Acanthosis nigricans and the metabolic syndrome

Abstract

Acanthosis nigricans (AN) describes clinically a darkly pigmented thickening skin, which produces epidermal and dermal hyperplasia with orthokeratotic hyperkeratosis and papillomatosis of the stratum spinosum with basal layer hyperpigmentation, in the absence of actual acanthosis and melanocytosis on histologic examination. It is a reactive cutaneous change closely associated with obesity, insulin resistance, and hyperinsulinemia; endocrinopathy; or malignancy, in particular gastrointestinal adenocarcinoma. The prevalence varies, and ethnicity seems an independent factor. Evidence indicates that AN is a useful clinical marker to identify patients susceptible to insulin resistance, the MetS, and type 2 diabetes. Whether AN can be regarded as one of the risk factors for the diagnosis of MetS, like large waist circumference and elevated blood pressure, is unclear. Correlation between AN and degree of hyperglycemia, insulin resistance, impaired glucose tolerance, and dyslipidemia remains to be confirmed. Classification of AN is inconsistent, and assessment of its severity is less studied. Several monogenic diseases are known to present extensive AN of early onset and can act as models for a better understanding of its pathogenesis. Therapeutic options are limited, and results are unsatisfactory. Retinoids seem to be the most effective topical treatment, and insulin sensitizers, represented by metformin to target insulin resistance, are promising, but controlled studies are lacking. Change of lifestyle to diminish the manifestations of MetS is beneficial, but the influence remains unclarified. Spontaneous remission seems more complete in paraneoplastic AN than in the form associated with obesity and insulin resistance. (C) 2018 Elsevier Inc. All rights reserved.