ChEBI: Itaconic acid is a dicarboxylic acid that is methacrylic acid in which one of the methyl hydrogens is substituted by a carboxylic acid group. It has a role as a fungal metabolite and a human metabolite. It is a dicarboxylic acid, an olefinic compound and a dicarboxylic fatty acid. It is functionally related to a succinic acid. It is a conjugate acid of an itaconate(2-).