Summary
Definition
Acanthosis nigricans (AN) is a cutaneous disorder manifested by symmetric, hypertrophic, papillomatous, velvety, hyperpigmented plaques commonly found on flexural and intertriginous areas.[1] 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.[2][3][4][5][6][7] Obesity-associated AN correlates with increasing body mass index, female sex, and Hispanic or black ethnicity.[5] Malignancy-associated AN is rare and most often occurs with gastric adenocarcinoma, but may also be secondary to other carcinomas and lymphomas.[8][9][10][Figure caption and citation for the preceding image starts]: Acanthosis nigricans involving the axilla of an obese Caucasian womanFrom the collection of Melvin Chiu, MD [Citation ends].
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
- pruritus
- mucosal or palmoplantar lesions
- weight loss
Risk factors
- obesity
- insulin resistance
- positive family history of AN or genetic syndrome
- family history of diabetes mellitus
- malignancy
- medication
Diagnostic tests
Tests to consider
- fasting blood glucose
- fasting blood insulin
- abdominal CT
- skin biopsy
Treatment algorithm
initial presentation with underlying cause
unresolved despite treatment of underlying cause, or hereditary or idiopathic
Contributors
Authors
David S. Cassarino, MD, PhD
Consultant Dermatopathologist
Southern California Permanente Medical Group
Sunset Medical Center
Los Angeles
CA
Disclosures
DSC declares that he has no competing interests.
Acknowledgements
Dr David Cassarino would like to gratefully acknowledge Dr Laura Westerling for her contribution to this topic. LNW declares that she has no competing interests.
Peer reviewers
Christine Ko, MD
Assistant Professor of Dermatology
Department of Dermatology
Yale University
New Haven
CT
Disclosures
CK declares that she has no competing interests.
John English, MBBS, FRCP
Consultant Dermatologist
Department of Dermatology
Queen's Medical Centre
Nottingham University Hospitals
Nottingham
UK
Disclosures
JE declares that he has no competing interests.
Differentials
- Epidermal nevus
- Dowling-Degos disease (reticular pigmented flexural anomaly)
- Confluent and reticulated papillomatosis (of Gougerot and Carteaud)
More Differentials
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