A 48-year-old Indian man with a 10-year history of type 2 diabetes presents with velvety, hyperpigmented plaques over the neck and axillae. He is on metformin and glibenclamide. Recent investigations: fasting glucose 156 mg/dL, HbA1c 8.1%, fasting insulin 32 mIU/L. On skin examination, the plaques have exaggerated skin markings and are non-pruritic. There are no oral mucosal lesions. Abdominal imaging is unremarkable. Which of the following interventions is most likely to improve his acanthosis nigricans?

Explanation

## Management of Acanthosis Nigricans: Addressing the Root Cause **Key Point:** The only effective treatment for acanthosis nigricans is to **reduce insulin resistance and hyperinsulinemia**. Topical treatments and mechanical interventions do not address the underlying pathophysiology and provide only temporary cosmetic benefit. ### Why Thiazolidinediones Work **High-Yield:** Thiazolidinediones (pioglitazone, rosiglitazone) are the **gold standard** for treating acanthosis nigricans because they: 1. **Improve insulin sensitivity** at the tissue level (activate PPAR-γ receptors) 2. **Reduce fasting hyperinsulinemia** (often by 30–50%) 3. **Decrease IGF-1 receptor activation** on skin cells 4. Result in **regression of skin lesions** within 3–6 months of therapy ### Treatment Hierarchy | Intervention | Mechanism | Efficacy in AN | Evidence | |---|---|---|---| | **Thiazolidinediones** | ↓ Insulin resistance, ↓ hyperinsulinemia | **High** | Multiple RCTs show 50–80% improvement | | Weight loss + lifestyle | ↓ Insulin resistance | **Moderate** | Slow; requires 5–10% weight loss | | Topical retinoids | ↑ Keratinocyte turnover | **Low** | Cosmetic only; does not address cause | | Dermabrasion / laser | Mechanical removal | **Temporary** | Recurs as hyperinsulinemia persists | | Antifungals | None (not fungal) | **None** | Acanthosis nigricans is not infectious | **Clinical Pearl:** In this patient, switching from **glibenclamide** (a secretagogue that increases insulin output and may worsen hyperinsulinemia) to **pioglitazone** (which reduces insulin resistance) is the rational choice. The patient's fasting insulin of 32 mIU/L is significantly elevated, indicating ongoing severe insulin resistance despite glycemic control. ### Why This Patient Needs a Drug Switch - **Current regimen:** Metformin (insulin-sensitizing) + glibenclamide (insulin-stimulating) - **Problem:** Glibenclamide drives more insulin secretion, perpetuating hyperinsulinemia and acanthosis nigricans - **Solution:** Replace glibenclamide with pioglitazone to directly address insulin resistance **Mnemonic: "PPAR-γ agonists = Pioglitazone Promotes Adipocyte insulin Receptor sensitivity = Regression of Acanthosis nigricans"**