What is type 1 diabetes?

Type 1 diabetes mellitus (T1DM) is a chronic disease characterized by hyperglycaemia secondary to absolute insulin deficiency. It is the result of T cell-mediated autoimmune destruction of the insulin-producing β-cells that reside in the islets of Langerhans. T1DM is associated with circulating autoantibodies to β-cell antigens. It results from an interplay between genetic and environmental factors. The autoimmune process can start in infancy, and the rate of autoimmune β-cell destruction varies widely between individuals. Therefore the disease has a variable duration of prodrome before the patient presents with symptoms of T1DM. The classic clinical presentation of T1DM is an acute onset of symptoms caused by rapid β-cell failure: weight loss, polyuria, polydipsia and risk of ketoacidosis. Although T1DM is the most common form of dysglycaemia in children and young adults, it can present at any age. Indeed, in some records 40% of cases present after age 30 years. The clinical presentation in adults can be less acute, and there is potential for diagnostic confusion. The long pre-clinical prodrome raises the possibility of intervention to delay or prevent the clinical onset of disease.