ESSENTIALS OF DIAGNOSIS & TYPICAL FEATURES
Polyuria, polydipsia, and weight loss; respiratory distress, heavy diapers in infants.
Hyperglycemia and glucosuria often with ketonemia/ketonuria.
Type 1 diabetes (T1D) is the most common type of diabetes mellitus in people younger than 20 years, but can develop at any age and most cases are diagnosed after age 20. The classical presentation includes increased thirst (polydipsia), 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. T1a diabetes is marked by the presence of autoantibodies to islet cell autoantigens (insulin, GAD65, IA-2, and ZnT8) and high-risk HLA (human leucocyte antigen) haplotypes (DR4-DQ8, and DR3-DQ2). Insulin production, measured by fasting or stimulated C-peptide levels, is usually low. In the United States, T1D affects an estimated 1.5 million people, including more than 200,000 patients younger than age 20 (~25,000 diagnosed annually).
Type 2 diabetes (T2D) is a heterogeneous phenotype diagnosed most often in persons older than age 40 who are usually obese and initially not insulin-dependent. T2D is rare before age 10, but has increased in frequency in older children as a consequence of the epidemic of obesity. The vast majority of the 29 million patients with diabetes in the United States have T2D, but less than 20,000 patients are younger than age 20 (~5000 diagnosed annually).
Monogenic Forms of Diabetes
Monogenic forms of diabetes can be diagnosed 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. All children diagnosed with diabetes in the first 6 months of life should have genetic screening for neonatal diabetes. Neonatal diabetes is transient in about 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 services are available to aid correct diagnosis.
Cystic Fibrosis-Related Diabetes
Cystic fibrosis-related diabetes (CFRD) occurs in about 20% of adolescents with cystic fibrosis and is the most common comorbidity in cystic fibrosis. The primary defect is insulin insufficiency, exacerbated by insulin resistance especially in times of illness or with glucocorticoid therapy. The presence of CFRD is associated with worse nutritional status, ...