Should we screen Eastern Mediterranean sickle beta-thalassemia patients for inherited thrombophilia?

Factor V Leiden G1691A, Prothrombin G20210A, and MTHFR C677T and A1298C Mutations in Patients With Sickle Cell Disease in Tunisia

Sickle cell disease is a genetic disorder characterized by a hypercoagulable state. Several complications in this hemoglobinopathy are increased by thrombosis. Factor V Leiden (FVL), prothrombin (PRT) G20210A, and methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C mutations are major inherited risk factors of thrombotic complications. In this study, our aim was to compare the frequencies of these mutations in sickle cell patients with healthy controls. The study population comprised 35 homozygous Hb S (HBB: c.20A>T) patients, 29 compound heterozygous patients [16 Hb S/β⁰-thalassemia (β⁰-thal), four Hb S/β⁺-thal, seven Hb S/Hb C (HBB: c.19G>A) and two Hb S/Hb O-Arab (HBB: c.364G>A)] and 100 healthy subjects. All patients and controls were subjected to laboratory investigations as well as mutation genotyping. Our findings showed a severe anemia with the lowest values of protein S (PS), protein C (PC) and antithrombin (AT) in the homozygous Hb S group compared to Hb S/Hb C and Hb S/β-thal subjects. No significant difference in FVL genotype between patients and controls was observed, whereas high frequencies of PRT G20210A, MTHFR C677T and MTHFR A1298C mutations in the Hb S patients and a significant association between the MTHFR C677T mutation and Hb S/β⁰-thal were found.

Role of the hemostatic system on sickle cell disease pathophysiology and potential therapeutics

Recent studies suggest that sickle cell disease (SCD) is a hypercoagulable state contributing to vaso-occlusive events in the microcirculation, resulting in acute and chronic sickle cell-related organ damage. In this article, we review the existing evidence for contribution of hemostatic system perturbation to SCD pathophysiology. We also review the data showing increased risk of thromboembolic events, particularly newer information on the incidence of venous thromboembolism. Finally, the potential role of platelet inhibitors and anticoagulants in SCD is briefly reviewed.

Sickle cell disease and venous thromboembolism

Hemoglobin S in homozygous state or in combination with one of the structural variants of Hb D-Punjab, Hb O-Arab, Hb C or β-thalassemia mutation results in sickle cell disease (SCD) that is characterized by chronic hemolytic anemia and tissue injury secondary to vasooclusion. A chronic hypercoagulable state in SCD has been established with the increased risk of thromboembolic complications in these patients. The goal of present review is to survey of the literature related to thromboembolic events and genetic risk factors involved in the manifestation of these events in SCD patients with focus on studies from Mediterranean countries. Also, this review covers the pathogenesis of hypercoagulability and alteration in the components of hemostasis system.

Thrombophilic mutations among Southern Iranian patients with sickle cell disease: high prevalence of factor V Leiden

BACKGROUND

A hypercoagulable state in sickle cell disease (SCD) and beta thalassemia has been established and thrombosis is an important aspect of the clinical spectrum of sickle cell disease. In a case-control study, the prevalence of factor V Leiden and prothrombin G20210A mutations were investigated among SCD patients from Southern Iran.

METHODS

Patients comprised 60 individuals with SCD; of them 35 were with sickle cell anemia (SS) including 21 males and 14 females aged 17.2+/-8.3 years, 15 were sickle cell trait (AS) consisted of nine males and six females aged 30+/-15.4 years and 10 were sickle/beta thalassemia (S/Thal) (three males and seven females) aged 24.6+/-10.4 years. The control group were 126 apparently healthy individuals (50 males and 76 females) aged 20.1+/-9.8 years. Genotyping was done by polymerase chain reaction restriction fragment-length polymorphism (PCR-RFLP) using Mnl I and Hind III for factor V Leiden and prothrombin G20210A, respectively.

RESULTS

Heterozygous factor V Leiden mutation was found in five of 35 (14.3%) SS patients, two of 15 (13.3%) AS individuals, one (a sickle/beta-zero thalassemia patient with IVSII.1 G-->A mutation) of 10 S/Thal patients (10%), and two of 126 (1.6%) control subjects (P<0.05). However, only one AS individual (6.7%) was found to be a carrier for prothrombin G20210A compared to five of 126 (4%) healthy individuals. Adjusted logistic regression analysis for the effects of age and sex was performed and a significant association was found between factor V Leiden mutation and sickle cell anemia with odds ratios (OR) of 6.5 (95% confidence intervals [CI] 1.19-35.33, P=0.03) in SS patients. However, increased prevalence of the factor V Leiden in AS individuals and S/Thal patients was not statistically significant compared to controls (OR 3.84, 95% CI 0.49-29.9, P=0.19 and OR 3.77, 95% CI 0.31-45.9, P=0.29, respectively).

CONCLUSIONS

Our findings indicate a significant correlation between factor V Leiden and sickle cell anemia among Iranian patients. Association between venous thrombophilia and factor V Leiden mutation in Iranians with sickle cell anemia should be further studied.

Screening for inherited thrombophilia might be warranted among Eastern Mediterranean sickle-beta-0 thalassemia patients

BACKGROUND

The role of genetic thrombophilia in the development of both micro and macro vascular complications in patients with hemoglobinopathies (Sickle cell disease and thalassemia) have been investigated with some studies negating its role while others suggesting it. Lebanon is known to harbor sickle cell disease, thalassemia and sickle beta-thalassemia hemoglobinopathy patients along with a documented high prevalence of genetic thrombophilia mutations.

METHODS

Twelve sickle beta-0-thalassemia patients with no pervious history of thrombotic events were selected. These patients underwent a physical examination with history, echo Doppler, along with blood withdrawal for complete blood count and PCR analysis of a sample of DNA for Factor V Leiden G1691A, Factor II G20210A, and MTHFR C677T. Results were compared to a historical control of 50 Lebanese controls and 50 LebaneseThalassemia Intermedia (TI) patients.

RESULTS

The results showed that 42%, 59%, and 8% of patients carried heterozygous Factor V Leiden, abnormal (homozygous & heterozygous) MTHFR, and heterozygous Factor II mutations respectively. The sickle-thalassemia patients were 5.24 and 4.39 times more likely to have Factor V Leiden as compared to the normal controls and TI patients respectively (p < 0.05).

DISCUSSION

The increased prevalence of more than one prothrombotic genetic mutation among the group indicates a probable clustering phenomenon, unknown to us to which the high consanguinity rate (77%) may have contributed. The role of the specific MTHFR and Factor V Leiden double heterozygous combination in incidence, recurrence, and guidance of duration of therapy in VTE is not well defined in the literature despite the recognized higher risk of thrombosis among this patient population. Our findings suggest that genetic thrombophilia workup is necessary in patients with sickle-beta zero thalassemia presenting with thrombotic events and studies that include a larger number of patients are necessary in order to define specific guidelines.