Classification of Diabetes Mellitus Based on Underlying Cause

Type of Diabetes	Features
Type 1	absolute insulin deficiency following destruction of the beta-cells
Type 2	relative insulin deficiency due to a combination of insulin resistance and impaired insulin secretion
Gestational	diabetes triggered by pregnancy and often remitting afterwards
Other	genetic or acquired (see below)

 

Other causes of diabetes or impaired glucose handling due to genetic cause primarily affecting insulin production or action:

(1) genetic defect in beta-cell function

(1a) neuroD1 and chromosome 2 (MODY 6)

(1b) glucokinase and chromosome 7p (MODY 2)

(1c) HNF-1alpha and chromosome 12 (MODY 3)

(1d) insulin promotor factor 1 and chromosome 13 (MODY 4)

(1e) HNF-1beta and chromosome 17 (MODY 5)

(1f) HNF-4alpha and chromosome 20q (MODY 1)

(1g) mitochondrial DNA

(2) genetic defect in insulin action (defect in insulin receptor, etc)

(2a) Type A insulin resistance

(2b) leprechaunism

(2c) lipoatrophic diabetes

(2d) Rabson-Mendenhall syndrome)

 

Other causes of diabetes or impaired glucose handling due to acquired causes:

(1) disease of the exocrine pancreas

(1a) pancreatitis

(1b) cystic fibrosis

(1c) hemochromatosis

(1d) fibrocalculous pancreatopathy

(1e) pancreatic tumor

(1f) trauma or surgery

(2) drug or chemical-induced

(2a) corticosteroids

(2b) treatment of AIDS

(2c) organ transplantation (tacrolimus, other)

(2d) thiazides

(2e) interferon

(2f) Vacor

(2g) nicotinic acid

(2h) pentamidine

(2i) second-generation anti-psychotic agents

(2j) diazoxide

(2k) Dilantin

(2l) beta-adrenergic agonists

(2m) others

(3) endocrinopathies

(3a) acromegaly

(3b) glucagonoma or somatostatinoma

(3c) hyperthyroidism

(3d) aldosternoma or Cushing's disease

(3e) pheochromocytoma

(4) viral infection-related

(4a) cytomegalovirus (CMV)

(4b) congenital rubella

(5) immunologic disorders

(5a) antibodies to insulin receptor

(5b) stiff man syndrome

(6) hereditary disorder associated diabetes (may include one or more of the above mechanisms)

(6a) Klinefelter's syndrome

(6b) Turner's syndrome

(6c) Friedrich's ataxia

(6d) Wolfram's syndrome

(6e) Prader-Willi syndrome

(6f) Down's syndrome

(6g) myotonic dystrophy

(6h) Lawrence-Moon-Bardet-Biedl syndrome

(6i) congenital porphyria

(6j) others

 

Some patients have a syndrome that shares features of both Type 1 and Type 2 diabetes ("not quite Type 1, not quite Type 2").

 

Parameter	Type 1	Type 2	Not Quite
C-peptide	very low	higher	variable
autoantibodies	common	absent	variable
ketosis	prone	not prone	variable