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.

Methylenetetrahydrofolate reductase polymorphisms as genetic markers to predict homocysteinemia and clinical severity in sickle cell disease

Aim: The present study observed the relationship between the methylenetetrahydrofolate reductase genotypes and clinical outcome in children with sickle cell disorder. Methodology: A total of 249 children were recruited for the study and evaluated clinically for calculating severity score, homocysteine levels and C677T and A1298C genotyping. Results: The frequencies of variant genotypes were 28.1% CT/TT677 and 69.1% AC/CC1298. Plasma homocysteine was significantly elevated in variant groups (p < 0.001). Both the genotypes accorded significant association with homocysteinemia (p < 0.001). Vascular crisis (p = 0.04), frequency of hospitalization (p < 0.001) and severity score (p = 0.02) revealed association with C677T and not with A1298C. The CT/TT677 genotypes showed 3.39-times (p = 0.032) increase in a higher score for severity. Conclusion: C677T depicted significant association with clinical severity in study population.