Other specific types of diabetes

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Gene defects
Specific genetic/molecular defects have been identified in a minority of what were considered type 2 diabetes:

Mitochrondial Syndromes:
Maternally inherited.
• DIDMOAD (Wolfam syndrome) – Diabetes Insipidus, Diabetes Mellitus, Optic Atrophy, sensorineural Deafness; inherited progressive neurodegenerative disease; abnormalities in mitochrondial DNA have been identified
• mitochrondial DNA mutations account for <1% of diabetes cases; families have been described in the literature in which transmission of type two diabetes associated with deafness Maturity onset diabetes of the young (MODY): Uncommon cause of type 2 diabetes (1-5% of cases in western countries); autosomal dominant; <25 years; dysfunction is in beta cell secretion of insulin; environmental factors not involved; not obese; several subtypes have been identified – MODY 1 (mutation in gene that encodes for hepatic nuclear factor 4-alpha), MODY 2 (mutation in gene that encodes for B-cell enzyme glucokinase), MODY 3 (mutation in gene that encodes for hepatic nuclear factor 1-alpha; most common type), MODY 4 (mutation in insulin promoter gene, MODY 5 (others); Name (MODY) is from the time when diabetes was classified based on age of onset Incidence of diabetes mellitus is higher in a number of inherited conditions: eg Down syndrome, Turner syndrome, Freidreichs ataxia, Huntington’s chorea, Porphyria, Prader-Willi syndrome, Klinfelter’s syndrome, myotonic dystrophy Cystic fibrosis related diabetes (CFRD): Pancreatic disease is common in cystic fibrosis. Insulin resistance does not appear to play a role. Endocrine disorders 1) Diseases of the pancreas (account <1% of diabetes) acute pancreatitis – often may need insulin for hyperglycaemia chronic pancreatitis – can be complicated by development of diabetes (further complicated due to alcoholism) pancreatomy – will need insulin if large amount of pancreas is removed pancreatic carcinoma (on rare occasions diabetes can be presently feature) haemochromatosis – half develop diabetes that usually needs insulin; has been called ‘bronzed diabetes’ from melanin deposits in skin 2) Endocrinopathies Excessive secretion of counter-regulatory hormones are associated with the development of glucose intolerance/diabetes: • Graves disease – • Acromegaly – 30% have glucose intolerance; 30% have diabetes • Cushing’s syndrome – post-receptor insulin resistance develops from excessive ACTH secretion Coeliac disease/gluten enteropathy: • Prevalence of 1-16% of children with diabetes • May develop hypoglycaemia due to the malabsorption of glucose. • May be diagnosed in Type one who have mild and abdominal symptoms Malnutrition related diabetes Rare; ketosis resistant. In tropics where protein malnutrition is common. Usually aged 15-30 years at presentation; low body weight Subtypes – ‘fibrocalculous diabetes’ and ‘protein deficient pancreatic diabetes’ Some need very high doses of insulin. Drug/chemical induced A number of drugs are associated with development of glucose intolerance/diabetes or the deterioration of blood glucose controls in those with diabetes: • corticosteroids – may precipitate diabetes in those at risk; high doses usually needed; mechanism thought to be due to post-receptor insulin resistance • beta-blockers – those with hypertension often have other features of the insulin resistance syndrome; metabolic effects of beta-blockers may precipitate diabetes, but the therapeutic goal of reducing blood pressure may outweigh risk • diuretics (especially high dose thiazides) – may affect insulin resistance and insulin secretion • oral contraceptives – have minor metazoic effects that may slightly increase risk for diabetes • immunosuppression – cyclosporine is associated with insulin resistance and toxicity to the beta cells; may be exacerbated if corticosteroid also being used Infection eg congenital rubella, cytomegalo virus Immune mediated (uncommon) eg Stiff man syndrome, anti-insulin receptor antibodies Stiff man Syndrome: Develop spastic paresis; involvement of numerous endocrine glands are common; 30% have type 1 diabetes

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