Genetic variations of critical enzymes (e.g., Methyleneterahydrofolate reductase [MTHFR], methionine synthase [MS], methionine synthase reductase [MTRR], and cystathionine‐beta‐synthase [CBS]) in Hcy metabolism, deficiency of B‐vitamins (B2, B6, B9, and B12), unhealthy living habit (smoking and alcoholism), renal failure, and medications can lead to Hcy accumulation and increase of plasma Hcy levels.76 The gene discussed is MTR; the disease is alcohol dependence.