A benign skin disease which often reflects underlying medical conditions.
Most commonly associated with obesity and insulin resistance.
Some cases are associated with underlying malignancy and, where no other association is identified, malignancy is investigated by complete history and examination with relevant diagnostic tests.
Treatment of lesions is often not necessary unless they are extensive or cosmetically unacceptable and do not resolve with treatment of the underlying condition.
Acanthosis nigricans (AN) is a cutaneous disorder manifested by symmetric, hypertrophic, papillomatous, velvety, hyperpigmented plaques commonly found on flexural and intertriginous areas.It is associated with a wide array of medical conditions. AN may present at birth or in early childhood with a familial association, but is most commonly associated with obesity and an insulin-resistant state. Obesity-associated AN correlates with increasing body mass index, female sex, and Hispanic or black ethnicity. Malignancy-associated AN is rare and most often occurs with gastric adenocarcinoma, but may also be associated with other carcinomas and lymphomas.
History and exam
Key diagnostic factors
- black or Hispanic ancestry
- new pigmented velvety skin lesions in axillary or flexural areas
- lesions distributed on the posterior neck, axillae, vulva, umbilicus, inner thighs, and groin
- weight gain
- generalized distribution
- sudden appearance of multiple seborrheic keratoses
Other diagnostic factors
- age >40 years
- child/young adult
- female sex
- acrochordons (skin tags)
- acral distribution
- mucosal or palmoplantar lesions
- weight loss
- insulin resistance
- positive family history of AN or genetic syndrome
- family history of diabetes mellitus
Investigations to consider
- fasting blood glucose
- fasting blood insulin
- abdominal CT
- skin biopsy
initial presentation with underlying cause
unresolved despite treatment of underlying cause, or hereditary or idiopathic
- Epidermal nevus
- Dowling-Degos disease (reticular pigmented flexural anomaly)
- Confluent and reticulated papillomatosis (of Gougerot and Carteaud)
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