INS and diabetes mellitus: It has been shown that mutations in the KCNJ11 gene are the most common cause of PNDM.3 R201H is a mutation in the KCNJ11 gene that usually presents in isolated diabetes, with no neurological phenotype.5 Pearson et al showed the successful switch from insulin to oral sulfonyurea in 90% of patients with KCNJ11 mutations.4