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Maturity Onset Diabetes of the Young (MODY)

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What is MODY?

Maturity Onset Diabetes of the Young (MODY) is a group of diabetes disorders that affects about 2% of people with diabetes. MODY is often not recognized and people may be treated as though they have type 1 or type 2 diabetes by their doctors. MODY has four main characteristics:

  • Diabetes presents at a young age, usually less than 25 years of age.
  • MODY runs in families through several generations. A parent with MODY has a 50% chance of passing on MODY to their child. This is called autosomal dominant inheritance.
  • People with MODY do not always need insulin treatment and can often be treated with diabetes pills or meal planning alone.
  • People with MODY do not produce enough insulin; this is different to type 2 diabetes where people frequently produce lots of insulin but don't respond to their insulin.
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Why is MODY Important?

MODY was first described by Tattersall (U.K.) and Fajan (U.S.A.) in 1974, after they had noticed a group of young people with diabetes who were treated without insulin 2 years or more after diagnosis. Since the 1970s there has been great interest in MODY as it is a genetic form of diabetes. Each type of MODY is caused by a single gene not working correctly whereas type 2 diabetes seems to be caused by minor problems in several genes at once. By studying MODY genes, scientists can get insights into the mechanisms causing all types of diabetes and potential treatments for diabetes.

The first MODY gene was found in 1992 (5), and there are now six known genes in which defects will cause MODY (4). These genes are for the body's glucose sensor (glucokinase), and five transcription factors that control the way insulin is produced from the beta cells of the pancreas (HNF-1 alpha, HNF-1 beta, HNF-4alpha, IPF-1, and NEURO-D1). These six genes each produce slightly different forms of diabetes.

MODY mutations have been found in many different ethnic groups, with glucokinase and HNF-1 alpha being the commonest types by far. In total MODY makes up between 2-5% of patients with non-type 1 diabetes. 15% of MODY patients will not have a known MODY mutation; these people are said to have MODY X, and work is continuing to find the gene disorders responsible (3, 4).

Varieties of MODY:

  • MODY 1 (HNF-4?) Rare form of MODY. Similar effects to MODY 3.
  • MODY 2 (Glucokinase) Causes between 10-65% of MODY. Causes mild diabetes that rarely causes complications. Can often be treated with meal planning alone. Often diagnosed in childhood or pregnancy.
  • MODY 3 (HNF-1 alpha) Causes between 20-75% of MODY. Causes progressive diabetes and patients may get diabetes complications. Usually diagnosed after puberty. Sensitive to sulfonylurea drugs.
  • MODY 4 (IPF-1) Rare form of MODY. Seems to produce relatively mild diabetes.
  • MODY 5 (HNF-1 beta) Rare form of MODY. Associated with kidney disease that is often diagnosed before diabetes.
  • MODY 6 (Neuro- D1) Extremely rare form of MODY. Severity of diabetes unknown as yet.

Do I have MODY?

You might have MODY if:

  • you have a strong history of diabetes in your family;
  • you developed diabetes before middle age;
  • you are not overweight;
  • and you are treated on meal planning alone, diabetes pills or on low doses of insulin (less than 0.5 units of insulin per Kg of body weight) more than 18 months after you were diagnosed with diabetes.
References
  1. Mild familial diabetes with dominant inheritance Tattersal RB. Quarterly Journal of Medicine 1974; 43:339-357
  2. A difference between the inheritance of classical juvenile-onset and maturity-onset type diabetes of young people Tattersall RB, Fajans SS. Diabetes 1975 Jan;24(1):44-53
  3. Molecular Genetics of Maturity-onset Diabetes of the Young Froguel P, Velho G. Trends Endocrinol Metab. 1999; 10(4):142-146
  4. Molecular mechanisms and Clinical Pathophysiology of Maturity Onset Diabetes of the Young Fajans S, Bell G, Polonsky K. N. Engl. J. Med. 2001; 345(13):971-980
  5. Linkage of type 2 diabetes to the glucokinase gene Hattersley AT, Turner RC, Permutt MA, Patel P, Tanizawa Y, Chiu KC, O'Rahilly S, Watkins PJ, Wainscoat JS. Lancet 1992;339(8805):1307-10
  6. Beta Cell Genes and Diabetes; Molecular and Clinical Characterization of Mutations in Transcription Factors Frayling TM, Evans JC, Bulman MP, Pearson E, Allen L, Owen K, Bingham C, Hannemann M, Shepherd M, Ellard S, Hattersley AT. Diabetes 2001;50(Suppl. 1):S94-100
  7. Diagnosis and management of maturity-onset diabetes of the young Timsit J, Bellanne-Chantelot C, Dubois-Laforgue D, Velho G. Treat Endocrinol. 2005;4(1):9-18.
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