Islet-specific antibody seroconversion in patients with long duration of permanent neonatal diabetes caused by mutations in the KCNJ11 gene.

H eterozygous activating mutations in the KCNJ11 gene are a common cause of permanent neonatal diabetes (PNDM) (1,2). In contrast to the autoimmune type 1 diabetes, patients with KCNJ11 mutations do not have serological markers of autoimmune -cell destruction at disease onset (1,3–5). In such patients, hyperglycemia does not result from insulin-secreting cell destruction but rather from impaired insulin secretion. In addition, the majority of cases can be corrected with sulfonylurea therapy (2,6). Here, we report that carriers of the KCNJ11 mutation that are immunonegative at onset may show presence of islet antibodies in the further course of the disease.