To assess whether the molecular abnormalities in the H2S oxidation pathway observed in patient fibroblasts were caused by CoQ10 deficiency independently from the primary molecular defects, we used two approaches: (i) We pharmacologically inhibited CoQ10 biosynthesis in wild‐type skin fibroblasts with 4‐nitrobenzoate (4‐NB), an analogue of 4‐hydroxybenzoate (4HB) that specifically inhibits the activity of COQ2 and causes CoQ10 deficiency (Forsman et al, 2010; Quinzii et al, 2012), and (ii) we knocked down ADCK3 in HeLa cells. The gene discussed is COQ8A; the disease is coenzyme Q10 deficiency.