DM is classified on the basis of the pathogenic process that leads to hyperglycemia, as opposed to earlier criteria such as age of onset or type of therapy. The two broad categories of DM are designated type 1 and type 2. Both types of diabetes are preceded by a phase of abnormal glucose homeostasis as the pathogenic processes progresses. Type 1 diabetes is the result of complete or near-total insulin deficiency. Type 2 DM is a heterogeneous group of disorders characterized by variable degrees of insulin resistance, impaired insulin secretion, and increased glucose production.
I. Type 1 diabetes (cell destruction, usually leading to absolute insulin deficiency)
- A. Immune-mediated
- B. Idiopathic
II. Type 2 diabetes
- may range from predominantly insulin resistance with relative insulin deficiency to a predominantly insulin secretory defect with insulin resistance
III. Other specific types of diabetes
A. Genetic defects of cell function characterized by mutations in:
- 1. Hepatocyte nuclear transcription factor (HNF) 4 (MODY 1)
- 2. Glucokinase (MODY 2)
- 3. HNF-1 (MODY 3)
- 4. Insulin promoter factor-1 (IPF-1; MODY 4)
- 5. HNF-1 (MODY 5)
- 6. NeuroD1 (MODY 6)
- 7. Mitochondrial DNA
- 8. Subunits of ATP-sensitive potassium channel
- 9. Proinsulin or insulin conversion
B. Genetic defects in insulin action
- 1. Type A insulin resistance
- 2. Leprechaunism
- 3. Rabson-Mendenhall syndrome
- 4. Lipodystrophy syndromes
C. Diseases of the exocrine pancreas
- pancreatitis,
- pancreatectomy,
- neoplasia,
- cystic fibrosis,
- hemochromatosis,
- fibrocalculous pancreatopathy,
- mutations in carboxyl ester lipase
D. Endocrinopathies
- acromegaly,
- Cushing's syndrome,
- glucagonoma,
- pheochromocytoma,
- hyperthyroidism,
- somatostatinoma,
- aldosteronoma
E. Drug-induced or chemical-induced
- vacor,
- pentamidine,
- nicotinic acid,
- glucocorticoids,
- thyroid hormone,
- diazoxide,
- beta-adrenergic agonists,
- thiazides,
- phenytoin,
- alpha-interferon,
- protease inhibitors,
- clozapine
F. Infections
- congenital rubella,
- cytomegalovirus,
- coxsackie
G. Uncommon forms of immune-mediated diabetes
- "stiff-person" syndrome,
- anti-insulin receptor antibodies
H. Other genetic syndromes sometimes associated with diabetes
- Down's syndrome,
- Klinefelter's syndrome,
- Turner's syndrome,
- Wolfram's syndrome,
- Friedreich's ataxia,
- Huntington's chorea,
- Laurence-Moon-Biedl syndrome,
- myotonic dystrophy,
- porphyria,
- Prader-Willi syndrome
IV. Gestational diabetes mellitus (GDM)