia associated with collagen disorders, infectious or malignant diseases, were significantly more frequent in patients with combined CF and CG than those with isolated CF (79 versus 47%, P = 0.02). Both groups of CF patients presented predominantly cutaneous symptoms (77% in isolated CF; 58% in combined CF + CG), and less frequently venous and/or arterial thrombosis (13% in isolated CF; 3% in combined CF + CG). Patients with idiopathic forms of CF, and particularly those without CG, suffered essentially from recurrent painful skin ulcers, mainly triggered by cold exposure. Patients with isolated CF had higher mean plasma concentrations of CF than those with combined CF + CG (1. 61 +/- 1.26 versus 0.82 +/- 1.18 g/l, respectively; P = 0.004), but there was no correlation between the CF plasma level and either the severity of symptoms or the sensitivity to cold. In patients with isolated CF, fibronectin was suggested (by precipitation analysis) to be a major component of the cryoprecipitate, whereas immunoglobulins were rarely present (in only three out of 30 patients). By contrast, in the majority of patients (78%) with combined CF and CG, the CF consisted mainly of immunoglobulins of the same class as those characterizing the associated CG. Analysis of the CG precipitate revealed the presence of fibronectin but not fibrinogen, alpha1-antitrypsin and alpha2-macroglobulin. In conclusion, isolated and combined cryofibrinogenaemia are associated with different clinical signs requiring different clinical management, but there is no evidence as yet for a causal role of the cryoprecipitates in the differences observed.

Familial primary cryofibrinogenemia

BACKGROUND

To our best knowledge this is the second case ever described of familial primary cryofibrinogenemia (CFG).

PATIENTS

A 29-year-old Moroccan female and two of her three children suffered from painful purpura, slow healing small ulcerations and edema of both feet during the winter season. Laboratory investigations revealed the presence of cryofibrinogen in their blood plasma. All three patients were otherwise healthy and no associated disease could be demonstrated.

CONCLUSIONS

The diagnosis of CFG has to be considered in patients with livedo reticularis, edema, painful purpura and slow healing ulcera after cold exposure. Cryofibrinogen-precipitates in the blood plasma have to be determined. Because secondary CFG occurs much more frequently than the primary form, it is important to rule out associated diseases through extensive physical examination and laboratory investigations. This communication also stresses the importance of a through family history of patients with CFG. An autosomal dominant mode of inheritance is supposed.

Central retinal vein occlusion associated with cryofibrinogenemia in a young adult--study of skin dynamic capillaroscopy

A 26-year-old woman presented with a 2-month history of intermittent dim vision in her right eye and a diagnosis of central retinal vein occlusion (CRVO) was made. Investigations revealed Raynaud's phenomenon and cryofibrinogenemia. Skin capillaroscopy revealed tortuous vessels and decreased capillary blood-cell velocity in the capillaries of her finger nail fold which coincided with the CRVO attack. After treatment with oral aspirin for 3 months, the CRVO subsided, the capillary blood-cell velocity in the nail fold improved, and serum cryofibrinogen was undetectable. The time course of the cryofibrinogenemia and skin capillaroscopic findings correlated well with her ocular presentations. Study of cryofibrinogen should be included in the evaluation of young adults with CRVO.

[Investigational and methodological difficulties in the demonstration of cryoglobulins]

Cryoglobulins and cryofibrinogens are special forms of cryopathies. With regard to the clinical findings, determination and analysis of cryoproteins can support the diagnostics. Because cryoproteins occur in patients and healthy persons, occasionally it may be difficult to estimate the clinical significance. We determined and analyzed cryproteins in 47 patients with the following diagnoses: urticaria (8), morbus Raynaud (10), acrocyanosis (7), vasculitis (3), collagenosis (6), lupus erythematosus (2), suspect of cryoproteinemia (9) and of cryofibrinogenemia (2). There were cryoproteins in 42 patients of the following characteristics: immunoglobulins A, G, M (14), fibrinogen (2), immunoglobulins A, G, M together with fibrinogen (26) with a considerable predominance of IgM. There was no correlation between the diagnoses and the cryoprotein types, and therefore it is reasonable to determine cryoproteins in close cooperation with the clinics. Contamination of the cryoprecipitates with hemoglobin from red blood cells can simulate alpha 2-macroglobulin and cause misinterpretations.

Congenital dysfibrinogenemia

Fibrinogen abnormalities can be classified as congenital or acquired. Each class manifests quantitative or qualitative alterations; the latter are known as dysfibrinogenemias. In dysfibrinogenemias, structural defects cause alterations in the conversion of fibrinogen to fibrin. Approximately 300 abnormal fibrinogens have been reported, and about 83 structural defects have been identified. The most common structural defect involve the fibrinopeptides and their cleavage sites, and the second most common involves the gamma-chain polymerization region. Approximately half of the mutants are clinically silent, whereas hemorrhage and thrombosis occur in almost equal numbers of cases. Study of the abnormal fibrinogens has provided insight into fibrinogen structure and fibrin formation and dissolution. Some of the structural abnormalities exhibit defective assembly and activation of components of the fibrinolytic system on the abnormal fibrin, resulting in impaired dissolution of fibrin, clinically associated with thrombosis.

[Transient dysfibrinogenemia and thrombocytopenia associated with recurrent acute pancreatitis in the course of isotretinoin therapy]

A 17 year-old young man developed two episodes of acute pancreatitis, separated by a 2 year interval and associated with isotretinoin therapy. In 1989, vesicular sludge without lithiasis was evidenced and in 1991, gall bladder stones were found by cholecystectomy. Concomitantly, transient dysfibrinogenemia and thrombopenia were present. It is interesting to note that far away from the use of isotretinoin, the patient suffered from another episode of acute pancreatitis without any coagulation disorder. The involvement of Roaccutane in cellular differentiation is discussed as well as its causal association with acquired dysfibrinogenemia and transient thrombocytopenia.

[The influence of certain biochemical plasma factors on the rheological properties of white blood cells in acute cerebral ischemia]

Basing on the analysis of correlations between the rheological properties of white blood cells and certain biochemical plasma factors, in a group of 12 patients with acute ischaemic stroke, a positive correlation (p < 0.05) between the level of fibrinogen and the value of the relative filtration rate was determined. The result indicates that fibrinogen plays a role as a one of the factors decreasing white blood cell elasticity in the acute cerebral ischaemia.

Molecular basis of fibrinogen Naples associated with defective thrombin binding and thrombophilia. Homozygous substitution of B beta 68 Ala----Thr

In an abnormal fibrinogen (fibrinogen Naples) associated with congenital thrombophilia we have identified a single base substitution (G----A) in the B beta chain gene that results in an amino acid substitution of alanine by threonine at position 68 in the B beta chain of fibrinogen. The propositus and two siblings were found to be homozygous for the mutation, whereas the parents and another sibling were found to be heterozygous. Individuals homozygous for the defect had a severe history of both arterial and venous thrombosis; heterozygous individuals had no clinical symptoms. The three homozygotes had a prolonged thrombin clotting time in plasma, whereas the heterozygotes had a normal thrombin clotting time. Fibrinopeptide A and B (FpA and FpB) release from purified fibrinogen by human alpha-thrombin was delayed in both the homozygous propositus and a heterozygous family member. Release of FpA from the normal and abnormal amino-terminal disulfide knot (NDSK) corresponded to that found with the intact fibrinogens, indicating a decreased interaction of thrombin with the NDSK part of fibrinogen Naples. Binding studies showed that fibrin from homozygous abnormal fibrinogen bound less than 10% of active site inhibited alpha-thrombin as compared with normal fibrin, while fibrin formed from heterozygous abnormal fibrinogen bound approximately 50% of alpha-thrombin. These results suggest that the mutation of B beta Ala 68----Thr affects the binding of alpha-thrombin to fibrin, and that defective binding results in a decreased release of FpA and FpB in both homozygous and heterozygous abnormal fibrinogens.

Fibrinogen Lima: a homozygous dysfibrinogen with an A alpha-arginine-141 to serine substitution associated with extra N-glycosylation at A alpha-asparagine-139. Impaired fibrin gel formation but normal fibrin-facilitated plasminogen activation catalyzed by tissue-type plasminogen activator

An A alpha-arginine-141 to serine substitution has been identified in a homozygous dysfibrinogen, fibrinogen Lima, associated with impaired fibrin polymerization. The point mutation created an asparagine-X-serine-type glycosylation sequence, and indeed, extra, mainly disialylated biantennary oligosaccharides have been isolated from A alpha asparagine-139 of the patient's fibrinogen. This type of glycosylation sequence is unique for human fibrinogen, because the sequences shown for normal and abnormal fibrinogens are all asparagine-X-threonine types. The terminal sialic acids of the extra oligosaccharides seem to have largely contributed to the impaired fibrin gel formation, as evidenced by its correction to a near normal level by desialylation. Nevertheless, the polymerizing fibrin facilitated tissue-type plasminogen activator-catalyzed plasmin formation in a normal fashion, indicating that the initial two-stranded fibrin protofibrils had been constructed normally. Thus the impaired fibrin gel formation could be attributed to the delay in their subsequent lateral association, most probably because of the repulsive forces generated by the negative electric charge of the extra sialic acids. The substitution of a basic residue arginine to a noncharged residue serine may also have contributed to the impaired function in a similar manner or by steric hindrance in association with bulky extra oligosaccharide chains.

Severe congenital dysfibrinogenemia (fibrinogen-Riyadh): a family study

Congenital severe dysfibrinogenemia was discovered in a small Saudi family. Their single child exhibited abnormal severe bleeding tendency since birth and his coagulation profile revealed evidence of severe dysfibrinogenemia. The parents who were first-degree cousins and completely asymptomatic showed evidence of dysfibrinogenemia but to lesser degree than in their son. The child presented with large cephalohematoma and evidence of intracranial hemorrhage and left hemiparesis. He was treated with cryoprecipitate and his hematoma resolved, but his neurological deficit remained.

Fibrinogen Kyoto II, a new congenitally abnormal molecule, characterized by the replacement of A alpha proline-18 by leucine

A new case of heterozygous dysfibrinogenemia characterized by an amino acid replacement in the NH2-terminal region of the fibrin alpha-chain was found in a 27-year-old woman with a bleeding problem. Her one-stage prothrombin time and activated partial thromboplastin time were slightly prolonged, and the purified fibrinogen from this patient had a markedly prolonged thrombin or reptilase time. Release of fibrinopeptides A and B was normal, but the polymerization of fibrin monomers was impaired. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified fibrinogen under the reduced condition showed no abnormalities in the apparent molecular weights of its three chains. Reverse-phase high performance liquid chromatography (HPLC) of the lysylendopeptidase-cleaved purified A alpha-chains showed a decrease in one peptide compared with the normal amount and the appearance of an abnormal peptide peak. These peptides were treated with thrombin and further separated on HPLC. Amino acid sequence analysis of the abnormal peptide indicated that A alpha proline-18, the second residue from the NH2-terminus of the fibrin alpha-chain, was replaced by leucine. The synthetic peptide Gly-Pro-Arg-Pro inhibited both thrombin- and reptilase-induced fibrin aggregation, but Gly-Leu-Arg-Pro showed little or no inhibition under the same conditions. The discovery of this abnormal fibrinogen supports the findings that A alpha proline-18 is important as part of the polymerization site in the NH2-terminus of the fibrin alpha-chain. The propositus' mother had the same abnormal fibrinogen. This unique inherited abnormal fibrinogen was designated as fibrinogen Kyoto II.

Polymerization defect of fibrinogen Baltimore III due to a gamma Asn308----Ile mutation

Fibrinogen Baltimore III, a congenital abnormal fibrinogen with impaired fibrin monomer polymerization, displays a normal gamma-chain and a gamma-variant that has an apparently lower relative molecular weight (mol wt) than normal on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Reverse phase high-performance liquid chromatography (HPLC) analysis of the lysyl endopeptidase digest of the purified gamma-chains of fibrinogen Baltimore III revealed the presence of a peptide that is not found in the digest of the normal fibrinogen gamma-chain. Amino acid sequence analysis of this peptide indicated that the gamma-chain residue 308, asparagine, is replaced by isoleucine. Concanavalin A bound both normal and variant gamma-chains of fibrinogen Baltimore III, indicating that the carbohydrate moiety is not altered and is not responsible for the increase in electrophoretic mobility of the Baltimore III gamma-chain. This study suggests that the integrity of gamma Asn308 is critical for fibrin monomer polymerization, since alteration to either a basic (fibrinogen Kyoto I, Asn----Lys) or hydrophobic (Asn----Ile) residue results in significantly delayed polymerization of fibrinogen to fibrin.

Fibrinogen Sevilla, a congenital dysfibrinogenemia characterized by an abnormal monomer aggregation and a defective plasmin lysis

A dysfibrinogenemia (fibrinogen Sevilla) was detected in a 64-yr-old woman with no previous history of hemorrhagic diathesis or thrombosis. Thrombin and reptilase times were prolonged. The aggregation of fibrin monomers showed a prolonged latency time with a defective slope although fibrinopeptide release and clot stabilization were found to be normal. Plasmin proteolysis was abnormal with a much slower plasmic degradation in patient's purified fibrinogen. By chromatofocussing the patient's fibrinogen showed an abnormality in pattern elution with a second peak eluting at a pH slightly more basic than the normal one (pH 5.5). Likewise, the isoelectrofocussing of purified non-reduced patient's fibrinogen in agarose gel showed an abnormal distribution in its focussed bands, especially in a group which focussed in a pI-interval between 5.20-5.85. By two-dimensional electrophoresis we did not find any abnormality in the fibrinogen-reduced chains. These results could indicate that the abnormal monomer aggregation, as well as the defective plasmin lysis, could be due to conformational aspects of fibrinogen rather than to structural defects.