Definition: Type 1 diabetes (T1D) is an autoimmune disorder characterized by the destruction of pancreatic β-cells, leading to absolute insulin deficiency.

• Etiology:
  • Autoimmune-mediated β-cell destruction (most common).
  • Idiopathic T1D: No known etiology, permanent insulinopenia, and DKA risk, but no autoimmunity (rare, <10% of cases).
• Clinical Features:
  • Classic symptoms: Polyuria, polydipsia, weight loss, fatigue.
  • Adult-onset T1D may present with milder symptoms and slower progression.
• Diagnosis:
  • Fasting plasma glucose ≥126 mg/dL, HbA1c ≥6.5%, or 2-h OGTT ≥200 mg/dL.
  • Autoantibodies (GADA, IA-2, ZnT8, islet cell antibodies) confirm autoimmune T1D.
• Management:
  • Lifelong insulin therapy (basal-bolus or premixed regimens).
  • Continuous glucose monitoring (CGM) and insulin pumps for glycemic control.
  • Screening for complications (retinopathy, nephropathy, neuropathy).
• Special Considerations:
  • Idiopathic T1D: Consider in cases with atypical features (e.g., no autoimmunity, stable mild hyperglycemia).
  • Monogenic diabetes (e.g., MODY) should be ruled out in cases with atypical presentation.

Rationale:

• Autoimmune T1D is the predominant form, diagnosed via autoantibodies and clinical criteria.
• Idiopathic T1D is a diagnosis of exclusion, requiring absence of autoimmunity and typical T1D features.
• Management focuses on insulin replacement and complication prevention, per ADA guidelines.