Diabetes mellitus type 1 Classification

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Vishal Devarkonda, M.B.B.S[2]Anahita Deylamsalehi, M.D.[3]

According to American Diabetic Association (ADA), type 1 DM could be classified based on both etiology and clinical presentations. Based on etiology type 1 DM can be classified into immune mediated or idiopathic. Nevertheless classic new onset diabetes mellitus and Diabetic ketoacidosis are considered two classes of diabetes mellitus type 1 based on clinical presentations.

• Based on etiology, American diabetic association has classified type 1 DM into:^[1]
  • Immune-mediated
  • Idiopathic
• Based on clinical presentation, Type 1 DM can be classified into:^[2]
  • Classic new onset diabetes mellitus
  • Diabetic ketoacidosis
• Some studies proposed a new subtype of diabetes mellitus type 1. The following are some features of this subtype:^[3][4]
  • There is no relationship to autoimmune conditions, evidenced by absence of any diabetes mellitus type 1 related autoantibodies, such as Glutamate decarboxylase, islet-cell, IA-2, or insulin antibodies.
  • Pancreatic biopsies revealed neither insulitis nor hyperexpression of MHC class I molecules as it is expected in diabetes mellitus type 1. In the contrary lymphocytic infiltrates were reported in the exocrine pancreas.
  • With a rapid onset, only few days after hyperglycemic symptoms (mean duration of four days) patients were diagnosed with diabetic ketoacidosis. The short period of hyperglycemia is evidenced by normal HbA1C in these patients.
  • The study demonstrated that this group has low insulin secretion, which is further supported by a low C-peptide urinary excretion.
  • In contrast to other diabetes mellitus type 1 patients with normal serum pancreatic enzyme concentrations and evidences of insulinitis, this subtype is presented with noticeably elevated pancreatic enzyme level and lymphocytic infiltrates in the exocrine pancreas.

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