The present study aimed to evaluate genetic variants in <i>ABCC8</i>, <i>KCNJ11,</i> and <i>HADH</i> genes as causative genes for CHI in the Iranian population.<h4>Methods</h4>The present case series took place in Mashhad, Iran, within 11 years. The gene discussed is HADH; the disease is congenital isolated hyperinsulinism.