Although insulin was discovered more than a century ago and its role in the etiopathogenesis of diabetes mellitus is well known.1 However, it was not until 2008 that mutations in the gene encoding insulin were first identified as the cause of permanent neonatal diabetes.2 In the last decade, the number and type of mutations identified have been increasing, allowing the study of new diagnostic and therapeutic perspectives for this type of monogenic diabetes.3

The aim of the present study was to describe the clinical expression of a family diagnosed with diabetes due to a dominant mutation in the insulin gene, as well as its evolution over time and its response to different treatments during follow-up in the Paediatrics and Endocrinology and Nutrition Departments of a tertiary hospital.