From the Guidelines
The workup for acanthosis nigricans should prioritize identifying underlying causes of insulin resistance, obesity, and potential malignancies, as suggested by the presence of acanthosis nigricans, which may be associated with insulinoma or malignancy, particularly adenocarcinoma of the stomach 1. When evaluating a patient with acanthosis nigricans, it is crucial to consider the following key factors:
- A thorough history and physical examination to identify signs of insulin resistance, such as obesity, and to assess for the presence of other endocrinopathies
- Laboratory testing, including fasting blood glucose, hemoglobin A1c, fasting insulin levels, and lipid panel, to evaluate for metabolic syndrome and diabetes
- Thyroid function tests (TSH, free T4) to rule out thyroid disorders
- In patients with rapid-onset acanthosis nigricans, especially if not associated with obesity or family history, consider age-appropriate cancer screening, including complete blood count, comprehensive metabolic panel, and specific cancer markers based on symptoms, as malignancy is a potential underlying cause 1
- For patients with suspected polycystic ovary syndrome, obtain testosterone levels, DHEAS, and consider pelvic ultrasound Management of acanthosis nigricans focuses primarily on treating the underlying condition, with recommendations including:
- Weight loss, exercise, and dietary modifications for obesity-related cases
- Medications such as topical retinoids (tretinoin 0.05-0.1% cream applied nightly), alpha hydroxy acids, or salicylic acid preparations to improve the appearance of the skin
- Oral metformin (500-2000 mg daily in divided doses) may be beneficial in cases associated with insulin resistance, as it can help improve insulin sensitivity and reduce the risk of developing type 2 diabetes 1
From the Research
Diagnosis of Acanthosis Nigricans
- The diagnosis of Acanthosis Nigricans is mainly clinical, based on the characteristic appearance and typical sites of the lesions 2, 3
- Histopathology may be needed for confirmation, characterized by papillomatosis and hyperkeratosis of the skin 2
- Other investigations may include fasting lipoprotein profile, fasting glucose, fasting insulin, hemoglobin, and alanine aminotransferase for obesity-associated AN 2
- Radiological investigations such as plain radiography, ultrasonography, magnetic resonance imaging/computerized tomography may be needed for malignancy-associated AN 2
Classification of Acanthosis Nigricans
- Different varieties of Acanthosis Nigricans include benign, obesity-associated, syndromic, malignant, acral, unilateral, medication-induced, and mixed AN 2, 4
- Obesity is the most common cause of Acanthosis Nigricans, which can serve as a cutaneous marker of insulin resistance 3
Treatment of Acanthosis Nigricans
- Treatment involves general measures such as weight reduction and addressing the underlying cause, if any 4, 3
- Topical drugs such as retinoids, vitamin D analogs, and keratolytics may be used for the treatment of localized lesions 4, 3, 5
- Oral drugs such as retinoids and insulin sensitizers may be considered for extensive or generalized Acanthosis Nigricans and Acanthosis Nigricans unresponsive to topical therapy 4, 3
- Other treatment options include chemical peels, lasers, dermabrasion, and surgical removal 4, 3, 5, 6