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ESSENTIALS OF DIAGNOSIS & TYPICAL FEATURES
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ESSENTIALS OF DIAGNOSIS & TYPICAL FEATURES
Polyuria, polydipsia, and weight loss; respiratory distress, heavy diapers in infants.
Hyperglycemia and glucosuria, often with ketonemia/ketonuria at presentation.
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Epidemiology & Description
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Type 1 diabetes (T1D) is the most common type of diabetes mellitus in people younger than 20 years, but it can develop at any age and most cases are diagnosed after age 20. The classical presentation includes increased thirst (polydipsia), increased urination (polyuria), and weight loss; however, the patient may be overweight or even obese. T1D is further divided into T1a (autoimmune) (~ 95% of the cases) and T1b (idiopathic) diabetes. T1b is more common in individuals of African or Asian ancestry. In the United States, T1D affects an estimated 1.5 million people, including more than 200,000 patients younger than 20 (~ 25,000 diagnosed annually).
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T1D incidence is the highest in children of European ancestry, followed by African Americans and Hispanics; rates are low in Asians and Native Americans. About 6% of siblings or offspring of persons with T1D also develop diabetes (compared with prevalence in the general population of 0.2%–0.3%). However, fewer than 10% of children newly diagnosed with T1D have a parent or sibling with the disease.
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Type 2 diabetes (T2D) is a heterogeneous phenotype diagnosed most often in persons older than 40 who are usually obese and initially not insulin dependent. T2D is rare before age 10; however, puberty is a time of heightened risk for development of T2D in susceptible individuals. Due to the epidemic of childhood obesity, T2D has increased in frequency in older children. T2D is more common in youth of ethnic and racial minorities, particularly the native American population. Other risk factors include female sex, poor diet and sleep, and low socioeconomic status. The vast majority of the 30 million patients with diabetes in the United States have T2D, but less than 20,000 patients are younger than 20 (~ 5000 diagnosed annually).
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C. Monogenic Forms of Diabetes
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Monogenic forms of diabetes can be diagnosed at any age. They account for less than 1% of childhood diabetes, but form the majority of cases diagnosed before the ninth month of life. Neonatal diabetes is transient in about one-half of the cases; if persistent, it presents a significant clinical challenge and requires subspecialty care. Some infants respond better to sulfonylurea than insulin. Maturity-onset diabetes of the young (MODY) presents as a nonketotic and usually non–insulin-dependent diabetes in the absence of obesity or islet autoantibodies. A strong family history of early-onset diabetes is common. The most frequent forms are due to mutations in glucokinase or hepatic nuclear factor 1 or 2 genes. Glucokinase mutations rarely require therapy; other forms respond to oral hypoglycemic agents or insulin. Commercial and research-oriented genotyping ...