Updated prevalence of monogenic diabetes in Australia: Fremantle Diabetes Study Phase 2

To the Editor: Based on Fremantle Diabetes Study Phase 2 (FDS2) data, we reported in this Journal that the prevalence of maturity‐onset diabetes of the young (MODY) and permanent neonatal diabetes in an urban Australian population was 0.24% and 0.12%, respectively, of people diagnosed with diabetes.1 A further FDS2 participant among those identified as probably having MODY by clinical risk prediction was the only one with a novel heterozygous missense variant (Ala161Thr) in the KCNJ11 gene which encodes the pore‐forming KIR6.2 subunit of the pancreatic β‐cell adenosine triphosphate‐dependent potassium channel.2 This variant was not considered to be a cause of MODY at the time of our publication in 2017,1 but evidence has since emerged that it is a pathogenic activating mutation. It has been identified in two other patients with neonatal diabetes diagnosed before 9 months of age who were responsive to sulfonylurea therapy, and in another diagnosed at 14 years of age who was glutamic acid decarboxylase and islet antigen 2 antibody negative, and had a low (5th percentile) type 1 genetic risk score,3 a body mass index of 21, a stimulated serum C‐peptide concentration of 289 pmol/L (fasting range, 260–1030 pmol/L) 11 years after diagnosis, and a family history of non‐insulin‐requiring diabetes in her brother and mother (both diagnosed at 18 years of age) and maternal uncle and grandfather (unpublished data, Molecular Genetics Laboratory, Royal Devon and Exeter NHS Foundation Trust).