Review Question - QID 221302

This patient with hyperpigmented skin in the setting of diabetes most likely has acanthosis nigricans secondary to insulin resistance. A commonly associated skin finding in patients with diabetes mellitus is acrochordons, which are soft, benign, often pedunculated skin tags.

Acanthosis nigricans manifests as brown-black velvety hyperpigmentation of the skin, typically arising in intertriginous areas of the body. It is caused by the activation of growth factor protein receptors, most commonly insulin-mediated activation of insulin-like growth factor receptors in keratinocytes in the setting of hyperinsulinemia or insulin resistance. In certain cases, it is a paraneoplastic sign of adenocarcinoma, typically of the gastrointestinal tract. Acanthosis nigricans is also associated with acrochordons, which are benign common skin neoplasms and also referred to as skin tags, fibroepithelial polyps, or papillomas. Treatment involves treatment of the underlying disease such as with weight loss, metformin, discontinuing offending drugs, and topical retinoids.

Novotny et al. review the epidemiology of obesity, type 2 diabetes, and acanthoma nigricans in Pacific Islanders. They discuss how environmental interventions, such as encouraging less consumption of sugar-sweetened beverages, decreased the prevalence of acanthosis nigricans. They recommend the continued study of these interventions among children in the Pacific region.

Figure/Illustration A is a clinical photograph demonstrating brown, velvety, hyperkeratotic plaques in the axilla (red circle). These findings are classically seen in patients with acanthosis nigricans.

Incorrect Answers:
Answer 1: Acne vulgaris is common in patients with polycystic ovary syndrome due to an elevation in testosterone. It is less associated with insulin resistance, which is the underlying pathology of acanthosis nigricans and acrochordons.

Answer 3: Dermatitis herpetiformis is a skin finding associated with celiac disease that manifests as pruritic papules, vesicles, and bullae most commonly located at the elbows, knees, and buttocks. Celiac disease is not associated with acanthosis nigricans.

Answer 4: Erythema nodosum manifests as painful, raised, and erythematous inflammatory lesions of the subcutaneous fat, most commonly on the anterior shins, and is associated with numerous conditions, such as inflammatory bowel disease, sarcoidosis, histoplasmosis, coccidioidomycosis, tuberculosis, streptococcal infections, and leprosy.

Answer 5: Xanthomas are a skin finding associated with hyperlipidemia, which can be associated with metabolic syndrome. They are the result of lipid accumulation in cells within the skin. Lesions typically appear as yellowish, waxy-appearing raised plaques.

Bullet Summary:
Acanthosis nigricans and acrochordons are usually associated with insulin resistance and obesity in younger patients.