What is the treatment for dark skin pigmentation in the neck and axilla, possibly acanthosis nigricans?

Treatment of Acanthosis Nigricans in the Neck and Axilla

For dark skin pigmentation in the neck and axilla consistent with acanthosis nigricans, address the underlying cause first (weight reduction if obesity-related, discontinue causative medications, or treat endocrinopathy), then use topical retinoids as first-line therapy for the hyperpigmented plaques themselves. 1, 2

Identify and Address the Underlying Cause

The most critical step is determining what's driving the acanthosis nigricans, as treating the root cause is essential for resolution and preventing recurrence:

• Obesity-associated AN (most common): Weight reduction is the most scientific and practical management strategy 2. Check fasting glucose, fasting insulin, HOMA-IR (homeostasis model assessment-insulin resistance), fasting lipoprotein profile, hemoglobin, and alanine aminotransferase 1

• Medication-induced AN: Review current medications and discontinue causative drugs if possible 3

• Endocrinopathy-related AN: Evaluate for insulin resistance, metabolic syndrome, type 2 diabetes, and other endocrine disorders; treat the underlying condition 1, 3

• Malignancy-associated AN (rare but critical): If rapid onset, extensive distribution, or patient appears systemically unwell, consider radiological investigations (plain radiography, ultrasonography, MRI/CT) to rule out internal malignancy 1

Topical Treatment for the Lesions Themselves

First-line topical therapy:

• Topical retinoids are the primary treatment for hyperpigmented plaques 1, 2, 4, 3
  • Use 0.1% retinoic acid (tretinoin) cream applied to affected areas 5
  • The main limiting factor is skin irritation, which can be managed with combination approaches 4

Alternative or adjunctive topical agents:

• Vitamin D analogs can be used as an alternative or in combination with retinoids 2, 3

• Keratolytics help address the hyperkeratosis component 2, 3

• Avoid hydroquinone for this indication - while it's a skin bleaching agent, it requires careful monitoring for adverse effects including atrophy, pigmentary changes, and has carcinogenic concerns in animal studies 6. The evidence does not support its use specifically for acanthosis nigricans.

Combination Approaches

When retinoid irritation limits therapy, combinational approaches have proven beneficial 4:

• Retinoids combined with vitamin D analogs reduce irritation while maintaining efficacy 4
• Retinoids combined with keratolytics can enhance hyperkeratosis reduction 2

Systemic and Procedural Options

For extensive or refractory cases:

• Oral retinoids may be considered for extensive or generalized AN unresponsive to topical therapy 1, 3

• Metformin (insulin sensitizer) is commonly used, particularly in obesity-associated AN with insulin resistance 1, 2

• Chemical peels with trichloroacetic acid can be effective 2

• Laser therapy options include long-pulsed alexandrite, fractional 1550-nm erbium fiber, and CO2 lasers 2

Critical Caveats

• Complete cure is difficult to achieve - even with treatment, total disappearance of lesions is uncommon 2, 3

• Recurrence is likely unless the underlying cause is adequately addressed 3

• Rotation of insulin injection sites is essential if the patient has diabetes and injects insulin in affected areas, as repetitive high-dose insulin administration can worsen or cause AN 5

• Monitor for systemic associations - AN in the neck and axilla can be a cutaneous marker of insulin resistance, metabolic syndrome, or rarely internal malignancy 3