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

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)

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
Approach to AN in adult | Phiske M. M. (2014). An approach to acanthosis nigricans. Indian dermatology online journal, 5(3), 239–249. https://doi.org/10.4103/2229-5178.137765 Approach to AN in children | Phiske M. M. (2014). An approach to acanthosis nigricans. Indian dermatology online journal, 5(3), 239–249. https://doi.org/10.4103/2229-5178.137765