Necrobiosis lipoidica

Meet the patient

A 38-year-old woman with type 1 diabetes has noticed, over a year, two shiny yellow-brown patches on her shins — thin-skinned, threaded with visible vessels, ringed by a dull red edge. Last week she knocked one against a coffee table and it broke down into a slow, painful ulcer. She assumes her sugars are to blame; they are not, quite.^[1][8]

Two questions frame every NL plaque: is it the classic three-layered shin plaque? — because that morphology is near-pathognomonic — and what is the active part? The centre is burnt-out atrophy; the rim is where the inflammation — and therefore the treatment — lives. Confuse the two and you worsen the disease.^[1][3]

Read the plaque in three layers — the morphology sentence

"A yellow-brown, waxy, shiny, atrophic plaque with prominent telangiectasia and a violaceous raised rim on the pretibial shin" is necrobiosis lipoidica until proven otherwise. Say that sentence in a viva and the diagnosis marks are banked.^[1]

The three layers are the teaching device. The centre is yellow-brown, waxy, shiny and depressed because the dermis has wasted. The surface is telangiectatic because the thinned skin reveals the vessels beneath. The edge is red-brown or violaceous and slightly raised because that is where the granulomatous inflammation is actively advancing. Lesions are usually on the anterior shins, bilateral but not mirror-symmetrical, though arms, scalp, face and trunk can be involved.^[1][8]

Etymology for viva gold: necrobiosis means degeneration of connective tissue — not infection, not true necrosis — and lipoidica reflects the lipid-rich yellow of the mature plaque. The old name necrobiosis lipoidica diabeticorum is still examined, but it is too narrow: NL occurs without diabetes too, so the modern term drops the suffix.^[1][2]

The diabetes link — and the trap that control does not clear it

NL is strongly associated with diabetes mellitus — type 1 in younger patients, type 2 in older ones — and it can precede, follow or coincide with the diabetes. But here is the examiner trap, stated plainly: tight glycaemic control does not reliably improve established NL, and NL appears in people without diabetes. So diabetes optimisation is a comorbidity intervention (essential for overall health and wound healing), not a reliable skin cure.^[1][3]

The safest phrasing for a viva: NL is strongly associated with diabetes, but most people with diabetes never develop NL, and not every person with NL has diabetes. Autoimmune thyroid disease is the other recognised comorbidity, and smoking compounds the microvascular injury that drives ulceration.^[1][5]

Why it happens — microangiopathy, degenerate collagen, a palisade

The pathogenesis is a triangle: microvascular injury, immune-mediated granulomatous inflammation, and connective-tissue degeneration. Diabetic microangiopathy and endothelial damage starve the pretibial dermis; the collagen degenerates (necrobiosis); and histiocytes line up in palisades around the damaged collagen, with plasma cells, lymphocytes and thickened vessels in attendance.^[1][2]

The yellow-brown colour is partly optical and partly structural — thinned epidermis, degenerate collagen, lipid-laden change, haemoglobin breakdown and visible vessels combining into the waxy ochre centre; the violaceous rim is the active inflammation. This is why intralesional steroid belongs in the rim, not the centre: injecting atrophy into atrophy only worsens it.^[2][3]

Histology face-off — NL versus granuloma annulare (the trap)

NL and granuloma annulare are both necrobiotic granulomatous dermatoses, so the histology can confuse — but the architecture and the clinic differ. NL has broad, tiered, horizontal zones of necrobiosis through the dermis (sometimes into subcutis), more plasma cells, more vascular wall thickening, and relatively little mucin. Granuloma annulare has smaller, focal palisading granulomas with abundant dermal mucin and appears as non-atrophic annular papules on the hands and feet.^[2]

The discriminator line: horizontal granulomas with plasma cells in a pretibial atrophic plaque favour NL; mucin-rich focal granulomas in a non-atrophic hand lesion favour granuloma annulare. The diagnosis is clinicopathological — the pathologist needs to know the biopsy came from a yellow atrophic shin plaque.^[2]

Face-off — the pretibial plaque differentials

^{[1] [2] [5]}

The classic trap: pretibial myxoedema is the most tempting wrong answer because both are yellow-waxy shin lesions — but the discriminator is texture. Myxoedema is thick, indurated, non-pitting and mucinous, usually with Graves ophthalmopathy; NL is thin, atrophic, shiny, telangiectatic and ulcer-prone. A shin plaque that is thick and swollen rather than thin and depressed points to thyroid dermopathy.^[5]

Assessment — describe the plaque, then check the feet

Assessment begins with a deliberate skin description — site, symmetry, size, colour, border, surface, atrophy, telangiectasia, scale, induration, ulceration, exudate, tenderness — and a gentle palpation. NL feels thin and atrophic centrally with a raised active edge; myxoedema feels thick and oedematous; morphea feels bound down and sclerotic.^[3]

The bedside examination must include the feet and vascular system, because diabetic neuropathy and angiopathy are responsible for diabetic foot syndrome. When the plaque has ulcerated, structure the workup like any leg ulcer with the ABCDE rule: individualised history, bacteriological testing, clinical examination, ancillary testing for perfusion, and biopsies of atypical areas.^[1][6]

Investigations — clinical when classic, biopsy when not

A classic NL plaque is a clinical diagnosis. Investigations answer four exam questions: is there diabetes or thyroid disease? is the diagnosis secure? is an ulcer complicated by vascular disease, infection or malignancy? is it safe to use immunomodulatory treatment?^[1][3]

^{[1] [3]}

Biopsy the active border, not the ulcer slough — the necrobiotic collagen and palisading granulomas live at the raised rim, and sampling only dead slough shows nothing. Dermoscopy (yellow-orange background, white scar-like areas, branching telangiectases) is supportive, not mandatory.^[2][4]

Management — protect, treat the rim, spare the centre, dress the ulcer

The realistic goal is to halt progression, calm the active rim, prevent ulceration, heal ulcers and relieve symptoms — not to promise cosmetic normalisation, because mature plaques contain irreversible dermal atrophy. The ladder runs: education and risk reduction for everyone, topical or intralesional therapy for the active border, steroid-sparing options when atrophy limits steroids, phototherapy or systemic therapy for extensive disease, and wound-care escalation for ulcers.^[3]

Where to treat is the viva point. Potent topical steroid and intralesional triamcinolone go into the raised inflammatory rim; long unsupervised steroid over the paper-thin centre worsens atrophy and ulcer risk. Tacrolimus 0.1 percent is the steroid-sparing option because it does not thin the skin, useful on thin plaques and for maintenance.^[3][7]

^{[3] [7] [10]}

Smoking cessation is a treatment, not a lifestyle afterthought — it is disease-modifying risk reduction for the microvascular perfusion and wound healing that NL ulceration depends on. Trauma avoidance is equally practical: shin guards for high-risk work or sport, electric clippers rather than a razor over lesions, moisturising, no adhesive tapes on plaques, and prompt dressing of minor erosions.^[3][6]

Ulcerated NL is a dual diagnosis — NL and a chronic lower-limb ulcer. Cleanse gently, use non-adherent dressings, balance moisture with foam or hydrofiber, protect the fragile periwound skin, and add compression only once arterial supply is confirmed adequate by ankle-brachial index. Treat true cellulitis (spreading erythema, warmth, purulence, systemic features), not colonisation. Surgery is not first-line — recurrence, graft failure and poor healing are real — but excision with split-thickness grafting is reserved for selected refractory ulcers after vascular, venous, smoking and infection factors are optimised.^[3][6]

How patients with NL come to harm (the preventable list)

• Steroid injected into the atrophic centre — worsening atrophy, telangiectasia and ulcer risk; treat the rim^[3]
• Missed squamous cell carcinoma in a chronic changing ulcer edge, dressed for months without a biopsy^[9]
• Compression applied before checking the arterial supply — ischaemic injury in a diabetic, arteriopathic limb^[6]
• False blame — the patient told poor diabetic control caused the plaque, when NL persists despite excellent HbA1c and erodes trust and adherence^[1][3]
• Aggressive debridement of an ulcer that is actually pyoderma gangrenosum or vasculitis — pathergy and worsening^[6]
• Biologic started without TB, hepatitis and HIV screening — reactivation of latent infection^[3]

Special populations

Diabetes: check HbA1c or fasting glucose, coordinate diabetic foot and vascular risk care, examine neuropathy and pulses — but explain that the plaque may persist despite excellent control.^[1]

Pregnancy: conservative care — trauma avoidance, emollients, non-adherent dressings, short potent topical steroid courses only when needed; defer phototherapy and systemic agents.^[3]

Children: rare, often a clue to type 1 diabetes; use the minimum effective topical, avoid steroid atrophy in growing skin.^[7]

Older adults: more venous and arterial disease, anticoagulants and skin fragility — do not assume a leg ulcer is purely inflammatory; assess vessels and malignancy before compression.^[6]

Immunosuppressed: atypical infection and mycobacterial disease enter the differential — biopsy with stains and cultures before systemic immunosuppression.^[2][3]

Prognosis, follow-up and counselling

NL is chronic and often slowly progressive; some plaques stabilise, some fluctuate, some persist for years, and complete spontaneous resolution can occur but is not predictable. Mature plaques rarely return to normal because dermal collagen and elastic support are lost. Prognosis is best when lesions are small, non-ulcerated, protected and treated while the rim is active; worst with ulceration, smoking, venous or arterial disease, neuropathy and repeated trauma.^[1][3]

Follow-up is structured around the activity of the rim and the integrity of the centre, not simply whether the plaque still exists. At each review measure size, photograph, note whether the border is still raised or violaceous, ask about new erosions or trauma, check for steroid atrophy if used, and inspect intralesional injection sites. Review at 6-12 weeks after starting local therapy; sooner if ulcerated. A chronic ulcer that is not shrinking despite correct care should prompt revisiting the differential and biopsying the edge, not another dressing prescription.^[3][9]

Counselling prevents two harms. False reassurance — the plaque is benign but fragile, and ulceration, infection or a changing edge needs prompt review. And false blame — because NL is linked to diabetes, patients assume poor control caused it; explain that diabetes is an association that affects wound healing, not a report card for HbA1c. That message builds trust and adherence to protective measures.^[1][3]

The mantra, and the memory device

^{[1] [2]}

The mantra: yellow atrophic shin plaque, three layers, screen for diabetes, treat the rim not the centre, and biopsy the changing ulcer edge.^[1][3]

Ward-round test — three stems, thirty seconds each

Stem 1 — yellow shin plaques in type 1 diabetes (answer)ShowHide

A 38-year-old with type 1 diabetes has bilateral shiny yellow-brown patches on the shins with central atrophy, telangiectasia and a violaceous rim; one has a shallow erosion after a knock. What is it, and what do you tell her about her sugars? Model: Necrobiosis lipoidica, classic morphology. Screen HbA1c and thyroid disease, examine pulses and neuropathy, and dress the erosion with a non-adherent dressing. The counselling point examiners want: diabetes is a strong association, but tight glucose does not reliably clear established NL — so optimise diabetes for overall health and wound healing, do not promise the plaque will fade, and do not let her blame herself. Treat the active rim with a short potent topical or intralesional triamcinolone, never the atrophic centre.^[1][3]

Stem 2 — the wrong shin diagnosis (answer)ShowHide

A 55-year-old with Graves disease has firm, waxy, non-pitting plaques on both shins with a peau d'orange surface and no atrophy. Is this NL? Model: No — this is pretibial (thyroid) myxoedema, and the discriminator is texture: thick, indurated, non-pitting and mucinous rather than thin, atrophic, shiny and telangiectatic. Confirm with TSH, free T4 and TSH-receptor antibodies; biopsy shows dermal mucin. Look for the Graves triad (ophthalmopathy, dermopathy, acropachy). Treating it as NL — injecting steroid into a plaque that is not atrophic — misses the thyroid disease.^[5]

Stem 3 — the ulcer that will not heal (answer)ShowHide

An NL ulcer on the shin has been dressed weekly for four months; the edge is now raised, rolled and bleeding in places. Next step? Model: Biopsy the viable suspicious edge to exclude squamous cell carcinoma — a raised, rolled, bleeding, hyperkeratotic or enlarging edge in a chronic NL ulcer is the can't-miss complication, and continued dressing changes without tissue diagnosis are the error. At the same time reassess vascular supply and venous disease and review the differential (pyoderma gangrenosum, vasculitis, arterial disease). Only after histology and perfusion are sorted do you decide on wound care, compression or excision with grafting.^[6][9]

References10ShowHide

1. [1]Lima AL, Illing T, Schliemann S, et al. Cutaneous Manifestations of Diabetes Mellitus: A Review Am J Clin Dermatol, 2017.PMID 28374407
2. [2]Terziroli Beretta-Piccoli B, Mainetti C, Peeters MA, et al. Cutaneous Granulomatosis: a Comprehensive Review Clin Rev Allergy Immunol, 2018.PMID 29352388
3. [3]Erfurt-Berge C, Renner R, Peckruhn M, et al. S1-Guideline for diagnosis and therapy of necrobiosis lipoidica J Dtsch Dermatol Ges, 2026.PMID 41420334
4. [4]Errichetti E, Stinco G. Dermoscopy in General Dermatology: A Practical Overview Dermatol Ther (Heidelb), 2016.PMID 27613297
5. [5]Lause M, Kamboj A, Fernandez Faith E. Dermatologic manifestations of endocrine disorders Transl Pediatr, 2017.PMID 29184811
6. [6]Dissemond J, Placke JM, Moelleken M, et al. The Differential Diagnosis of Leg Ulcers Dtsch Arztebl Int, 2024.PMID 39115274
7. [7]Schiefer-Niederkorn A, Sadoghi B, Binder B. Necrobiosis lipoidica in childhood: a review of literature with emphasis on therapy J Dtsch Dermatol Ges, 2023.PMID 37401158
8. [8]Liu MJ, Li J. Necrobiosis Lipoidica N Engl J Med, 2024.PMID 38169491
9. [9]Vasari L, Simetić L, Kuna SK, et al. Cutaneous Squamous Cell Carcinoma Developing in Necrobiosis Lipoidica - A Case Report with Literature Review Dermatol Pract Concept, 2026.PMID 41912178
10. [10]Nihal A, Caplan AS, Rosenbach M, et al. Treatment options for necrobiosis lipoidica: a systematic review Int J Dermatol, 2023.PMID 37772666