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Diabetes mellitus (DM) is a major cause of morbidity and mortality in the United States. More than 24 million Americans have the disease1, and approximately 11% ($92 billion) of all health care expenditures in the United States were directly attributable to the medical care of diabetes in 2002.2 Men and women diagnosed with diabetes at age 40 years are expected to lose 12 and 14 life-years, respectively.3 Major studies have shown that tight glycemic control decreases microvascular disease, i.e., retinopathy, neuropathy, nephropathy, however, coronary vascular disease, the major contributor to morbidity and mortality in patients with diabetes, showed no benefit from intensive glycemic control for patients with a known 10-year duration of diabetes. In one large randomized controlled trial with about a third of patients with known coronary artery disease, intensive glycemic control was, in fact, associated with an increase in mortality. Newly diagnosed type 2 diabetes appears to have long-term benefit from similar degrees of tight control.4 New guidelines for glycemic control (HbA1c <7%) attempt to balance this body of evidence. The data and guidelines have been recently reviewed.5 Tight glycemic control may have a beneficial effect on a subset of skin-related, diabetes-associated disorders, but evidence is generally lacking.
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Diabetes is characterized by a state of relative or complete insulin deficiency, leading to gross defects in glucose, fat, and protein metabolism. In type 1 diabetes (formerly insulin-dependent DM), an insufficiency of insulin occurs through a gradual, immune mediated destruction of β islet cells in the pancreas, marked by autoantibodies. In type 2 diabetes (formerly noninsulin-dependent DM), chronic hyperglycemia occurs mainly through end-organ insulin resistance followed by a progressive decrease in pancreatic insulin release associated with aging. A fasting blood glucose level of ≥126 mg/dL or a random value of ≥200 mg/dL on two separate occasions confirms the diagnosis of diabetes. Diabetes may also now be diagnosed with an HbA1c level ≥6.5%. A genetic predisposition and a strong association with obesity exist in type 2 diabetes. In both types of diabetes, abnormalities of insulin and elevated blood glucose levels lead to metabolic, vascular, neuropathic, and immunologic abnormalities. Affected organs include the cardiovascular, renal, and nervous systems, the eyes, and the skin.
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Etiology and Pathogenesis
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Nearly all patients with diabetes have cutaneous findings related to their condition, including those listed in Box 151-1...