Acanthosis Nigracans

Overview
  • Acanthosis Nigracans is an acquired development of localized skin thickening and hyperpigmentation especially of the neck and axillae, associated with certain systemic endocrine conditions such as diabetes mellitus and obesity.
Pathogenesis
  • The precise pathogenesis of acanthosis nigracans is unknown although derangements in growth factors is suspected. Whatever the case, the lesion appears to be secondary to systemic disorders, and is especially associated with insulin resistance. Consequently, acanthosis nigracans is frequently seen in patients with Type II Diabetes Mellitus and obesity, although it can occur secondary to certain drugs and internal malignancy, especially gastric carcinoma
Morphology
  • Patients with acanthosis nigracans develop velvety, dark plaques especially in the neck and axillae. Lesions develop insidiously in those with insulin resistance and may be noticed as areas of seemingly dirty skin that cannot be cleaned. An acute eruption of acanthosis nigracans is more worrisome for internal malignancy.
  • Histologically, lesions display acanthosis and hyperpigmentation of the epidermal basal layer without melanocytic hyperplasia.
Clinical Consequences
  • Acanthosis Nigracans is not dangerous in and of itself but is a marker of the systemic derangements already mentioned. Treatment of the underlying cause can lead to slow resolution or improvement of acanthosis nigracans.