Approach
In most cases, treatment should be directed at the underlying cause, such as obesity, hyperinsulinemia, or malignancy.[2][36] Acanthosis nigricans (AN) usually regresses with treatment of the underlying disorder. Direct treatment of AN may be undertaken in patients without an identifiable association, or in those with hereditary causes. This is considered elective in most cases, as the lesions are not usually disfiguring, and there is no risk of malignant transformation of AN lesions. Many patients with minimal lesions will not desire treatment.[2]
Unresolved after treatment of underlying cause, or hereditary or idiopathic
Topical agents are the first-line direct treatment of AN, including ammonium lactate, vitamin D analogs, and retinoic acid.[36] Second-line agents are oral medications including isotretinoin, metformin, octreotide, and acitretin.[2][36][37] Most patients will respond to one or more of these medications.
Metformin should be avoided or used with caution in patients with renal impairment. It is contraindicated when eGFR is <30 mL/minute/1.73 m². Initiating treatment with metformin is not recommended in patients with an eGFR between 30 to 45 mL/minute/1.73 m²; however, in patients already on metformin with an eGFR that falls to <45 mL/minute/1.73 m², assess the risks and benefits of continuing treatment and discontinue metformin if their eGFR falls below 30 mL/minute/1.73 m². Metformin should also be discontinued in: patients undergoing imaging with iodinated contrast medium who have an eGFR between 30 to 60 mL/minute/1.73 m²; patients with a history of liver disease, heart failure, or alcoholism; or patients who are to be given intra-arterial iodinated contrast.
Laser therapy is an emergent approach in the treatment of AN, but appears to be effective.[38] It may be considered in patients with extensive, disfiguring or cosmetically unacceptable lesions that are unresponsive to topical or oral therapy. In darker skin types, there is a significant risk of post-treatment hypopigmentation. Types of laser treatment that have been reported include: long-pulsed (5 ms) Alexandrite laser: 10 sessions at 4- to 8-week intervals at 16 to 23 J/cm² with spot size of 10 or 12.5 mm and continuous-wave CO₂ laser: 3 sessions at 15 W at 4- to 6-week intervals.[39][40]
For patients with large, disfiguring lesions that are unresponsive to other treatments, surgical excision may be considered as a last resort. Lesions on the eyelid with functional impairment have also been effectively removed by surgery.[41]
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