MTHFR and Schnyder corneal dystrophy: However, this does not mean that MTHFR has no relevance in SCD: a recent article demonstrated that the co-inheritance of HbSS and MTHFR TT negatively affects the antioxidant capacity of SCD patients [65]: indeed, a low MTHFR activity reduces the production of 5-methyl tetrahydrofolate, leading to lower plasma and erythrocyte folate concentrations [66] and to a decreased antioxidant effect against superoxide anion [67].