Abstract Chronic increase and high level of glucose results in a metabolic disorder termed as Diabetes Mellitus. Diabetes occurs as a result of some genetic factors, namely the mutations of single gene. Permanent neonatal diabetes is very rare form of disorder, termed as monogenic diabetes. This type of rare diabetes presentation is seen in the child of age less than 6 months. Presenting the single case of neonatal diabetes reported from Chennai. A 2 month old female child is actually diagnosed with permanent neonatal diabetes-4 because of the heterozygous mutation of INS gene present in chromosome 11p15. Though the occurrence of permanent neonatal diabetes is very rare, this diagnosis has to be made when the infants are presenting with features of persistent hyperglycaemia and also in need of the insulin therapy. Children with the INS mutation will exhibit overall good prognosis when they are adequately managed with insulin therapy.