What workup, if any, is required to classify acanthosis nigricans (AN) in a known diabetic? Is there a treatment?
—Cconnie Walker, PA-C, Port Angeles, Wash.

AN can occur in several settings: benign, obesity-associated, cancer-associated, acral, unilateral, medication-induced, and mixed (in which two types are evident). AN-associated diabetes mellitus may be unrelated to other concurrent conditions, noninsulin-dependent, and secondary to hyperinsulinemia, or it may be an associated feature of an AN-related syndrome (such as Lawrence-Seip syndrome, Rabson-Mendenhall syndrome, or polycystic ovary syndrome) (Cutis. 1995;55:337-341). Fasting plasma levels of glucose and insulin (performed at the same time) can be obtained to screen for AN-associated insulin resistance. In patients with obesity-associated AN, weight loss may be helpful; in addition, AN may be improved by using a topical regimen of 12% ammonium lactate lotion or cream twice daily and 0.05% tretinoin cream once at night (Cutis. 2003;71:33-34).
—Philip R. Cohen, MD (105-14)

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