DEND Syndrome with Heterozygous KCNJ11 Mutation Successfully Treated with Sulfonylurea.

Permanent neonatal diabetes mellitus (PNDM) is caused by mutations in the ATP-sensitive potassium channel (KATP channel) subunits. Developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome is the most severe form of PNDM and is characterized by various neurologic features. We report on a patient with DEND syndrome following initial misdiagnosis with type 1 DM, who was successfully switched from insulin to sulfonylurea therapy. A 50-day-old male presented with fever and seizure, complicated by persistent hyperglycemia. Insulin therapy was initiated. At 10 months of age, the patient was unable to hold his head up and make eye contact with others. At 17.9 years of age, direct sequencing of KCNJ11 identified a heterozygous mutation of c.602G>A (p.R201H). Since then, treatment with gliclazide was initiated and the insulin dose was gradually reduced. Following 3 months, insulin was discontinued with a gliclazide dose of 2.4 mg/kg. The patient continued to have excellent glycemic control with a glycated hemoglobin (HbA1c) level of 5.8% after 5 months. However, the patient's psychomotor retardation did not improve. This study reports the first case of DEND syndrome in Korea caused by a KCNJ11 mutation and emphasizes the necessity to screen mutations in KATP channel genes in patients with neonatal diabetes.