Hcy-thiolactone and N-Hcy-proteins accumulate in intellectually disabled cystathionine β-synthase- and methylenetetrahydrofolate reductase-deficient patients [6] and are mechanistically linked to neurological diseases such as Alzheimer’s disease (AD) [9, 10], stroke [11], cognitive impairment [12], Parkinson’s disease [13], and neural tube defects [14, 15], as well as cardiovascular disease [16], cancer [17–19], and rheumatoid arthritis [20]. This evidence concerns the gene MTHFR and Alzheimer disease.