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Q1: Diagnosis at the bedside (2 min)
Examiner: A patient with diabetes has yellow-brown shiny atrophic plaques with telangiectasia on the anterior shins. What is this?[1]
Candidate: Necrobiosis lipoidica. The diagnostic morphology is a pretibial yellow-brown waxy atrophic plaque with prominent telangiectasia and a red-brown or violaceous active rim. It is strongly associated with diabetes mellitus, but the plaque may persist despite good glycaemic control and can occur without diabetes.[1]
Examiner (push): What would you look for immediately?
Candidate: Ulceration, pain, infection, trauma, pulses, neuropathy and venous oedema. I would also ask about smoking and thyroid disease and check glycaemic status if diabetes is not already known.[1]
Q2: Histology and differentials (3 min)
Examiner: What does the biopsy show?[2]
Candidate: Palisading or layered horizontal granulomatous inflammation around necrobiotic collagen, often through much of the dermis, with histiocytes, giant cells, plasma cells and thickened blood vessels. There is relatively little mucin compared with granuloma annulare.[2]
Examiner (push): Distinguish it from granuloma annulare and pretibial myxoedema.[2]
Candidate: Granuloma annulare is usually a non-atrophic annular ring of papules on hands or feet, with focal mucin-rich palisading granulomas. Pretibial myxoedema is Graves-related thyroid dermopathy: indurated, waxy, non-pitting shin plaques or nodules with dermal mucin, often with ophthalmopathy or acropachy. NL is thin, atrophic, telangiectatic and ulcer-prone.[2]
Q3: Management (3 min)
Examiner: How do you manage active non-ulcerated NL?[3]
Candidate: I explain that it is chronic and difficult to clear. I advise smoking cessation, trauma avoidance, shin protection and diabetes risk management. I treat the active raised rim, not the atrophic centre, with a potent topical steroid such as clobetasol 0.05 percent once daily for 2 to 4 weeks or intralesional triamcinolone 5 to 10 mg/mL into the rim every 4 to 6 weeks. Tacrolimus 0.1 percent twice daily is a steroid-sparing option. I review response and avoid prolonged steroid use over the atrophic centre.[3]
Examiner (push): What if it is refractory?
Candidate: Specialist options include phototherapy, pentoxifylline 400 mg three times daily, antiplatelet therapy in selected patients, or biologic therapy such as TNF-alpha inhibition for severe refractory or ulcerative disease after TB, hepatitis and infection screening. The evidence base is limited, so escalation is individualised.[3]
Q4: Ulceration and safety net (3 min)
Examiner: One plaque ulcerates. What changes?[3]
Candidate: It becomes a chronic lower-limb wound as well as NL. I use non-adherent dressings, protect periwound atrophic skin, assess pulses, neuropathy and venous oedema, check ankle-brachial index if compression is planned, treat true cellulitis, and involve wound-care or vascular teams if healing is poor. I biopsy suspicious edges.[3]
Examiner (push): Suspicious for what?
Candidate: Rare squamous cell carcinoma arising in a chronic NL ulcer. A raised, rolled, indurated, bleeding, hyperkeratotic or enlarging edge must be biopsied rather than repeatedly dressed without diagnosis.[4]
Q5: Exam traps (2 min)
Examiner: Give me three traps.
Candidate: First, glycaemic control is essential for health but does not reliably clear NL. Second, do not inject or chronically apply potent steroid to the atrophic centre; treat the active rim. Third, do not call a Graves-related indurated non-pitting shin plaque NL — that is pretibial myxoedema until proven otherwise.[1][3]
References4ShowHide
- [1]Lima AL, Illing T, Schliemann S, et al. Cutaneous Manifestations of Diabetes Mellitus: A Review. American Journal of Clinical Dermatology, 2017.PMID 28374407
- [2]Terziroli Beretta-Piccoli B, Mainetti C, Peeters MA, et al. Cutaneous Granulomatosis: a Comprehensive Review. Clinical Reviews in Allergy & Immunology, 2018.PMID 29352388
- [3]Erfurt-Berge C, Renner R, Peckruhn M, et al. S1-Guideline for diagnosis and therapy of necrobiosis lipoidica. Journal der Deutschen Dermatologischen Gesellschaft, 2026.PMID 41420334
- [4]Vasari L, Simetić L, Kuna SK, et al. Cutaneous Squamous Cell Carcinoma Developing in Necrobiosis Lipoidica - A Case Report with Literature Review. Dermatology Practical & Conceptual, 2026.PMID 41912178