Extraoral halitosis due to methanethiol oxidase deficiency (EHMTO) is a malodor syndrome resulting from an inborn error of metabolism. Breath odor is cabbage-like and results from high levels of methanethiol and dimethylsulfide in breath. Elevated urinary excretion of dimethylsulfone (DMSO2) is diagnostic (Pol et al., 2018). [from OMIM]