Of the 25 cases characterized by sanger sequencing, we identified 7 patients with mutations in IL2RG, 1 patient with IL7Ra deficiency, 5 with ADA deficiency, 1 with PNP defect, 1 with AK2 defect,9 patients with RAG1/2 deficiency and 1 case of ZAP70 defect. The gene discussed is IL2RG; the disease is hyperinsulinemic hypoglycemia, familial, 4.