Diabetes Mellitus: Pathological Mechanisms
Diabetes Mellitus (DM) is a group of metabolic disorders characterized by chronic hyperglycemia resulting from defects in insulin secretion, insulin action, or both.
1. Type 1 vs. Type 2 Comparison
| Feature | Type 1 DM | Type 2 DM |
|---|---|---|
| Pathogenesis | Autoimmune destruction of beta cells (Type IV hypersensitivity). | Insulin resistance & progressive beta-cell dysfunction. |
| Pancreatic Histology | Insulitis (leukocyte infiltration of islets). | Amyloid deposits (islet amyloid polypeptide/amylin). |
| Genetics | HLA-DR3 and DR4. | Stronger polygenic/environmental association. |
2. Chronic Complications (Microvascular)
- Diabetic Nephropathy: Diffuse glomerulosclerosis and the classic Kimmelstiel-Wilson nodules (nodular glomerulosclerosis).
- Diabetic Retinopathy: Non-proliferative (hemorrhages, exudates, microaneurysms) and Proliferative (neovascularization due to VEGF).
- Diabetic Neuropathy: Osmotic damage via the polyol pathway (accumulation of sorbitol).
Pathology Board Hint: For board exams, always remember: Type 1 = insulitis, Type 2 = amyloid. If a question describes a kidney biopsy showing nodules in the glomerulus, it is classic for diabetic nephropathy (Kimmelstiel-Wilson).