Acanthosis nigricans

Acanthosis nigricans is a dermatological condition of hyperkeratosis characterized by velvety, hyperpigmented plaques that are most frequently located in intertriginous areas such as the axillae or groin. It is often caused by an underlying metabolic or endocrine condition, e.g., diabetes or obesity. Acanthosis nigricans may also be genetic or associated with the use of certain medications (e.g., corticosteroids, oral contraceptives). Benign acanthosis nigricans must be distinguished from malignant acanthosis nigricans, which is the cutaneous manifestation of an underlying malignancy. Acanthosis nigricans is a clinical diagnosis, but testing is indicated to identify the underlying cause. Treatment is focused on the underlying cause and may include cosmetic treatment if requested by the patient.

• Benign acanthosis nigricans
  • Metabolic and endocrine conditions, e.g.: ^[1][2]
    • Diabetes
    • Obesity (sometimes referred to as pseudoacanthosis nigricans) ^[3]
    • Cushing syndrome
    • Polycystic ovarian syndrome
  • Drug-induced acanthosis nigricans (e.g., glucocorticoids, oral contraceptives, testosterone, protease inhibitors) ^[4]
  • Genetic factors
    • Familial acanthosis nigricans: autosomal dominant inheritance ^[3]
    • A manifestation of certain genetic syndromes ^[4]
• See also “Malignant acanthosis nigricans.” ^[1]

The stimulation of insulin, IGF, and/or other growth factor (e.g., fibroblast growth factor) receptors leads to epidermal hyperplasia, fibroblast proliferation, and hyperkeratosis. ^[1][2]

• Appearance ^[1][2]
  • Hyperpigmented, velvety, and scaly patches or plaques
  • Thickening of skin that can develop into papillomatous lesions
• Location ^[1][2]
  • Typically affects intertriginous areas (e.g., axillae, groin) and/or the back of the neck
  • Distribution is usually symmetrical.

• Identify and treat the underlying cause of acanthosis nigricans (e.g., discontinue offending medications, screen for diabetes, cancer screening if there is concern for malignant acanthosis nigricans). ^[1][5][6]
• Refer patients who request cosmetic treatment of skin lesions to dermatology; treatment options include: ^[5][6]
  • Topical agents (e.g., retinoids, keratolytics, calcipotriene)
  • Chemical peels
  • Oral retinoids (e.g., isotretinoin)
  • Laser therapy

Consider underlying malignancy in patients with a severe or atypical presentation (e.g., lesions with rapid onset of lesions, widespread distribution, and/or mucosal surface involvement). ^[1]

Acanthosis nigricans is a clinical diagnosis. Treatment of the underlying cause can resolve or improve the appearance of the skin lesions. ^[5][6]