Management of Acanthosis Nigricans
The primary approach to treating acanthosis nigricans is addressing the underlying cause, particularly focusing on weight reduction for obesity-associated cases, with a target of 7-10% decrease in excess weight for patients with overweight/obesity.
Understanding Acanthosis Nigricans
Acanthosis nigricans (AN) is a cutaneous disorder characterized by symmetric, velvety, hyperpigmented plaques typically found in intertriginous areas such as the axilla, neck, inframammary regions, and groin 1. It serves as an important cutaneous marker of insulin resistance and can be associated with various systemic conditions.
Common Types of Acanthosis Nigricans:
- Obesity-associated (most common)
- Insulin resistance-related
- Syndromic
- Medication-induced
- Malignancy-associated (rare)
Diagnostic Approach
Clinical Assessment:
- Evaluate for typical presentation: symmetric velvety hyperpigmented plaques in intertriginous areas
- Common locations: neck, axilla, and knuckles; unusual locations may include the face 2
- Quantitative scales such as Burke scale can be used to describe severity 2
Laboratory Evaluation:
- Fasting insulin levels (normal <15 mU/L, borderline high 15-20 mU/L, high >20 mU/L) 3
- Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) using the formula: Fasting insulin (μU/mL) × Fasting glucose (mmol/L) / 22.5 (cutoff for insulin resistance ≥3.8) 3
- Fasting plasma glucose (impaired: 100-125 mg/dL) 3
- 2-hour Oral Glucose Tolerance Test (impaired: 140-199 mg/dL) 3
- HbA1C (prediabetes range: 5.7-6.4%) 3
- Fasting lipid panel 3
Management Algorithm
1. Address Underlying Cause:
Weight reduction: Most effective approach for obesity-associated AN
Discontinue causative medications if medication-induced 3
Treat underlying endocrinopathies 3
- For patients with diabetes: optimize glycemic control
- For PCOS: appropriate hormonal therapy
Evaluate for malignancy in cases with sudden onset, extensive involvement, or atypical presentation 5
2. Pharmacological Interventions:
Metformin: Key medication that improves both insulin resistance and acanthosis nigricans 3, 2
Topical treatments (for cosmetic improvement):
3. Procedural Interventions (for resistant cases):
- Chemical peels (trichloroacetic acid) 1
- Laser therapy options:
Special Considerations
For Children and Adolescents:
- Screening for prediabetes/type 2 diabetes should be considered after the onset of puberty or ≥10 years of age in children with:
- BMI ≥85th percentile AND
- One or more additional risk factors including acanthosis nigricans 4
- Testing should be repeated at minimum 3-year intervals, or more frequently if BMI is increasing 4
- Youth with acanthosis nigricans should be tested for pancreatic autoantibodies to exclude autoimmune type 1 diabetes 4
For Adults:
- Evaluate for metabolic syndrome components
- Consider more frequent monitoring for those with extensive AN
Prognosis and Expectations
It's important to counsel patients that while acanthosis nigricans is treatable, complete cure and disappearance of lesions are difficult to achieve 1. The condition typically improves with treatment of the underlying cause, particularly with weight reduction in obesity-associated cases.
Follow-up Recommendations
- Regular monitoring of metabolic parameters (glucose, insulin levels, lipids)
- Assessment of treatment response using standardized scales
- Continued emphasis on lifestyle modifications and weight management
Remember that early recognition and management of acanthosis nigricans can help identify and address underlying metabolic disorders, potentially preventing progression to more serious conditions such as type 2 diabetes.