Puça et al., 2024 [48], investigated the influence of monoamine oxidase-A (MAO-A) on PQ metabolism and its impact on vivax malaria relapses; the authors observed that 30% (n = 100) impaired CYP2D6 activity, inferred from genotype data (AS ≤ 1.0), and 31% carried low-expression MAO-A variants; however, no differences in PQ levels were documented between high- and low-expression MAO-A variants [median = 179.0 ng/mL (IQR = 146.0, 232.0) and 188.0 ng/mL (119.0, 217.5), respectively, p = 0.907] in impaired CYP2D6 activity. The gene discussed is CYP2D6; the disease is Plasmodium vivax malaria.