Thus, the changes in the biosynthesis of amino acid neurotransmitters may contribute to the encephalopathy reported in patients and mice with fatal Coq9 mutations (Duncan et al, 2009; Garcia‐Corzo et al, 2013; Luna‐Sanchez et al, 2015; Danhauser et al, 2016) and add new evidences about the potential role of hydrogen sulfide as endogenous neuromodulator (Eto et al, 2002a,b). The gene discussed is COQ9; the disease is Encephalopathy.