Acanthosis nigricans
Acanthosis nigricans is a symmetric, velvety, hyperpigmented thickening of intertriginous skin that is most often a cutaneous marker of insulin resistance, and occasionally a paraneoplastic sign of visceral adenocarcinoma. Management is directed at the underlying driver, primarily glycemic control and weight loss, rather than the plaques themselves.
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What this article covers
- Overview
A cutaneous marker, not a primary skin disease: acanthosis nigricans is a reaction pattern of the skin, velvety, hyperpigmented, thickened plaques in body folds, that signals an underlying metabolic…
- Epidemiology
Tracks with obesity prevalence: acanthosis nigricans is a common finding in patients with obesity and is frequently noted on examination in this population.
- Risk factors
Obesity: the single most common association, with acanthosis nigricans appearing as a marker of insulin resistance in this setting.
- Pathophysiology
Hyperinsulinemia drives epidermal proliferation: in insulin-resistant states, compensatory hyperinsulinism is thought to stimulate keratinocyte and dermal fibroblast proliferation through…
- Clinical features
Velvety, hyperpigmented, thickened plaques on the neck and intertriginous folds (axillae, groin) are the defining feature; the texture, not just the color, is diagnostic.
- Differential diagnosis
Confluent and reticulated papillomatosis: erythematous to dark brown, net-like reticulated patches of the trunk, neck, and axillae in young adults, unlike the confluent velvety plaque of acanthosis…
- Diagnosis
First, establish this as a clinical diagnosis on inspection: the physical examination, velvety, hyperpigmented, symmetric plaques in the neck and flexures, is usually sufficient, and biopsy is rarely required.
- Management
First, treat the underlying driver rather than the skin lesion itself: acanthosis nigricans is typically not treated directly.
- Complications
Missed or delayed diagnosis of an underlying malignancy is the most serious complication when atypical features are not recognized and investigated.
- Prognosis
Generally reversible with correction of the underlying driver: plaques improve as obesity, insulin resistance, or the associated endocrinopathy is treated.
- Prevention
Weight management to prevent or reduce obesity-driven insulin resistance is the primary preventive measure for the common metabolic form.
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