Aims/hypothesis Individuals with heterozygous activating mutations of the KCNJ11 gene encoding a subunit of the ATP-sensitive potassium channel (KATP) can usually be treated with oral sulfonylurea (SU) pills in lieu of insulin injections. The aim of this study was to test our hypothesis that younger age at the time of initiation of SU therapy is correlated with lower required doses of SU therapy, shorter transition time and decreased likelihood of requiring additional diabetes medications. Methods We performed a retrospective cohort study using data on 58 individuals with neonatal diabetes due to KCNJ11mutations identified through the University of Chicago Monogenic Diabetes Registry (http://monogenicdiabetes.uchicago.edu/registry). We assessed the influence of age at initiation of SU therapy on treatment outcomes. Results HbA1c fell from an average of 8.5% (69 mmol/mol) before transition to 6.2% (44 mmol/mol) after SU therapy (p < 0.001). Age of initiation of SU correlated with the dose (mg kg−1 day−1) of SU required at follow-up (r = 0.80, p < 0.001). Similar associations were observed across mutation subtypes. Ten participants required additional glucose-lowering medications and all had initiated SU at age 13 years or older. No serious adverse events were reported. Conclusions/interpretation Earlier age at initiation of SU treatment is associated with improved response to SU therapy. Declining sensitivity to SU may be due to loss of beta cell mass over time in those treated with insulin. Our data support the need for early genetic diagnosis and appropriate personalised treatment in all cases of neonatal diabetes.

Aims GCK-MODY leads to mildly elevated blood glucose typically not requiring therapy. It has been described in all ethnicities, but mainly in Caucasian Europeans. Here we describe our United States cohort of GCK-MODY. Methods We examined the rates of detection of heterozygous mutations in the GCK gene in individuals referred to the US Monogenic Diabetes Registry with a phenotype consistent with GCK-MODY. We also assessed referral patterns, treatment, and demography, including ethnicity, of the cohort. Results Deleterious heterozygous GCK mutations were found in 54.7% of Registry probands selected for GCK sequencing for this study. Forty-nine percent were previously unnecessarily treated with glucose-lowering agents, causing hypoglycemia and other adverse effects in some of the subjects. The proportion of probands found to have a GCK mutation through research based testing was similar across each ethnic group. However, together African American, Latino and Asian subjects represented only 20.5% of screened probands and 17.2% of those with GCK-MODY, despite higher overall diabetes prevalence in these groups. Conclusions Our data show a high detection rate of GCK-MODY is possible based on clinical phenotype, and that prior to genetic diagnosis, a large percentage are inappropriately treated with glucose-lowering therapies. We also find low minority representation in our Registry, which may be due to disparities in diagnostic diabetes genetic testing, and is an area needing further investigation.