Hence, data from four studies including 84 SCD patients with ischemic stroke and 186 without ischemic stroke revealed a similar pooled prevalence of MTHFR TT between the two groups (5.9% vs. 3.7%, p = 0.47) with medium heterogeneity (I2 = 32.6%, p = 0.21); however, removal of the study with the youngest participants [49] revealed a significant effect size (p = 0.006) with no heterogeneity (Figure 6). This evidence concerns the gene MTHFR and Schnyder corneal dystrophy.