Updated: 7/16/2018

Acanthosis Nigricans

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Snapshot
  • A 56-year-old man presents with several giant dark spots that appear "dirty." He describes them as velvet-like. Scrubbing the lesions with soap and water does not remove the skin abnormality. On exam, there are hyperpigmented plaques in the axillary and neck fold region. His primary care doctor is concerned for an occult malignancy given its rapid developement.
Introduction
  • Velvety hyperpigmentation of flexural skin
  • Pathogenesis
    • hyperplasia of stratum spinosum of epidermis
    • cutaneous marker of high insulin
  • Associated conditions
    • obesity
    • diabetes
    • other states of hyperinsulinemia (e.g., Cushing’s disease)
    • medications
    • occult malignancy
      • gastric cancer
      • MEN 2B
Presentation
  • Symptoms
    • non-tender, non-itchy dirty appearance that is not removed with washing
    • with diabetes and obesity
      • gradual onset
    • with malignancy
      • rapid and sudden onset
  • Physical exam
    • velvet-textured, hyperpigmented plaques
    • surface is rough, warty, or papillomatous
    • locations
      • axillae
      • neck
      • other skin folds less common
Evaluation
  • Laboratory values
    • elevated glucose
    • elevated insulin
  • Screen for diabetes or malignancy if appropriate
Differential Diagnosis
  • Melasma
  • Fungal infection
  • Atopic dermatitis
Treatment
  • Treat underlying condition
  • Lesions do not typically require treatment
    • optional: topical retinoids
Prognosis, Prevention, and Complications
  • Prognosis
    • for obesity-related
      • plaques improve with weight loss
    • for malignancy-related
      • plaques resolve with successful treatment
 

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