evidence: Keywords: MTHFR; genotype-phenotype correlation; homocystinuria; remethylation defects. [...] MTHFR: Addressing Genetic Counseling Dilemmas Using Evidence-Based Literature.J Genet Couns. 2016 Oct;25(5):901-11. doi: 10.1007/s10897-016-9956-7. Epub 2016 Apr 30. J Genet Couns. 2016. PMID: 27130656 Review. Determination and interpretation of MTHFR gene mutations in gynecology and internal medicine.Pol Arch Intern Med. 2019 Oct 30;129(10):728-732. doi: 10.20452/pamw.15039. Epub 2019 Oct 30. Pol Arch Intern Med. 2019. PMID: 31670725 Review. No abstract available.