A good metabolic control of type 1 diabetes mellitus (T1DM) is crucial to avoid long-term complications associated with the disease. Although recent evidences suggest that a good metabolic control of T1DM is partly independent of management intensity and could be anticipated since onset, factors that influence glycated haemoglobin (HbA1c) patterns remain poorly understood and are likely to be genetic. While significant progress has been made in understanding of the genetic contribution to T1DM onset, very few studies have evaluated the role of genetic factors on T1DM metabolic control. This study aims to create a comprehensive database of genetic and phenotypic data in a cohort of children and young adults with T1DM and to evaluate genetic and environmental factors that might predict trajectories in glycemic control