Mutations in the KCNJ11 gene are responsible for the majority of permanent neonatal diabetes mellitus (PNDM) cases. Some mutations in this gene, including p.Q52R, are associated with the developmental delay, epilepsy, neonatal diabetes (DEND) syndrome. We describe a patient with PNDM who had no neurological finding although she was determined to have a novel mutation (p.Q52L) in the same residue of the KCNJ11 as in the previously reported cases with DEND syndrome. This case suggests that not all Q52 mutations in the KCNJ11 gene are necessarily related to DEND syndrome.