Maturity onset diabetes of the young
| Maturity onset diabetes of the young | |
| OMIM | 606391 |
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| DiseasesDB | 8330 |
| MeSH | D003924 |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: MODY;
Signs, symptoms and differential diagnosis
There are two general types of clinical presentation. Some forms of MODY produce significant hyperglycemia and the typical signs and symptoms of diabetes: increased thirst and urination (polydipsia and polyuria). In contrast, however, many people with MODY have no signs or symptoms and are diagnosed by either accident, when a high glucose is discovered during testing for other reasons, or screening of relatives of a person discovered to have diabetes. Discovery of mild hyperglycemia during a routine glucose tolerance test for pregnancy is particularly characteristic.
MODY cases may make up as many as 5% of presumed type 1 and type 2 diabetes cases in a large clinic population. While the goals of diabetes management are the same no matter what type, there are two primary advantages of confirming a diagnosis of MODY. Firstly, insulin may not be necessary and it may be possible to switch a person from insulin injections to oral agents without loss of glycemic control. Secondly, it may prompt screening of relatives and so help identify other cases in family members.
As it occurs infrequently, many cases of MODY are initially assumed to be more common forms of diabetes: type 1 if the patient is young and not overweight, type 2 if the patient is overweight, or gestational diabetes if the patient is pregnant. Standard diabetes treatments (insulin for type 1 and gestational diabetes, and oral hypoglycemic agents for type 2) are often initiated before the doctor suspects a more unusual form of diabetes. In some forms of MODY, standard treatment is appropriate, though exceptions occur. For example, in MODY2, oral agents are relatively ineffective and insulin is unnecessary, while in MODY1 and MODY3, insulin may be more effective than drugs to increase insulin sensitivity. Sulfonylureas are effective in the KATP channel forms of neonatal-onset diabetes.
The following characteristics suggest the possibility of a diagnosis of MODY in hyperglycemic and diabetic patients:
- Mild to moderate hyperglycemia (typically 130-250 mg/dl, or 7-14 mM) discovered before 30 years of age.
- A first degree relative with a similar degree of diabetes.
- Absence of positive antibodies or other autoimmunity (e.g., thyroiditis) in patient and family.
- Persistence of a low insulin requirement (e.g., less than 0.5 u/kg/day) past the usual "honeymoon" period.
- Absence of obesity (though obese people can get MODY), or other problems associated with type 2 diabetes or metabolic syndrome (e.g. hypertension, hyperlipidemia, polycystic ovary syndrome).
- Cystic kidney disease in patient or close relatives.
- Non-transient neonatal diabetes, or apparent type 1 diabetes with onset before 6 months of age.
The diagnosis of MODY is confirmed by specific gene testing, now available through several commercial laboratories.
Management
Unfortunately, chronic hyperglycemia of any cause can eventually cause blood vessel damage and the microvascular complications of diabetes. The principal treatment goals for people with MODY — keeping the blood sugars as close to normal as possible ("good glycemic control"), while minimizing other vascular risk factors — are the same for all known forms of diabetes.
Tools available for management are also those available for all forms of diabetes: blood testing, changes in diet, physical exercise, oral hypoglycemic agents, and insulin injections. In many cases these goals can be achieved more easily with MODY than with ordinary types 1 and 2 diabetes. Some people with MODY may require insulin injections to achieve the same glycemic control that another person may attain with careful eating or an oral medication.
When oral hypoglycemic agents are used in MODY, the sulfonylureas remain the oral medication of first resort. Patients with MODY less often suffer from obesity and insulin resistance than those with ordinary type 2 diabetes (for whom insulin sensitizers like metformin or the thiazolidinediones are often preferred over the sulfonylureas).
References
Further reading
- Fajans SS (1990). "Scope and heterogeneous nature of MODY". Diabetes Care. 13 (1): 49–64. doi:10.2337/diacare.13.1.49. PMID 2404717. (For historical perspective, this review covers the concept just before the nature of the first of the specific molecular defects was discovered. It illustrates the significant change in the disease(s) referred to as MODY before and after 1990.)
- Fajans SS, Bell GI, Polonsky KS (2001). "Molecular mechanisms and clinical pathophysiology of maturity-onset diabetes of the young". N. Engl. J. Med. 345 (13): 971–80. doi:10.1056/NEJMra002168. PMID 11575290. (An excellent overview of the modern concept of the 6 types of MODY.)
- Dean L and McEntyre J, 2004. The Genetic Landscape of Diabetes. Bethesda:NCBI, 2004. This is an entire online textbook on the complex genetics of the forms of diabetes. The chapter on MODY provides an up-to-date and concise overview of the molecular defects. Little expansion of clinical knowledge of the 6 types since 2001 has occurred.
External links
- Andrew Hattersley's Exeter and Oxford research groups
- Virtual Grand Rounds: "MODY" by William E. Winter