Acanthosis Nigricans: An Updated Review

BACKGROUND

Early recognition of acanthosis nigricans is important because acanthosis nigricans can be a cutaneous manifestation of a variety of systemic disorders and, rarely, as a sign of internal malignancy.

OBJECTIVE

The purpose of this article is to familiarize pediatricians with the clinical manifestations, evaluation, diagnosis, and management of acanthosis nigricans.

METHODS

A search was conducted in November 2021in PubMed Clinical Queries using the key term "acanthosis nigricans". The search strategy included all clinical trials, observational studies, and reviews published within the past 10 years. Only papers published in the English literature were included in this review. The information retrieved from the above search was used in the compilation of the present article.

RESULTS

Acanthosis nigricans is characterized by symmetric, hyperpigmented, and velvety plaques with ill-defined borders, typically involving intertriginous areas. Obesity is the most common cause of acanthosis nigricans which is increasingly observed in obese children and adolescents and can serve as a cutaneous marker of insulin resistance. Early recognition of acanthosis nigricans is important because acanthosis nigricans can also be a cutaneous manifestation of a variety of systemic disorders and, rarely, as a sign of internal malignancy. This may consist of weight reduction, discontinuation of causative drugs, treatment of underlying endocrinopathy, or treatment of an underlying malignancy. For patients with isolated acanthosis nigricans and for those whose underlying cause is not amenable to treatment, treatment of the lesion may be considered for cosmetic reasons. Topical retinoids, vitamin D analogs, chemical peels, and other keratolytics are often used for the treatment of localized lesions. Seldom, systemic therapy such as oral retinoids may be considered for extensive or generalized acanthosis nigricans and acanthosis nigricans unresponsive to topical therapy. Other uncommon treatment modalities include dermabrasion, laser therapy, and surgical removal.

CONCLUSION

Although acanthosis nigricans is treatable, a complete cure is difficult to achieve. The underlying cause should be treated, if possible, to resolve and prevent the recurrence of acanthosis nigricans. The diagnosis is mainly clinical, based on the characteristic appearance (symmetrically distributed, hyperpigmented, velvety, papillomatous, hyperkeratotic plaques with ill-defined borders) and the typical sites (intertriginous areas, flexural area, and skin folds) of the lesions. The diagnosis might be difficult for lesions that have atypical morphology or are in an unusual location. Clinicians should be familiar with the clinical signs, evaluation, diagnosis, and therapy of acanthosis nigricans because of the link between it and underlying diseases.

Drug-induced acanthosis nigricans: A systematic review and new classification

Drug-induced acanthosis nigricans is an uncommon subtype of acanthosis nigricans and the data on this topic is not well understood by clinicians as it is presently limited in the literature. Previous reports of drug-induced acanthosis nigricans have simply consisted of a list of drugs possibly implicated in causing acanthosis nigricans. Several drugs listed are based on single case reports without biopsy confirmation, report of clearing on stopping the drug or reporting on whether acanthosis nigricans recurred with drug rechallenge. A comprehensive literature search was conducted using PubMed, EMBASE(Ovid), Cochrane Library, Scopus, and Web of Science electronic databases. The authors screened the initial result of the search strategy by title and abstract using the following inclusion criteria: eligible studies included those with patients who developed acanthosis nigricans secondary to a drug. This study is the first to comprehensively review the drugs that have been implicated in the development of acanthosis nigricans. A total of 38 studies were included in the systematic review, and a total of 13 acanthosis nigricans inducing drugs were identified. Nicotinic acid and insulin were the two most significant drugs that were reported to cause acanthosis nigricans. By using the results of this study, we created a revised classification system of drug-induced acanthosis nigricans which can be used as a concise framework for clinicians to refer to.

Introduction of a novel quantitative scoring system for acanthosis nigricans and its validation in a pilot study

Inconsistent data exist regarding the diagnostic value of acanthosis nigricans (AN) or skin tags as clinical markers for obesity or diabetes. In an outpatient department-based prospective study, we designed a scoring for AN severity (SCANS) to evaluate AN and skin tags, their correlation with obesity or diabetes. Quantification of AN in six anatomic sites, in consideration of the affected skin surface areas, texture changes, number of skin tags, leads to a total severity score between 0 and 46. Among 336 adult patients (aged ≥18 years) with AN, a higher BMI was associated with AN (r = 0.299, P < .001), but not with diabetes (P = .43), as compared with 243 age- and sex-matched controls without AN. Among nondiabetics, AN scores were significantly correlated with waist circumference (r = 0.131, P = .024) and total cholesterol levels (r = 0.155, P = .04). Skin tags alone in the absence of AN were not associated with obesity (P = .333) or diabetes (P = .164). The total AN scores were positively correlated with the presence of skin tags (r = 0.132, P < .001), and the involvement of anterior neck (r = 0.668, P < .001) and axilla (r = 0.793, P < .001). Knuckles and groins were unaffected in our series. Our results indicate that combination of AN with skin tags can be used as clinical marker for obesity, but not for diabetes. Large-scale studies on patients of different ethnic background are required to further validate our proposed scoring.

Acanthosis nigricans: A fold (intertriginous) dermatosis

Acanthosis nigricans (AN) is a mucocutaneous disorder that is characterized by focal or diffuse hyperkeratotic, surfaces, which are symmetrically distributed hyperpigmented lesions of the skin. It rarely affects mucosal surfaces like oral cavities. Although it is commonly seen in adolescents, AN is also increasingly seen in children who are obese. Recent studies have found that AN can be a cutaneous indicator of insulin resistance and malignancy. Acanthosis nigricans has been associated with type 2 diabetes mellitus, obesity, endocrinopathies, drugs, and malignancies.