SynopsisCodesLook ForDiagnostic PearlsDifferential Diagnosis & PitfallsBest TestsManagement PearlsTherapyDrug Reaction DataReferences

Information for Patients

View all Images (95)

Acanthosis nigricans in Adult
See also in: Anogenital
Other Resources UpToDate PubMed

Acanthosis nigricans in Adult

See also in: Anogenital
Contributors: Kyle Cheng MD, Belinda Tan MD, PhD, Oyetewa Oyerinde MD, Callyn Iwuala BA, Susan Burgin MD
Other Resources UpToDate PubMed


Acanthosis nigricans (AN) is a localized skin disorder manifesting with hyperpigmented, velvety plaques typically located in flexural and intertriginous regions. The precise pathogenesis is unknown but is speculated to involve the stimulation of insulin-like growth factor receptors and tyrosine kinase receptors on keratinocytes and fibroblasts. In the United States, Americans of African descent are 25 times more likely to have acanthosis nigricans than Americans of European descent. The condition is reported to be most common in Native Americans.

AN can be classified into 8 types:

I. Obesity-associated – Most common; linked to diabetes, insulin resistance, high body mass index (BMI), metabolic syndrome, and polycystic ovarian syndrome (PCOS).

II. Malignancy-associated / cutaneous paraneoplastic syndrome – Most commonly associated with gastric carcinoma, but numerous other malignancies have been reported. Elderly nonobese patients with new AN should have malignancy considered as a cause. Atypical (palmar, perioral, or mucosal) distributions or acute-onset AN may be more associated with malignancy.

III. Drug-induced – Niacin (nicotinic acid) is the most closely associated medication, but AN can also be caused by oral contraceptives, corticosteroids, diethylstilbestrol, heroin, fusidic acid, methyltestosterone, protease inhibitors, and folate.

IV. Syndromic – Type A refers to patients with HAIR-AN (hyperandrogenism, insulin resistance, and acanthosis nigricans) syndrome and acromegaly. Type B is typically seen in women who have uncontrolled diabetes mellitus and autoimmune diseases (systemic lupus erythematosus, scleroderma, Sjögren syndrome, and Hashimoto thyroiditis). This type is associated with the formation of antibodies against insulin receptors.

V. Acral – Affects elbows, knees, and knuckles. Typically seen in healthy sub-Saharan Africans.

VI. Unilateral – Also called nevoid. Usually represents an epidermal nevus in childhood.

VII. Benign – Rare autosomal dominant type developing at birth or during childhood.

VIII. Mixed – Any 2 or more of the above types combined.

Other related endocrinopathies include pituitary hypogonadism, thyroid disease, Addison disease, and acromegaly.


L83 – Acanthosis nigricans

402599005 – Acanthosis nigricans

Look For

Subscription Required

Diagnostic Pearls

Subscription Required

Differential Diagnosis & Pitfalls

  • Confluent and reticulated papillomatosis (CARP) presents with reticulated, pigmented patches on the trunk.
  • Keratinocytic epidermal nevus and Becker nevus are usually not symmetric and often have associated hypertrichosis.
  • Hemochromatosis and Addison disease have skin darkening without epidermal thickening.
  • Localized plaques of Bullous congenital ichthyosiform erythroderma have more corrugated surfaces.
  • Pellagra presents with photodistributed dermatitis (Casal's necklace) as well as diarrhea and dementia (the 3 Ds).
  • Large plaque parapsoriasis tends to have diffusely distributed, scaly plaques.
  • Pemphigus vegetans has verrucous ulcerated plaques.
  • Ashy dermatosis (ashy dermatosis) usually has diffuse hyperpigmentation over the trunk.
  • Terra firma-forme dermatosis can be removed by rubbing with isopropyl alcohol.
  • Granular parakeratosis
  • Reticulate pigmented anomaly of flexures

Best Tests

Subscription Required

Management Pearls

Subscription Required


Subscription Required

Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

Subscription Required


Subscription Required

Last Updated:10/25/2016
Copyright © 2024 VisualDx®. All rights reserved.
Patient Information for Acanthosis nigricans in Adult
Print E-Mail Images (95)
Contributors: Medical staff writer
Premium Feature
VisualDx Patient Handouts
Available in the Elite package
  • Improve treatment compliance
  • Reduce after-hours questions
  • Increase patient engagement and satisfaction
  • Written in clear, easy-to-understand language. No confusing jargon.
  • Available in English and Spanish
  • Print out or email directly to your patient
Copyright © 2024 VisualDx®. All rights reserved.
Acanthosis nigricans in Adult
See also in: Anogenital
A medical illustration showing key findings of Acanthosis nigricans : Axilla, Hyperpigmented patch, Neck
Clinical image of Acanthosis nigricans - imageId=40959. Click to open in gallery.  caption: 'Acanthotic, thickened, ridged, and hyperpigmented plaques on the posterior neck.'
Acanthotic, thickened, ridged, and hyperpigmented plaques on the posterior neck.
Copyright © 2024 VisualDx®. All rights reserved.