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

Guideline for diagnosis and management of congenital dysfibrinogenemia

INTRODUCTION

Congenital dysfibrinogenemia (CD) is characterized by dysfunction induced by an abnormal fibrinogen molecule structure that results in blood coagulation dysfunction. The clinical manifestations of CD patients are asymptomatic, bleeding and thrombosis. The majority of patient are asymptomatic. However, the single fibrinogen detection method is easy to cause missed diagnosis or misdiagnosis of CD patients. The treatment strategies of CD patients with different clinical manifestations are also different.

METHODS

Combing the existing experimental diagnosis technology, literature and our research results, a simple and practical CD diagnostic criteria was proposed. And based on the relevant literature and existing treatment guidelines, more comprehensive treatment recommendations are summarized.

RESULTS

In this new criteria, combination Clauss method and PT derived method was proposed to detect fibrinogen and its ratio was used to diagnose for CD. Diagnosis also needs to be combined the clinical manifestations, family investigation and genetic testing. According to different clinical manifestation (bleeding, thrombosis or asymptomatic), treatment methods and strategies are different. The treatment of CD patients should consider the patient's personal and family history of bleeding or thrombosis. Treatment of thrombosis and pregnancy may be more challenging. The risk of bleeding and thrombosis should be evaluated and balanced at all times during clinical treatment. These detailed treatment recommendations can provide reference for patients with different clinical manifestations of CD.

CONCLUSIONS

The new CD diagnosis criteria and comprehensive treatment recommendations can effectively improve the diagnosis and treatment of CD.

A novel fibrinogen variant: dysfibrinogenemia associated with γAsp185Asn substitution

To identify the pathogenesis of a Chinese woman diagnosed with dysfibrinogenemia. A patient from Nanjing presented with a low plasma concentration of fibrinogen and a normal level of antigen of fibrinogen. This abnormality was also detected in her son. To detect whether the genetic mutation was responsible for the dysfibrinogenemia, genomic DNA was extracted and amplified by polymerase chain reaction, and DNA sequencing was performed on the purified PCR products. Restriction fragment length polymorphism (RFLP), molecular modeling and homologous sequences alignment were performed. Two heterozygous missense variants, AαArg16His and γAsp185Asn, were discovered in the proband. Only the former was detected in her son. AαArg16His had been reported by other teams, and γAsp185Asn was identified first in our study as a novel variant. RFLP was performed and indicated that the novel failed to be found in normal subjects. Furthermore, it was suggested to be responsible for dysfibrinogenemia depending on the molecular modeling and homologous sequence alignment. The heterozygous AαArg16His and γAsp185Asn identified in the study probably underlie the dysfibrinogenemia in this pedigree, with the latter being identified for the first time.

Three cases of congenital dysfibrinogenemia in unrelated Chinese families: heterozygous missense mutation in fibrinogen alpha chain Argl6His

Congenital dysfibrinogenemia (CD) is a qualitative fibrinogen disorder caused by an abnormal fibrinogen molecule structure, leading to dysfunctional blood coagulation. This study describes 3 cases of dysfibrinogenemia identified in the unrelated Chinese pedigrees.Routine coagulation screening tests were performed on the probands and their families. The antigens and functionality of fibrinogen was measured using an immunoturbidimetry assay and the Clauss method, respectively. To identify the genetic mutation responsible for these dysfibrinogens, genomic DNA extracted from the blood was analyzed using PCR amplification and direct sequencing. The presence of the mutant chains was determined using matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectroscopy. Purified plasma fibrinogen of 3 probands was analyzed using SDS-PAGE, fibrinogen clottability, fibrin polymerization, fibrinopeptide release, and scanning electron microscopy (SEM).The 3 probands had a long thrombin time. Levels of functional fibrinogen were found to be very low, while the fibrinogen antigen was within the normal range. DNA sequencing revealed a heterozygous Arg16His substitution in the fibrinogen Aα chain (FGA). The mutant chains were found to be expressed using MALDI-TOF mass spectroscopy. SDS-PAGE did not reveal any difference in the molecular weights of 3 polypeptide chains between normal and abnormal fibrinogens. Fibrinogen clottability showed a slower fibrin clot formation than the healthy control. Fibrin polymerization, after addition of thrombin, showed a prolonged lag phase and decreased final turbidity. The kinetics of fibrinopeptides release revealed a decreased amount of the released fibrinopeptide A. SEM of the patient's fibrin clot was found to be abnormal.Results indicate that the 3 probands with dysfibrinogenemia were caused by mutations of Aα chain Arg16His. Mutation of this fibrinogen induced dysfunction of plasma fibrinogen.

Clinical phenotype, laboratory features and genotype of 35 patients with heritable dysfibrinogenaemia

Heritable dysfibrinogenaemia (HD) is a rare qualitative disorder of fibrinogen (FGN). To better describe the clinical, laboratory and genotypic spectrum of HD, we evaluated 35 subjects identified at two UK centres using laboratory criteria. 12/35(34%) subjects with HD experienced bleeding (bleeding score >1 at any site), 3/35(9%) thrombosis and 20/35(57%) were asymptomatic. Amongst subjects with bleeding, symptoms were typically mild, at one anatomical site and seldom occurred after invasive procedures. All subject showed dry clot weight within or above laboratory reference interval (median 3·2 g/l; range 1·9-5·1), reduced Clauss fibrinogen (median 0·52 g/l; range 0·21-1·3), and prolonged thrombin (median 30·7 s; range 21·3-45·7) and reptilase (median 42·0 s; range 20·0-68·0) times. In all subjects, the prothrombin time ratio (PTR), determined by Sysmex CA-1500 coagulometer and Innovin activator, was abnormal (median 1·42; range 1·22-1·61). The activated partial thromboplastin time ratio and PTR with other coagulometers and activators were comparatively insensitive to HD. All subjects with HD harboured heterozygous candidate nucleotide variations within known hotspots in the FGN genes. The HD variants identified in this cross-sectional study seldom have significant clinical manifestations and show similar laboratory features irrespective of genotype. Selection of coagulometer and PT activator may markedly affect the detection of new HD cases using coagulation screening tests.

Fibrinogen Nový Jičín and Praha II: Cases of hereditary Aα 16 Arg→Cys and Aα 16 Arg→His dysfibrinogenemia

INTRODUCTION

Various dysfibrinogenemias have been described worldwide. This paper describes two new cases of dysfibrinogenemia identified in the Czech Republic.

MATERIALS AND METHODS

The proposita of fibrinogen Nový Jicín, a 12-year-old girl, presented with hemorrhagic complications, low Clauss fibrinogen level (0.3 g/l) and prolonged both thrombin (70.8 s) and reptilase (>180 s) time. Her mother and sister both presented with normal coagulation tests, normal fibrinogen level and reported no history of bleeding. The carriers of the fibrinogen Praha II were a 31-year-old man and his 11-year-old daughter. They both presented with low fibrinogen Clauss level (0.88 g/l) and prolonged thrombin and reptilase time. To identify the genetic mutation responsible for these dysfibrinogens, genomic DNA extracted from the blood was analyzed. The presence of the mutant chains in the circulation was determined by MALDI-TOF mass spectroscopy. Scanning electron micrographs of the patients' fibrin clots were obtained.

RESULTS

The kinetics of fibrinopeptide release and fibrin polymerization were impaired for both fibrinogen Nový Jicín and Praha II. DNA sequencing showed heterogeneous fibrinogen Aalpha R16C mutation in the fibrinogen Nový Jicín case and heterogeneous fibrinogen Aalpha R16H in the fibrinogen Praha II case. The mutant chains were found to be expressed to the circulation by MALDI-TOF mass spectroscopy. Scanning electron micrographs of the patient's fibrin clot were found to be abnormal.

CONCLUSIONS

The case of dysfibrinogenemia Aalpha R16C-fibrinogen Nový Jicín and the case of dysfibrinogenemia Aalpha R16H were found by routine coagulation testing and were genetically identified.

Fibrinogen Saint-Germain I: a case of the heterozygous Aalpha GLY 12 --> VAL fibrinogen variant

A fibrinogen variant was suspected based on the results of routine coagulation tests in a 2-year-old asymptomatic child. Coagulation studies showed marked prolongation of both the thrombin and reptilase times, and discrepancy was noted between the level of plasma fibrinogen as measured by a kinetic versus immunological determination. Family studies revealed that the father beared the same abnormality. Studies of purified fibrinogen revealed an impaired release of both fibrinopeptides by thrombin. Fibrin monomer polymerization and fibrin stabilization were normal. DNA sequencing revealed a heterozygous G --> T point mutation in exon 2 of the gene coding for the Aalpha chain, which substituted a Gly for Val at position 12. Although the mutation is the same as in fibrinogen Rouen, fibrinogen Saint-Germain I shows a different fibrinopeptide release pattern and a mild factor V deficiency.