For further diagnostic work-up, a virtual panel from exome sequencing focusing on the genes FAH (Tyrosinemia type I, MIM #276700) and GSTZ1 (Maleylaceoacetate Isomerase Deficiency, MIM #617596) was performed in leucocyte-derived DNA of the index. The gene discussed is GSTZ1; the disease is hyperinsulinemic hypoglycemia, familial, 4.