Newborn screening (NBS) for hepatorenal tyrosinemia type I (HT1) based on a determination of succinylacetone is performed in countries worldwide. Recently, biallelic pathogenic variants in GSTZ1 underlying maleylacetoacetate isomerase (MAAI) deficiency have been described as a differential diagnosis in individuals with slightly elevated succinylacetone detected by NBS. We report the experience with NBS for HT1 over 53 months in a large German NBS center and the identification …