Acanthosis Nigricans: Causes, Significance & Clinical Implications

Acanthosis Nigricans: Clinical Sign of Metabolic Dysfunction

Acanthosis nigricans presents as velvety, hyperpigmented, thickened skin in body folds (axillae, neck, groin, inframammary). It is a cutaneous marker of underlying systemic conditions.

Primary Associations

• Insulin Resistance / Hyperinsulinemia (most common)
• Type 2 Diabetes / Prediabetes
• Obesity (especially central adiposity)
• Polycystic Ovary Syndrome (PCOS)
• Metabolic Syndrome
• Endocrine disorders: Cushing's, acromegaly, hypothyroidism
• Medications: Oral contraceptives, corticosteroids, niacin, growth hormone
• Malignancy (rare): Gastric adenocarcinoma (paraneoplastic — malignant acanthosis nigricans)
• Genetic forms: Benign familial, syndromic

Clinical Significance

• Screening opportunity: Visible sign prompting metabolic workup
• Pediatric concern: Rising with childhood obesity — early insulin resistance marker
• Not just cosmetic: Indicates systemic metabolic stress

Evaluation When Identified

• Fasting glucose, HbA1c, insulin
• Lipid panel
• Thyroid function
• Consider testosterone, DHEAS (PCOS)
• If malignant suspected: age-appropriate cancer screening

Management

• Treat underlying condition (weight loss, glycemic control)
• Topical retinoids, vitamin D analogs, laser (cosmetic improvement only)
• Discontinue offending medications if possible

Acanthosis nigricans is a clinical clue, not a diagnosis itself—always investigate the underlying etiology.