Hypodysfibrinogenemia: A novel abnormal fibrinogen associated with bleeding and thrombotic complications.

BACKGROUND: Congenital disorders of fibrinogen are rare diseases resulting in the complete absence (afibrinogenemia), reduced concentration (hypofibrinogenemia) or altered function of circulating fibrinogen (dysfibrinogenemia). A combination of two different fibrinogen abnormalities with a significant functional and secretion defect (hypodysfibrinogenemia) reported in Tunisian family members, was investigated in this study. METHODS: The coagulation-related tests, kinetics of fibrin polymerization and lysis and fibrinogen analysis using gel electrophoresis were performed in the family members to characterize fibrinogen abnormalities. All exons including exon-intron boundaries of fibrinogen genes were screened by direct sequencing. RESULTS: Mutational screening of the fibrinogen genes disclosed novel missense mutations, BßCys197Arg, in exon 4 of the fibrinogen Bß-chain gene. After the loose of its partner in Bß-chain, the γCys135 was probably disulfide-bridged to its corresponding Cys residue of another abnormal fibrinogen molecule, forming dimmer with an abnormal electrophoretic profile. Homozygous form carried by the proband found to be directly involved in the bleeding phenotype by affecting fibrin polymerization. In contrast, affected family members bearing the heterozygous mutation showed an impaired fibrin polymerization and fibrinolysis leading to thrombosis. CONCLUSION: These results suggest that this mutation could alter the extremely conserved conformations of fibrinogen D domain and D-D lateral regions on fibrin assembly.

Congenital afibrinogenemia: Identification and characterization of two novel homozygous fibrinogen Aα and Bß chain mutations in two Tunisian families.

INTRODUCTION: Inherited abnormalities of fibrinogen (FG) are rare coagulation disorders divided into two types: quantitative abnormalities (afibrinogenemia and hypofibrinogenemia) or qualitative abnormalities (dysfibrinogenemia and hypo-dysfibrinogenemia) of circulating fibrinogen. In particular, congenital afibrinogenemia is inherited as an autosomal recessive mode and is usually determined by homozygous or compound heterozygous mutations affecting any of the three fibrinogen genes (FGA, FGB and FGG), resulting in the complete absence or extremely reduced amount of fibrinogen. The aim of the present study was to characterize the fibrinogen abnormalities in two Tunisian families. METHODS: Coagulation studies were performed on the patients and family members. All the exons and the flanking intron regions of fibrinogen genes were screened by direct sequencing. RESULTS: Probands had concomitant bleeding complications with infinitely prolonged standard coagulation assays. Mutational screening of the fibrinogen gene cluster of each proband, disclosed two previously undescribed homozygous point mutations. The first mutation was a major truncation (AαArg252Stop) leads to a severe premature termination codon in the exon 5 of the FGA gene. This mutation defines in vivo the importance of the αC flexible segment in the secretion of a stable fibrinogen molecule. The second afibrinogenemic mutation (BßGly295Ala) occurs in the exon 7 of the FGB gene. This missense mutation would probably lead to significant conformational change not allowing the expression of the fibrinogen protein. CONCLUSION: Current molecular characterization of these two fibrinogen abnormalities confirms the importance of the first portion of αC-region (αC-connector) as well as the Bß globular domain in the secretion processes.

Molecular identification of Gd A- and Gd B- G6PD deficient variants by ARMS-PCR in a Tunisian population.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzymopathy. More than 200 mutations in the G6PD gene have been described. In Tunisia, the A-African and the B-Mediterranean mutations predominate the mutational spectrum. The purpose of this study was to apply the amplification refractory mutation system (ARMS-PCR) to the identification of Gd A+, Gd A- and Gd B- variants in a cohort of deficient individuals and to establish a phenotype/genotype association. 90 subjects were screened for enzymatic deficiency by spectrophotometric assay. The molecular analyses were performed in a group of 50 unrelated patients. Of the 54 altered chromosomes examined, 60% had the Gd A- mutation, 18% showed the Gd B- mutation and in 20% of cases, no mutations have been identified. The ARMS-PCR showed complete concordance with the endonuclease cleavage reference method and agreed perfectly with previous Tunisian studies where Gd A- and Gd B- were the most encountered. Also, similarities in spectrum mutations with North African and Mediterranean countries suggest gene migration from Africa to Europe through Spain. In conclusion, ARMS has been introduced in this study for common G6PD alleles identification in Tunisia. It gives some advantages compared to the traditional endonuclease digestion method since it is more convenient and timesaving and also offers the possibility to be applied in mass screening surveys.

Red cell indices: differentiation between ß-thalassemia trait and iron deficiency anemia and application to sickle-cell disease and sickle-cell thalassemia.

BACKGROUND: In Tunisia, thalassemia and sickle cell disease represent the most prevalent monogenic hemoglobin disorders with 2.21% and 1.89% of carriers, respectively. This study aims to evaluate the diagnosis reliability of a series of red blood cell indices and parameters in differentiation of beta-thalassemia trait (ß-TT) from iron deficiency anemia (IDA) and between homozygous sickle cell disease (SS) and sickle cell-thalassemia (ST). METHODS: The study covered 384 patients divided into three groups. The first one is composed of 145 control group, the second consists of 57 ß-TT and 52 IDA subjects and the last one with 88 SS and 42 ST patients. We calculated sensitivity, specificity, positive-predictive values, negative-predictive values, percentage of correctly identified patients and Youden's index for each indice. We also established new cut-off values by receiver operating characteristic curves for each indice. An evaluation study was performed on another population composed of 106 ß-TT, 125 IDA, 31 SS and 17 ST patients. RESULTS: Srivastava Index, mean corpuscular hemoglobin, red blood cell, Mentzer Index (MI) and mean corpuscular hemoglobin concentration show the highest reliability in discriminating ß-TT from IDA with new cut-offs slightly different from those described in literature. Ehsani Index, mean corpuscular volume, MI, Shine and Lal Index and Sirdah Index are the most powerful in the differentiation between SS and ST. CONCLUSIONS: The effectiveness and the simplicity of calculation of these indices make them acceptable and easy to use for differential diagnosis.

Screening for deep venous thrombosis after idiopathic scoliosis surgery in children: a pilot study.

BACKGROUND: Venous thrombosis remains an uncommon disorder in childhood. However, the incidence appears to be increasing for a multitude of reasons. The aim of the study was to detect asymptomatic deep venous thrombosis and prothrombotic diseases in nonsyndromic children undergoing scoliosis surgery. METHODS: A prospective study including forty successive teenagers scheduled for posterior spinal fusion. Patients with scoliosis with a history of hemoglobinopathies, cardiac defects, blood clots, early onset osteoporosis, as well as patients with skeletal dysplasias and nonskeletal dysplastic syndromic entities have been excluded. The protocol was designed for active screening of deep venous thrombosis using color Doppler ultrasonography on a day before surgery and repeated on the 3rd, 7th and 15th day postoperatively. Evaluation of prothrombotic disorders included antithrombin and protein C activities, and total protein S antigen level. RESULTS: No patient has manifested clinical symptoms of venous thrombosis in our study. Preoperative Doppler and ultrasound examinations were normal in all patients. Although repeated Doppler ultrasonography demonstrated a transient small clot in two patients. Congenital antithrombin deficiency of 5% has been observed in one child only, without the development of deep venous thrombosis. CONCLUSION: Thromboembolic event seems to be rare after scoliosis surgery. Prophylaxis for venous thrombosis should not be recommended in such patient. But, larger series are required to confirm such results.

[Acquired isolated factor VII deficiency and bronchogenic carcinoma. A case report]. / Deficit acquis, isole en facteur VII et cancer bronchique. A propos d'un cas.

An acquired factor VII deficiency was identified in a 63-year-old man with bronchogenic carcinoma. Initial studies indicated a normal activated partial thromboplastin time and a prolonged prothrombin time. The factor VII level was 6%. No evidence of a factor VII inhibitor or inactivator was demonstrable. However, on account of the initial normal laboratory test of emostases, the partial correction of the prothrombin time with 50% normal plasma in vitro and the family history, the congenital deficiency in factor VII was ruled out. Whatever the mechanism involved, this factor VII deficiency was related to malignancy.