HNF1A gene mutations are the most common cause of maturity‐onset diabetes of the young (MODY) in the UK. Persons with HNF1A–MODY display sensitivity to sulphonylurea therapy; however, the long‐term efficacy is not established. There is limited literature as to the prevalence of micro‐ and macrovascular complications in this unique cohort. The aim of this study was to determine the natural progression and clinical management of HNF1A–MODY diabetes in a dedicated MODY clinic.

Sixty patients with HNF1A–MODY and a cohort of 60 BMI‐, age‐, ethnicity‐ and diabetes duration‐matched patients with Type 1 diabetes mellitus participated in the study. All patients were phenotyped in detail. Clinical follow‐up of the HNF1A–MODY cohort occurred on a bi‐annual basis.

Following a genetic diagnosis of MODY, the majority of the cohort treated with sulphonylurea therapy remained insulin independent at 84–month follow‐up (80%). The HbA_1c in the HNF1A–MODY group treated with sulphonylurea therapy alone improved significantly over the study period [from 49 (44–63) mmol/mol, 6.6 (6.2–7.9)% to 41 (31–50) mmol/mol, 5.9 (5–6.7)%; P = 0.003]. The rate of retinopathy was significantly lower than that noted in the Type 1 diabetes mellitus group (13.6 vs. 50%; P = 0.0001).There was also a lower rate of microalbuminuria and cardiovascular disease in the HNF1A–MODY group compared with the Type 1 diabetes mellitus group.

This study demonstrates that the majority of patients with HNF1A–MODY can be maintained successfully on sulphonylurea therapy with good glycaemic control. We note a significantly lower rate of micro‐ and macrovascular complications than reported previously. The use of appropriate therapy at early stages of the disorder may decrease the incidence of complications.