The mitochondrial enzyme ETHE1 is a persulfide dioxygenase essential for cellular sulfide detoxification, and its deficiency causes the severe and complex inherited metabolic disorder ethylmalonic encephalopathy (EE). In spite of well-described clinical symptoms of the disease, detailed cellular and molecular characterization is still ambiguous. TMT-based large-scale proteomics was performed to broadly elucidate cellular consequences of the ETHE1 deficiency in the patient fibroblasts.