Acanthosis nigricans (AN)

Introduction

Common cutaneous condition characterized by thick velvety hyperpigmented plaques of the intertriginous, flexural, and less commonly extensor areas of the skin.

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Aetiology

Associated conditions:

• Disorders associated with insulin resistance (M/C)
  • Obesity-associated AN (M/C type)
  • Type 2 diabetes
  • PCOS
• Internal malignancy
• Endocrine disorders
• Drug reactions

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Pathophysiology

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Clinical features

• Asymptomatic area of darkening and thickening of the skin, pruritus, and lesions that are velvety, hyperpigmented macules and patches and progress to palpable plaques.
• Typically occur in areas of skin folds like the groin, axillae, or posterior neck (M/C)

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Management

Topical retinoids

First-line treatment

• Tretinoin 0.1% cream/gel
• Triple therapy: Tretinoin 0.05% + hydroxyquinone 4% + fluocinolone acetonide 0.01%
• Adapalene gel

Topical vitamin D analogs

Inhibit keratinocyte proliferation and promote differentiation by increasing keratinocyte intracellular calcium and cyclic GMP levels

• Calcipotriene

Superficial chemical peels

Relatively safe and effective treatment option for AN

• Trichloroacetic acid (TCA): Chemical exfoliating agent that causes destruction of the epidermis with subsequent repair and rejuvenation

Oral retinoids (isotretinoin and acitretin)

Normalization of epithelial growth and differentiation

Metformin and rosiglitazone

Treatment of AN associated with insulin resistance

• Metformin increases peripheral insulin responsiveness, resulting in reduction of glucose production, hyperinsulinemia, body weight, and fat mass, as well as an increase in insulin sensitivity in patients with insulin resistance and AN

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