Diagnosis and Classification of Diabetes
- Diabetes is classified as type 1 (formerly called juvenile-onset or insulin-dependent diabetes mellitus), type 2 (formerly called adult-onset or non-insulin dependent diabetes mellitus), gestational or other specific types.
- Type 1 diabetes: complete or almost complete insulin deficiency, usually caused by autoimmunity. Clinical features: younger onset (usually but not always before 30 years old), normal body weight, usually no family history of diabetes, insulin treatment required immediately or within about a year, positive GAD, IA2 and/or islet cell antibodies, susceptibility to ketoacidosis and unstable blood glucose levels.
- Type 1b or idiopathic diabetes: an unusual form of phenotypic type 1 diabetes with almost complete insulin deficiency, a strong hereditary component, and no evidence of autoimmunity. Reported mainly in Africa and Asia.
- Latent autoimmune diabetes of adulthood (LADA): a form of type 1 diabetes with adult onset, slowly progressive, eventual insulin requirement but may respond to oral agents initially, usually no ketoacidosis on presentation, positive GAD, IA2 and/or islet cell antibodies.
- Type 2 diabetes: insulin resistance with preserved endogenous insulin secretion but inadequate to overcome the resistance. About 90-95% of all diabetes, more common type in ethnic minorities. Clinical features: older onset (often >35 years old, though recently occurring more often in youth), overweight or obese, strong family history of diabetes, response to oral agents usually for some years, and relatively stable blood glucose levels.
- At presentation, in the setting of acute illness, or as type 2 patients become increasingly insulin deficient, ketoacidosis may occur ("ketosis-prone type 2 diabetes").
- Gestational diabetes mellitus (GDM): diagnosed first during pregnancy. Usually a precursor to type 2, but may be first onset of type 1 diabetes.
- Other specific types of diabetes: those with a more well defined cause. Examples: post-pancreatectomy, Cushing’s syndrome, HIV-associated diabetes, cystic-fibrosis related diabetes, certain drugs such as glucocorticoids and genetic syndromes such as MODY, and infections such as coxsakievirus B.
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