Acanthosis nigricans

• Definition: a condition characterized by velvety, hyperpigmented plaques on the skin that most frequently involve intertriginous sites such as the axillae and neck
  • Acanthosis: velvety, thickening
  • nigricans: hyperpigmentation
• Etiology
  • Endocrinal
    • Diabetes mellitus type 2
    • PCOS
    • Cushing syndrome
  • Obesity: pseudoacanthosis nigricans
  • Familial causes: autosomal dominant inheritance
  • Drug-related causes (e.g., glucocorticoids, oral contraceptives)
• Pathogenesis: insulin, IGF, and/or other growth factors (e.g., fibroblast growth factor) → epidermal hyperplasia and fibroblast proliferation
• Clinical findings
  • Brown to black, intertriginous and/or nuchal hyperpigmentation that can develop into itching, papillomatous, poorly defined eruption
  • Symmetrical thickening of skin
  • Localization: axilla, groin, neck
• Differential diagnosis: malignant acanthosis nigricans

Tip

Don’t mess with skin pigmentation caused by Elevated ACTH