GSTZ1 and hyperinsulinemic hypoglycemia, familial, 4: Screening for tyrosinemia type I (FAH, MIM *613871, #276700) using DBS succinylacetone as a biomarker had a PPV of 9% from 2018 to 2022 [4,8], this biomarker often reveals variants in GSTZ1 (MIM *603758, #617596), which causes the non-clinical entity maleylacetoacetate isomerase deficiency [9].