Results: In an NGS gene panel analysis for hereditary hemolytic anemias, we found a homozygotic change in the GCLC gene—G53.385.643c379C > T(homo)pArg127Cys—which confirms the diagnosis of gamma-glutamylcysteine synthetase deficiency. This evidence concerns the gene GCLC and hyperinsulinemic hypoglycemia, familial, 4.