Acanthosis nigricans (AN) has been reported in relation to insulin resistance (IR). We aim to review AN through an endocrine and metabolic perspective focusing on IR in association with metabolic complications such as obesity, diabetes mellitus (DM), and metabolic syndrome (MS) with/without polycystic ovary syndrome (PCOS). We revised English papers on PubMed covering publications from the last 5 years. The current prevalence of AN varies from 4.5 to 74% (or even 100%, depending on the studied population), with equal distribution among females and males. Despite higher incidence with an age-dependent pattern, an alarming escalation of cases has been noted for obesity and MS in younger populations. Most frequent IR-associated sites are the neck, axilla, and knuckles, but unusual locations such as the face have also been reported. Quantitative scales such as Burke have been used to describe the severity of the dermatosis, particularly in correlation with IR elements. Dermoscopic examination are required, for instance, in cases with sulcus cutis, hyperpigmented spots, crista cutis, and papillary projections. A skin biopsy may be necessary, but it is not the rule. Both IR that clinically manifests with or without obesity/MS correlates with AN; most studies are cross-sectional, with only a few longitudinal. The approach varied from screening during school periodic checkups/protocols/programs to subgroups of individuals who were already known to be at high cardio-metabolic risk. AN was associated with type2DM, as well as type 1DM. Females with PCOS may already display metabolic complications in 60-80% of cases, with AN belonging to the associated skin spectrum. AN management depends on underlying conditions, and specific dermatological therapy is not generally required, unless the patient achieves metabolic control, has severe skin lesions, or desires cosmetic improvement. In IR cases, lifestyle interventions can help, including weight control up to bariatric surgery. In addition, metformin is a key player in the field of oral medication against DM type 2, a drug whose indication is extended to PCOS and even to AN itself, outside the specific panel of glucose anomalies. In terms of cosmetic intervention, limited data have been published on melatonin, urea cream, topical retinoids, vitamin D analogs, or alexandrite laser. In conclusion, awareness of IR and its associated clinical features is essential to provide prompt recognition of underlying conditions. AN represents a useful non-invasive surrogate marker of this spectrum in both children and adults. The pivotal role of this dermatosis could massively improve endocrine and metabolic assessments.
Keywords: acanthosis nigricans; diabetes mellitus; endocrine; glucose; insulin resistance; metabolic syndrome; obesity; polycystic ovary syndrome.