Derm Cases · Dermatology / Endocrinology / Oncology red flags
OSCE — velvety neck darkening: insulin resistance vs paraneoplastic AN
An 8-minute OSCE station on acanthosis nigricans morphology, insulin-resistance work-up, drug and syndrome causes, and urgent screening when rapid extensive AN suggests malignancy.
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Study tools
Target exams
NEET-PGINICETUSMLEPLABMRCP
Prompt
An 8-minute OSCE station on acanthosis nigricans morphology, insulin-resistance work-up, drug and syndrome causes, and urgent screening when rapid extensive AN suggests malignancy.
Brief (to candidate)
A 42-year-old with BMI 34 has progressive velvety hyperpigmented thickening of the neck and axillae. A second vignette is a non-obese 58-year-old with rapidly progressive extensive AN and tripe palms. You have 8 minutes to explain pathogenesis, work up metabolic AN, and escalate the paraneoplastic red flag.
[8]Candidate instructions
- Describe classic AN morphology and sites.
- Link common AN to insulin resistance and plan metabolic assessment.
- List non-metabolic causes (drugs, syndromes).
- Recognise malignant AN red flags and next investigations.
- Outline management priorities (treat cause; topical options secondary).
Examiner checklist (mark each domain / 10)
| Domain | Key actions expected |
|---|---|
| Morphology | Soft velvety, hyperpigmented, papillomatous plaques in flexures (neck, axillae, groin, umbilicus); may involve knuckles/face in severe disease[1][2] |
| Pathogenesis | Hyperinsulinaemia activates IGF-1 receptor pathways on keratinocytes/fibroblasts → proliferation/papillomatosis; not primary melanocytic disease alone[1][4] |
| Metabolic work-up | Screen obesity/T2DM/metabolic syndrome/PCOS: fasting glucose/HbA1c, lipids, BP; lifestyle and glycaemic control first-line for skin improvement context[4][6] |
| Other causes | Drugs (nicotinic acid, systemic steroids, OCP, GH, some PIs); genetic insulin-resistance syndromes; endocrine disease; rare malignancy-associated AN |
| Malignant red flags | Rapid, extensive AN in non-obese adult; tripe palms; Leser-Trélat seborrhoeic keratoses → urgent GI work-up (gastric adenocarcinoma classic association)[1][2] |
| Skin therapy | Treat driver disease; topical retinoids/keratolytics and emollients adjunctive; counsel pigmentation may lag metabolic control |
| Communication | Avoid cosmetic-only framing when systemic disease likely; safety-net weight loss, polyuria, progressive palms/mucosa |
Model key actions
- Diagnose obesity-associated AN of insulin resistance and order metabolic screen.[4][6]
- Escalate rapid extensive AN + tripe palms for malignancy screen, especially gastric.[1]
- Explain mechanism and that bleaching alone does not treat the driver.
Common errors
- Calling AN "dirt" or pure fungal intertrigo without metabolic thought.
- Missing paraneoplastic pattern in lean rapid-onset disease.
- Treating only with skin lighteners while ignoring glucose/HbA1c.
- Confusing AN with melasma (distribution and texture differ).
References6ShowHide
- [1]Das A, Datta D, Kassir M, et al. Acanthosis nigricans: A review. Journal of cosmetic dermatology, 2020.PMID 32516476
- [2]Leung AKC, Lam JM, Barankin B, et al. Acanthosis Nigricans: An Updated Review. Current pediatric reviews, 2022.PMID 36698243
- [4]Lause M, Kamboj A, Fernandez Faith E. Dermatologic manifestations of endocrine disorders. Translational pediatrics, 2017.PMID 29184811
- [6]Abate MCMO, Aroucha PMT, Nóbrega DVMD, et al. Cutaneous manifestations of diabetes mellitus: a narrative review. Einstein (Sao Paulo, Brazil), 2025.PMID 40105573
- [7]Hermanns-Lê T, Scheen A, Piérard GE. Acanthosis nigricans associated with insulin resistance : pathophysiology and management Am J Clin Dermatol, 2004.PMID 15186199
- [8]Lam CPM, Chan MWM. Metastatic adenocarcinoma of the stomach presenting as malignant acanthosis nigricans and tripe palms: a case report Hong Kong Med J, 2023.PMID 37489275