Maturity onset diabetes of the young
Overview
Maturity-onset diabetes of the young (MODY) is an uncommon form of diabetes that is caused by a genetic defect inherited from either parent. It is sometimes considered a subgroup of type 2 diabetes but differs in several ways from the standard form of that disease. It can also be misdiagnosed as type 1 diabetes or other forms of diabetes. MODY is most often diagnosed in teens or young adults of normal weight and build. It is sometimes seen in children as young as 6 years old. Several genetic defects have been identified in MODY patients. Of the eight known types of MODY, most can be controlled by diet alone or through antidiabetic agents. However, certain types of MODY require insulin therapy. The offspring of a person with MODY have a 50 percent risk of developing the condition. Because of this, MODY is often present in at least two generations of a patient’s family.
Symptoms
* Excessive thirst (polydipsia) * Frequent urination (polyuria) * Fatigue * Unexplained weight loss * Frequent infections, including persistent vaginal infections in women, skin infections and gingivitis (gum disease)
Causes
The causes of the various types of maturity-onset diabetes of the young (MODY) have been traced back to defects at the molecular level of several different genes. Diagnosis of MODY thus can involve genetic testing. The children of a person with MODY have a 50 percent chance of developing this uncommon form of diabetes. As a comparison, the children of a person with type 2 diabetes have a 1-in-7 chance of developing type 2 diabetes if the parent was diagnosed before the age of 50 and a 1-in-13 chance if their parent was diagnosed after age 50, according to the American Diabetes Association. The first MODY gene was discovered in 1992. Scientists continue to identify additional genes. Some cases of MODY involve a gene that has not yet been implicated. It is believed that as many as 10 to 12 genes play a role in the development of MODY. Race, ethnicity and nationality may be risk factors for MODY. Some researchers have reported an above-normal prevalence in black Americans and in Romanians. In addition, many cases of MODY in Chinese and Japanese patients are reported to be caused by genes that have not yet been identified.
Diagnosis
A proper diagnosis of diabetes can involve a variety of lab tests, including any of three glucose tests: * Random glucose * Fasting glucose * Oral glucose tolerance test (OGTT) Because a single positive test is not enough to confirm a diagnosis of diabetes, a series of tests may be conducted over time. In addition to these basic diabetes tests, a diagnosis of maturity-onset diabetes of the young (MODY) involves: * A thorough review of the patient’s clinical treatment to date and its effectiveness. * Evaluation of the severity of hyperglycemia. Young patients who develop MODY3 often exhibit markedly high glucose (blood sugar) and may be mistaken for having type 1 diabetes. * The patient’s family history. MODY is often diagnosed in a family where one member has been diagnosed before the age of 25. The pattern of inheritance of diabetes can therefore be identified within the family. * A comparison with the four main characteristics of MODY. * Genetic testing to determine the gene defect causing the disease. This blood test involves examining a sample to determine if the patient’s DNA contains a genetic mutation consistent with MODY, especially if it is the same genetic mutation as that of a diagnosed relative. It is possible to be genetically tested if parents or other family members have not undergone testing. Test results are normally available within four to eight weeks, depending on the genetics laboratory. MODY can be mistakenly diagnosed as type 1, type 2 diabetes or another form of diabetes, such as latent autoimmune diabetes of adulthood (LADA). Misdiagnosis is more likely when the patient does not have the body type or age expected for the diagnosis. For instance, a person under age 25 with a slender build does not fit the typical profile of type 2 diabetes. Children of parents with MODY are most often diagnosed through genetic testing even before symptoms occur. Early intervention, in turn, allows physicians to offer guidance to prevent or delay the onset of the disease. A positive genetic blood test result indicates the genetic mutation has been inherited from a family member with diabetes. With a positive result, yearly blood glucose evaluations are highly recommended. So far at least eight types of MODY have been identified. The type of MODY for each patient should be determined, if possible, because treatment options vary depending on the type.
Treatment
The diagnosis and treatment of diabetes is not always straightforward, particularly with lesser-known forms of the disease, such as maturity-onset diabetes of the young (MODY). Treatment depends mainly on the variety of MODY with which a patient is diagnosed. These forms of diabetes require treatment plans tailored to suit the needs of the individual. Like type 2 diabetes, certain forms of MODY can be controlled primarily through diet and exercise, at least in the early stages. Other forms of this disease may require antidiabetic agents or insulin administration. There are important distinctions among the eight known forms of MODY. Testing can help establish the appropriate treatment protocol. The physician will establish a target glucose (blood sugar) range and a schedule of home glucose monitoring, other self-testing if needed (e.g., ketone tests), foot care and skin care. There will also be a schedule of medical appointments for physical examinations, complete foot exams, blood tests such as the glycohemoglobin test of glucose control and urine tests such as the microalbuminuria test of kidney function. The physician can create a sick-day plan to help keep illnesses from disrupting metabolic control. Patients can be referred to a certified diabetes educator and registered dietitian for assistance in managing their condition. They should go to an ophthalmologist for regular eye exams and have regular dental care to reduce their increased risk of gum disease. Patients needing antidiabetic agents may be prescribed sulfonylureas or other drug categories or combinations. Choice for insulin-dependent MODY patients may include syringe injections, insulin pens or insulin pumps. In its approval of inhaled insulin in 2006, the U.S. Food and Drug Administration (FDA) specified adult nonsmokers with type 1 diabetes or type 2 diabetes, so it is not clear whether adults with MODY may qualify. An islet cell transplant may be an option for some MODY patients, although the procedure is still considered experimental.As with other forms of diabetes, lifestyle changes (quitting smoking, good nutrition, physical activity) can delay or help control the disease. There are no known ways to prevent the onset of MODY. If the disease has been inherited (and confirmed through genetic testing), the chances of developing MODY are nearly 100 percent. Initially, physicians found little evidence of typical diabetic complications from MODY, particularly microvascular problems, including the kidney disease diabetic nephropathy and the eye disease diabetic retinopathy. However, it is now believed that certain forms of MODY can indeed lead to these complications, and physicians recommend controlling cholesterol and blood pressure as well as glucose.