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Acanthosis nigricans

Last reviewed: 4 Sep 2023
Last updated: 19 Dec 2019



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
More key diagnostic factors

Other diagnostic factors

  • age >40 years
  • child/young adult
  • female sex
  • acrochordons (skin tags)
  • acral distribution
  • pruritus
  • mucosal or palmoplantar lesions
  • weight loss
Other diagnostic factors

Risk factors

  • obesity
  • insulin resistance
  • positive family history of AN or genetic syndrome
  • family history of diabetes mellitus
  • malignancy
  • medication
More risk factors

Diagnostic investigations

Investigations to consider

  • fasting blood glucose
  • fasting blood insulin
  • abdominal CT
  • skin biopsy
More investigations to consider

Treatment algorithm


initial presentation with underlying cause

unresolved despite treatment of underlying cause, or hereditary or idiopathic



David S. Cassarino, MD, PhD

Consultant Dermatopathologist

Southern California Permanente Medical Group

Sunset Medical Center

Los Angeles



DSC declares that he has no competing interests.


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



CK declares that she has no competing interests.

John English, MBBS, FRCP

Consultant Dermatologist

Department of Dermatology

Queen's Medical Centre

Nottingham University Hospitals




JE declares that he has no competing interests.

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