Mucopolysaccharidosis type III may manifest as cognitive decline, leading to an imprecise diagnosis of ADHD or early‐onset dementia (Xiao et al. 2022; Pará et al. 2021) Adult‐onset Ornithine Transcarbamylase Deficiency may present with hyperammonemic encephalopathy, which may incorrectly incline a clinician toward a diagnosis of hepatic encephalopathy associated with alcohol use disorder (Niclasen et al. 2022). The gene discussed is OTC; the disease is Mental deterioration.