Diabetes Mellitus - Type I

Overview
  • Type I Diabetes Mellitus (Type I DM) was originally termed "Juvenile Diabetes" because it largely presented in adolescents and young adults. However, this term is no longer in use as the age of Type II DM onset has progressively decreased and has come to overlap with that of Type I DM.
Etiology
  • Type I DM is an autoimmune disease which results in progressive immune-mediated destructions of the Islets of Langerhans, ultimately leading to deficiencies in insulin synthesis. Development of the disease appears to occur in individuals with some genetic susceptibility who undergo a unidentified environmental insult. Those possessing HLA-DR4 and HLA-DR3 alleles are at increased risk and some theorize that a cryptic viral infection may be the source of the environmental insult.
Pathogenesis
  • Whatever the ultimate etiology, Type I DM is characterized by lymphocytic infiltration of the endocrine pancreas specifically in the Islets of Langerhans. This inflammatory infiltration, termed Insulinitis, appears to be primarily composed of T-cells and can be observed years before clinical onset. Inflammation leads to progressive and selective destruction of insulin-producing islet beta cells. Clinically apparent diabetes begins only after nearly all (~80%) of pancreatic beta cells have been destroyed. Once this physiological reserve of beta cells has been destroyed, insulin levels progressively decline and may reach complete absence.
Clinical Consequences
Treatment
  • Type I DM is treated with lifetime recombinant insulin replacement therapy.