WHAT IS DIABETES MELLITUS?

Diabetes mellitus is a disease caused by deficiency or diminished effectiveness of endogenous insulin. It is characterised by hyperglycaemia, deranged metabolism and sequelae predominantly affecting the vasculature. The main types of diabetes mellitus are:

• Type 1 diabetes mellitus: results from the body's failure to produce sufficient insulin.
• Type 2 diabetes mellitus: results from resistance to the insulin, often initially with normal or increased levels of circulating insulin.
• Gestational diabetes: pregnant women who have never had diabetes before but who have high blood glucose levels during pregnancy are said to have gestational diabetes. Gestational diabetes affects about 4% of all pregnant women. It may precede development of type 2 (or rarely type 1) diabetes.
• Maturity-onset diabetes of the young (MODY) includes several forms of diabetes with monogenetic defects of beta-cell function (impaired insulin secretion), usually manifesting as mild hyperglycaemia at a young age, and usually inherited in an autosomal-dominant manner.^[1]
• Secondary diabetes: accounts for only 1-2% of patients with diabetes mellitus. Causes include:
• Pancreatic disease: cystic fibrosis, chronic pancreatitis, pancreatectomy, carcinoma of the pancreas.
• Endocrine: Cushing's syndrome, acromegaly, thyrotoxicosis, phaeochromocytoma, glucagonoma.
• Drug-induced: thiazide diuretics, corticosteroids, atypical antipsychotics, antiretroviral protease inhibitors.
• Congenital lipodystrophy.
• Acanthosis nigricans.
• Genetic: Wolfram's syndrome (which is also referred to as DIDMOAD: diabetes insipidus, diabetes mellitus, optic atrophy and deafness),^[2] Friedreich's ataxia, dystrophia myotonica, haemochromatosis, glycogen storage diseases.

Some patients with type 2 diabetes require insulin, so the old terms of insulin-dependent diabetes mellitus (IDDM) for type 1 diabetes and non-insulin-dependent diabetes mellitus (NIDDM) for type 2 diabetes are inappropriate. 

Type 2 diabetes is increasingly diagnosed in children and adolescents and so the old term maturity-onset diabetes for type 2 diabetes is also inappropriate.

Article taken from http://www.patient.co.uk/doctor/diabetes-mellitus

References:

1)       Maturity-onset Diabetes of The Young, Online Mendelian Inheritance in Man (OMIM)

2)       Wolfram Syndrome 1, WFS1; Online Mendelian Inheritance in Man (OMIM)