Diabetes Mellitus, Type I



Type 1 diabetes is an autoimmune disorder that causes pancreatic β-cell destruction. This destruction leads to insulin deficiency that results in hyperglycemia and disrupts energy storage and metabolism. Severe insulin deficiency can lead to ketosis, acidosis, dehydration, shock, and death.


  • Most common endocrine disorder of childhood
  • More common in whites of Northern European descent


  • Annual U.S. incidence is <19/100,000 in children 10 to 19 years old.
  • Incidence of type 1 diabetes is rising by 3% per year overall and faster in young children.


  • Prevalence of type 1 diabetes in youth 0 to 19 years in United States is <2/1,000.
  • Note: At least 2% of diabetes in children may be due to maturity-onset diabetes of youth (MODY) or other genetic forms.

Risk Factors


  • Increased susceptibility to type 1 diabetes associated with HLA region of chromosome 6, 5-fold greater risk with MHC antigen types DR3 and DR4
  • MODY is a group of autosomal dominant syndromes of partial insulin deficiency due to monogenic defects of pancreatic development or insulin secretion; they comprise a small fraction of childhood diabetes.


  • Loss of pancreatic β cells results in insulin deficiency, leading to hyperglycemia and predominance of catabolic processes.
  • Hyperglycemia causes hyperosmolality, polyuria, and damage to small blood vessels.
  • Catabolic processes produce ketosis, weight loss, and metabolic acidosis.


  • An environmental trigger (likely viral) induces expression of antigens on β-cell surface.
  • Recruitment of cytotoxic lymphocytes
  • Production of anti-insulin and anti-islet cell anti-bodies (including GAD65, ICA512, ZnT8)
  • Progressive inflammatory, autoimmune loss of β-cell mass results in insulin deficiency.
  • Autoimmunity precedes hyperglycemia; development of two or more antibodies will inevitably lead to dysglycemia due to type 1 diabetes.
  • The autoimmune destruction of β cells is more likely in genetically susceptible persons.

Commonly Associated Conditions

  • Autoimmune thyroid disease
    • Hashimoto (hypothyroidism) more common than Graves (hyperthyroidism)
  • Celiac disease
  • More rarely other autoimmune diseases, such as alopecia areata, rheumatoid arthritis
  • Depression
  • After prolonged hyperglycemia: vascular complications:
    • Microvascular
      • Nephropathy
      • Retinopathy
      • Neuropathy
      • (See “Patient Monitoring” for screening recommendations.)
    • Macrovascular
      • Peripheral vascular disease
      • Cardiovascular disease

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