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Table 1. Etiologic Classification of Diabetes Mellitus
I. Type 1 diabetes (β-cell destruction, usually leading to absolute insulin deficiency)
A. Immune mediated
B. Idiopathic
II. Type 2 diabetes − a progressive insulin secretory defect on the background of
insulin resistance (may range from predominantly insulin resistance with relative
insulin deficiency to a predominantly secretory defect with insulin resistance)
III. Other specific types
A. Genetic defects of β-cell function
1. Chromosome 12,
HNF-1α (MODY3)
4. Chromosome 13, insulin promoter
factor-1 (IPF-1; MODY4)
7. Mitochondrial DNA
2. Chromosome 7,
glucokinase (MODY2)
5. Chromosome 17, HNF-1β
(MODY5)
8. Others
3. Chromosome 20,
HNF-4α (MODY1)
6. Chromosome 2, NeuroD1
(MODY6)
B. Genetic defects in insulin action
1. Type A insulin
resistance
3. Rabson-Mendenhall syndrome 5. Others
2. Leprechaunism 4. Lipoatrophic diabetes
C. Diseases of the exocrine pancreas
1. Pancreatitis 4. Cystic fibrosis 7. Others
2. Trauma/
pancreatectomy
5. Hemochromatosis
3. Neoplasia 6. Fibrocalculous pancreatopathy
D. Endocrinopathies
1. Acromegaly 4. Pheochromocytoma 7. Aldosteronoma
2. Cushing's syndrome 5. Hyperthyroidism 8. Others
3. Glucagonoma 6. Somatostatinoma
E. Drug or chemical induced
1. Vacor 5. yroid hormone 9. Dilantin
2. Pentamidine 6. Diazoxide 10. γ-Interferon
3. Nicotinic acid 7. β-adrenergic agonists 11. HIV/AIDS drugs
4. Glucocorticoids 8. iazides 12. Immune suppression
F. Infections
1. Congenital rubella 2. Cytomegalovirus 3. Others
G. Uncommon forms of immune-mediated diabetes
1. "Stiff-man" syndrome 2. Anti-insulin receptor antibodies 3. Others
H. Other genetic syndromes sometimes associated with diabetes
1. Down syndrome 5. Friedreich ataxia 9. Porphyria
2. Klinefelter syndrome 6. Huntington chorea 10. Prader-Willi
syndrome
3. Turner syndrome 7. Laurence-Moon-Biedl syndrome 11. Others
4. Wolfram syndrome 8. Myotonic dystrophy
IV. Gestational diabetes mellitus (GDM) (first diagnosed during pregnancy and
clearly not overt diabetes)
