Factor V-Leiden, prothrombin G20210A, and MTHFR C677T mutations among patients with sickle cell disease in Eastern Saudi Arabia

Impact of Genetic Variations on Thromboembolic Risk in Saudis with Sickle Cell Disease

BACKGROUND

Sickle cell disease (SCD) is a Mendelian disease characterized by multigenic phenotypes. Previous reports indicated a higher rate of thromboembolic events (TEEs) in SCD patients. A number of candidate polymorphisms in certain genes (e.g., FVL, PRT, and MTHFR) were previously reported as risk factors for TEEs in different clinical conditions. This study aimed to genotype these genes and other loci predicted to underlie TEEs in SCD patients.

METHODOLOGY

A multi-center genome-wide association study (GWAS) involving Saudi SCD adult patients with a history of TEEs (n = 65) and control patients without TEE history (n = 285) was performed. Genotyping used the 10× Affymetrix Axiom array, which includes 683,030 markers. Fisher's exact test was used to generate p-values of TEE associations with each single-nucleotide polymorphism (SNP). The haplotype analysis software tool version 1.05, designed by the University of Göttingen, Germany, was used to identify the common inherited haplotypes.

RESULTS

No association was identified between the targeted single-nucleotide polymorphism rs1801133 in MTHFR and TEEs in SCD (p = 0.79). The allele frequency of rs6025 in FVL and rs1799963 in PRT in our cohort was extremely low (<0.01); thus, both variants were excluded from the analysis as no meaningful comparison was possible. In contrast, the GWAS analysis showed novel genome-wide associations (p < 5 × 10-8) with seven signals; five of them were located on Chr 11 (rs35390334, rs331532, rs317777, rs147062602, and rs372091), one SNP on Chr 20 (rs139341092), and another on Chr 9 (rs76076035). The other 34 SNPs located on known genes were also detected at a signal threshold of p < 5 × 10-6. Seven of the identified variants are located in olfactory receptor family 51 genes (OR51B5, OR51V1, OR51A1P, and OR51E2), and five variants were related to family 52 genes (OR52A5, OR52K1, OR52K2, and OR52T1P). The previously reported association between rs5006884-A in OR51B5 and fetal hemoglobin (HbF) levels was confirmed in our study, which showed significantly lower levels of HbF (p = 0.002) and less allele frequency (p = 0.003) in the TEE cases than in the controls. The assessment of the haplotype inheritance pattern involved the top ten significant markers with no LD (rs353988334, rs317777, rs14788626882, rs49188823, rs139349992, rs76076035, rs73395847, rs1368823, rs8888834548, and rs1455957). A haplotype analysis revealed significant associations between two haplotypes (a risk, TT-AA-del-AA-ins-CT-TT-CC-CC-AA, and a reverse protective, CC-GG-ins-GG-del-TT-CC-TT-GG-GG) and TEEs in SCD (p = 0.024, OR = 6.16, CI = 1.34-28.24, and p = 0.019, OR = 0.33, CI = 0.13-0.85, respectively).

CONCLUSIONS

Seven markers showed novel genome-wide associations; two of them were exonic variants (rs317777 in OLFM5P and rs147062602 in OR51B5), and less significant associations (p < 5 × 10-6) were identified for 34 other variants in known genes with TEEs in SCD. Moreover, two 10-SNP common haplotypes were determined with contradictory effects. Further replication of these findings is needed.

Relevance of Plasma Homocysteine and Methylenetetrahydrofolate Reductase 677TT Genotype in Sickle Cell Disease: A Systematic Review and Meta-Analysis

We evaluated the relevance of plasma homocysteine (HC) and the TT genotype of the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism (rs1801133) in sickle cell disease (SCD) and associated vaso-occlusive crisis (VOC) and ischemic stroke (IS). We identified in Embase and Medline 22 studies on plasma HC and 22 on MTHFR genotypes. Due to age-related HC differences, adult and paediatric SCD were separated: 879 adult SCD and 834 controls (CTR) yielded a neutral effect size; 427 paediatric SCD and 625 CTR favoured SCD (p = 0.001) with wide heterogeneity (I2 = 95.5%) and were sub-grouped by country: six studies (Dutch Antilles n = 1, USA n = 5) yielded a neutral effect size, four (India n = 1, Arab countries n = 3) favoured SCD (p < 0.0001). Moreover, 249 SCD in VOC and 419 out of VOC yielded a neutral effect size. The pooled prevalence of the MTHFR TT genotype in 267 SCD equalled that of 1199 CTR (4.26% vs. 2.86%, p = 0.45), and in 84 SCD with IS equalled that of 86 without IS (5.9% vs. 3.7%, p = 0.47); removal of one paediatric study yielded a significant effect size (p = 0.006). Plasma HC in paediatric SCD from Middle East and India was higher, possibly due to vitamin deficiencies. Despite its low prevalence in SCD, the MTHFR TT genotype relates to adult IS.

Prevalence of methylenetetrahydrofolate reductase gene polymorphisms (C677T, and A1298C) among Saudi children receiving dental treatment

BACKGROUND

Methylenetetrahydrofolate reductase, the encoded by the MTHFR gene, plays a crucial role in converting the amino acid homocysteine to methionine. Two polymorphisms of the MTHFR gene, C677T and A1298C, reportedly reduce enzyme activity, resulting in hyperhomocysteinemia. Patients with C677T and A1298C polymorphisms may be at higher risk for developing abnormal hyperhomocysteinemia, which has been linked to catastrophic neurological including fatal outcomes.

OBJECTIVE

Determine the prevalence of the MTHFR gene variants C677T and A1298C among pediatric dental patients treated at King Abdulaziz University Hospital.

DESIGN

Cross-sectional.

SETTING

Clinics of pediatric dentistry department.

SUBJECTS AND METHODS

Healthy Saudi children 6-12 years old with no known allergies were screened for eligibility between May and December 2019. A single investigator collected saliva samples. The MTHFR C677T and A1298C polymorphisms were analyzed using polymerase chain reaction and restriction fragment length polymorphism.

MAIN OUTCOME MEASURE

The prevalence of MTHFR gene variants (C677T and A1298C) among the subjects.

SAMPLE SIZE

138.

RESULTS

MTHFR C677T polymorphism was present in 36.2% of the sample and 90.0% of children carrying this allele were heterozygotes. MTHFR A1298C polymorphism was present in 91.3% of the sample and 77.0% of the children carrying this allele were heterozygotes. No linkage disequilibrium between MTHFR C677T and MTHFR A1298C was observed within this sample.

CONCLUSIONS

Our study found a high frequency of the MTHFR A1298C genotype, which was substantially more abundant than expected based on a Hardy-Weinberg distribution. Therefore, caution is advised in using N2O in Saudi children as the increased prevalence of this MTHFR allele may increase the incidence of serious adverse effects among these children.

LIMITATIONS

Further studies are recommended with a larger sample size from randomly selected hospitals from different regions of Saudi Arabia.

CONFLICT OF INTEREST

None.

Pulmonary and Paradoxical Embolism after Slow Pathway Ablation: A Thrombotic Disorder Unmasked by a Rare Complication

Cardiac electrophysiology study (EPS) and catheter ablation procedure are established diagnostic and therapeutic procedures for cardiac arrhythmias. Pulmonary embolism (PE) is a relatively rare but potentially fatal complication of Cardiac electrophysiology study (EPS). The paradoxical embolism (PDE) occurs due to an intracardiac defect with a right to left shunt with patent foramen ovale (PFO) being the most common cause. The simultaneous occurrence of PE and PDE is rare. Here we present a case of PE and PDE after EPS and radiofrequency catheter ablation (RFCA) of the slow pathway in a patient with recurrent supraventricular tachycardia (SVT) due to atrioventricular nodal reentry tachycardia (AVNRT). To our knowledge, such a case of PE and PDE has not been reported after SVT ablation.

Association between MTHFR 677C>T polymorphism and vascular complications in sickle cell disease: A meta-analysis

Sickle cell disease (SCD) is considered as a vascular disease due to its chronic vascular manifestations such as leg ulcers, priapism, acute chest syndrome (ACS), stroke, retinopathy, renal insufficiency, pulmonary hypertension, avascular necrosis of the femoral head (AVNF) and splenic infarction. Emerging evidence has shown that the MTHFR 677C>T variant allele is associated with vascular complications (VC) in patients with SCD; however, results from individual studies are inconclusive. The aim of this meta-analysis is to evaluate the association between the MTHFR 677C>T polymorphism and the susceptibility for VC in SCD patients. Articles published in English were collected from Medline, PubMed, Embase, and Web of Science databases. As a result, 11 studies in different populations including 614 SCD patients with VC, and 559 patients without VC were selected. Meta-analysis in fixed effect model showed that mutant genotypes (CT+TT vs. CC) of the MTHFR 677C>T polymorphism is associated with increased risk of vascular complication (OR=1.81, 95% CI=1.37-2.40, P<0.001). This study did not demonstrate publication bias or between-study heterogeneity. Our meta-analysis establishes that the MTHFR 677C>T polymorphism as a high-penetrant risk factor for VC in SCD patients. Further research is needed to support the clinical utility of MTHFR genetic testing for predicting VC in patients with sickle cell disease.

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.

Factor V Leiden G1691A and prothrombin G20210A mutations among Palestinian patients with sickle cell disease

Background

Vascular thrombosis is an important pathophysiological aspect of sickle cell disease (SCD). This study aimed to investigate the prevalence and clinical impact of factor V Leiden G1691A (FVL) and prothrombin G20210A mutations among Palestinian sickle cell disease (SCD) patients.

Methods

A total of 117 SCD patients, including 59 patients with sickle cell anemia (SS), 33 patients with sickle β-thalassemia and 25 individuals with sickle cell trait (AS) were studied. The control group consisted of 118 healthy individuals. FVL and prothrombin G20210A mutations were determined by RFLP PCR.

Results

Analysis of the clinical history of SCD patients revealed that seven patients have had vascular complications such as ischemic stroke or deep vein thrombosis. In SCD patients, the inheritance of the FVL mutation showed a significantly higher incidence of pain in joints, chest and abdomen as well as regular dependence on blood transfusion compared to SCD with the wild type. Age- and sex-adjusted logistic regression analysis revealed a significant association between FVL and sickle cell anemia with an odds ratio (OR) of 5.6 (95% confidence intervals [CI] of 1.91–39.4, P = 0.039) in SS patients. However, increased prevalence of the FVL in AS subjects and sickle β-thalassemia patients was not statistically significant compared to controls (OR 3.97, 95% CI 0.51–28.6, P = 0.17 and OR 3.59, 95% CI 0.35–41.6, P = 0.26, respectively). The distribution of prothrombin G20210A mutation among SCD patients compared to controls was not significantly different, thus our findings do not support an association of this mutation with SCD.

Conclusions

FVL was more prevalent among SS patients compared to controls and it was associated with higher incidence of disease complications among SCD patients.

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.

The Prevalence of Factor V Leiden (G1691A) and Methylenetetrahydrofolate Reductase C677T Mutations in Sickle Cell Disease in Western India

The prevalence of the Factor V Leiden (FVL; G1691A) mutation and the methylenetetrahydrofolate reductase (MTHFR; C677T) mutation was determined in 180 patients with sickle cell (SS) disease (126 sickle homozygous and 54 sickle β-thalassaemia—age 1-47 years) and in 130 healthy controls. The FVL mutation in the heterozygous state was present in only 3 patients with SS disease and was absent in the controls. Genotyping of MTHFR 677C > T revealed increased frequency of the C allele than the T allele in patients as well as in controls. This suggests that these genetic markers may not be major risk factors for a hypercoagulable state in Indian patients with SS disease.

Prevalence of Factor V Leiden G1691A, MTHFR C677T, and Prothrombin G20210A Among Asian Indian Sickle Cell Patients

The prevalence of factor V (FV) Leiden G1691A, prothrombin G20210A, and methylenetetrahydrofolate reductase (MTHFR) C677T mutations were investigated among 90 sickle trait, 61 sickle homozygous, 75 sickle beta thalassemia, and 15 HbSD Asian Indian sickle cell patients. In all, 297 healthy controls were evaluated to compare the polymorphism frequency. The prevalence of FV Leiden heterozygous G>A were significant in the group ( P = .02), while PRT G20210A polymorphism was not seen among patients as well as controls. However, an increased frequency of the MTHFR 677 C>T genotype was seen among patients as well as controls, but this was not statistically significant ( P = .13). This suggested a low impact of inherited hypercoagulability risk factors in the pathogenesis of sickle cell disease and/or its complications.

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.

Association of the Methylenetetrahydrofolate Reductase A1298C but not the C677T Single Nucleotide Polymorphism with Sickle Cell Disease in Bahrain

The association of methylenetetrahydrofolate reductase (MTHFR) gene mutations, C677T and A1298C, together with changes in homocysteine (Hcy) levels was investigated in 106 sickle cell disease patients and 156 healthy controls from Bahrain. The mutation analysis was done by restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR). While the frequencies of the mutant alleles C677T and A1298C were comparable between patients and controls, the frequency of the A1298C (C/C) (p = 0.03) but not C677T (T/T) (p = 0.67) genotype, and of the 677T/1298C haplotype were significantly higher in the patients (p = 0.05). Homocysteine levels were normal in all subjects. This suggests that the A1298C, but not C677T, mutation is associated with the genotype of sickle cell disease.

HLA class II haplotypes distinctly associated with vaso-occlusion in children with sickle cell disease

We investigated the association of HLA class II alleles and haplotypes with sickle cell anemia vaso-occlusive crisis (VOC). DRB1*100101 was positively associated, while DRB1*140101, DRB1*150101, and DQB1*060101 were negatively associated, with VOC. Both susceptible (DRB1*100101-DQB1*050101) and protective (DRB1*110101-DQB1*030101 and DRB1*150101-DQB1*060101) haplotypes were identified, indicating that HLA class II haplotypes influence VOC risk.

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.