Cutaneous lupus erythematosus

Meet the patient

A 28-year-old woman returns from a beach weekend with rings on her chest and shoulders — annular, polycyclic, sun-shaped, leaving dyspigmentation as they expand. She is well in herself. ANA is positive at 1:320 and anti-Ro/SSA lights up the immunoblot. Biopsy shows basal vacuolar change and dermal mucin; direct immunofluorescence shows a granular band at the dermo-epidermal junction.[1]

The two questions that settle her next year are the two that settle every CLE clinic: will this scar? (DLE yes, SCLE and ACLE no) and is there systemic disease underneath? (ACLE always, SCLE sometimes, DLE rarely). Hold those two axes — scarring and systemic — and the whole classification folds flat.[1]

One umbrella, three faces, one drug list

CLE is every dermatological manifestation of lupus, and the 2018 Düsseldorf classification sorts them by the two questions juniors fumble: does it scar, and does it ride with SLE. Düsseldorf splits the skin disease into SLE-specific lesions (the interface-dermatitis family: ACLE, SCLE, CCLE) and SLE-non-specific lesions (vasculitis, livedo, Raynaud's, non-scarring alopecia), then carves out drug-induced lupus as its own beast.[1][4]

The SLE-specific family is three morphological clans, and the scarring-and-systemic axes place each one:[1][9]

[1]

Drug-induced lupus is two different diseases wearing one label, and the skin tells them apart. Systemic DILE is anti-histone positive (about 95 percent), driven by procainamide, hydralazine or isoniazid, and spares the skin. Drug-induced SCLE is anti-Ro/SSA positive, triggered by terbinafine, thiazides, calcium-channel blockers, TNF inhibitors and proton-pump inhibitors, and looks identical to idiopathic SCLE — so identical that the only clue is the medicine chart.[7]

A consultant confession: CLE is conserved across species. The Olivry veterinary review documents the same UV-driven interface dermatitis and lupus band in dogs — canine discoid lupus is the comparative model that first taught dermatologists how antimalarials quiet this disease. Read it for the mechanism, even if you never treat a dog.[3]

[1]

How common, who, and why it flares

CLE is common, female-skewed and unkind to skin of colour, and the single most examinable environmental trigger is the one the patient can change. Roughly 4 per 100 000 adults per year in European and North American registries, cumulative prevalence around 40 per 100 000. Cutaneous disease is the second commonest manifestation of SLE after arthritis, and 70-85 percent of SLE patients develop skin lesions at some point.[2]

The demographics track the subtype, and the subtype tracks the hormones:[2]

• ACLE and SCLE peak at 20-40 years and skew female — about 3:1 for ACLE (SLE-driven) and 2-3:1 for SCLE.
• DLE is roughly 1:1, because it does not ride the same oestrogen amplification — a useful clue when a balding male scalp turns out to be discoid.
• DLE is the commonest CLE in skin of colour (Fitzpatrick IV-VI). In African, Afro-Caribbean, Hispanic and South Asian cohorts the erythema hides under melanin, follicular plugging and dyspigmentation dominate, and the disease is recognised late — after the follicles are already gone.[2]

The genetic and environmental handles a fellowship candidate must name:[4]

• HLA-DR3 and HLA-DR4 enrich SCLE; HLA-DRB1*1501 travels with DLE.
• Homozygous C1q deficiency is rare but brutal — about 90 percent develop a CLE-like disease before adolescence. C2 and C4 deficiency raise CLE/SLE risk too. These early complement components clear apoptotic debris; lose them and the skin turns lupus-like even without overt SLE.
• UVB (290-320 nm) is the most photosensitising band; UVA (320-400 nm) adds to it.
• Smoking doubles CLE risk and quietly wrecks hydroxychloroquine — the modifiable trap this topic keeps returning to.
• Drugs (terbinafine, thiazides, diltiazem, TNF inhibitors, PPIs) trigger about 20-30 percent of all SCLE.[4][7]

The engine — UV, apoptosis, interferon

CLE is the prototypical Type I interferon-driven, UV-triggered autoimmune skin disease. One environmental hit (UVB) meets genetic susceptibility and produces an interface dermatitis anchored at the basal layer and the dermo-epidermal junction.[1][4]

The UV-to-apoptosis loop is the whole story in one sentence: UVB breaks keratinocyte DNA, the cell apoptoses, and in susceptible people the apoptotic cargo is never cleared — so hidden autoantigens get displayed on the cell surface. UVB (290-320 nm) damages keratinocyte DNA and drives apoptosis with membrane blebbing. Defective early complement (C1q, C2, C4) fails to opsonise the blebs, so Ro/SSA, La/SSB, Sm, RNP, dsDNA, nucleosomes and histones flip to the outer leaflet where antigen-presenting cells and autoantibodies can see them.[4]

Plasmacytoid dendritic cells are the amplifier, and they run on Type I interferon. UV-damaged keratinocytes release CXCL9, CXCL10, CXCL11 and LL-37/DNA complexes that drag plasmacytoid dendritic cells into the dermis. These cells are the body's chief IFN-α and IFN-β factories; once lit, they drive a sustained interferon-stimulated-gene signature (MxA, ISG15, IFIT1, IFI44L, OAS1) — strongest in SCLE and LE tumidus, the two most photosensitive subtypes.[4]

Antibody, T-cell and immune-complex effectors then execute the basal layer. Anti-Ro/SSA binds the exposed antigen, flagging the keratinocyte for NK-cell antibody-dependent cytotoxicity and complement lysis; anti-Ro immune complexes are then swallowed by FcγR-bearing dendritic cells, feeding the interferon loop back on itself. CD4 Th1 and CD8 cytotoxic T cells sit at the junction killing basal keratinocytes, and the perivascular and periadnexal infiltrate runs deep into the dermis — a depth that separates DLE from the superficial band of lichen planus.[1][4]

The lupus band is the immune-complex footprint, and it lives at the basement membrane zone. Circulating anti-BMZ antibodies and complexes deposit as a continuous granular line of IgG, IgM, IgA and C3 on direct immunofluorescence — positive in lesional skin of about 70-90 percent of active DLE, and in non-lesional sun-exposed skin of about 50-80 percent of active SLE, where it mirrors systemic disease.[1]

Smoking is not a footnote here — it is a pharmacological saboteur of the first-line drug. Tobacco downregulates lysosomal accumulation of hydroxychloroquine and piles on a pro-apoptotic, pro-interferon stimulus; smokers need roughly twice the dose and respond about half as often. Tell the patient before you prescribe, not after.[4]

[4] [4]

The three faces in clinic

Examine the whole skin surface, the scalp, both conchal bowls, the oral cavity and every nailfold — partial examination misses scalp DLE scarring and oral plaques that change management. CLE rewards the examiner who looks everywhere; the diagnosis often lives in the ear and the palate the junior skips.[1][5]

ACLE — the butterfly that means active SLE

ACLE is never just a rash — it is a vital sign of systemic disease, and the nasolabial fold is the diagnostic hinge.[2]

• Malar (butterfly) rash: bilateral, symmetrical, oedematous erythema over cheeks and nasal bridge that spares the nasolabial folds — the single sign that separates it from rosacea and seborrhoeic dermatitis, which fill those folds. Photosensitive, non-scarring, resolves over weeks to months with SLE treatment, often leaving post-inflammatory hyperpigmentation in darker skin.
• Generalised ACLE: a dusky morbilliform photosensitive eruption on the upper chest, V of the neck, extensor forearms and dorsum of the hands — sparing the knuckles, the clue that points away from dermatomyositis.
• Bullous ACLE is rare; tense vesicles mean neutrophil-rich subepidermal blistering with anti-Type VII collagen antibodies.
• Every ACLE patient gets a full systemic work-up — anti-dsDNA, complement C3/C4, urinalysis, renal function, blood count — because the skin is reporting the kidney.[2]

SCLE — anti-Ro, annular, sun-shaped, non-scarring

SCLE is the photosensitive ring on the V of the chest in an anti-Ro/SSA-positive woman, and half of these patients are on their way to SLE.[1]

• Annular/polycyclic SCLE (about half): coalescing erythematous rings with raised scaly advancing edges and central clearing, growing centrifugally into polycyclic patterns on upper trunk and arms. They do not scar, but they leave stubborn dyspigmentation, especially in Fitzpatrick III-VI skin.
• Papulosquamous (psoriasiform) SCLE (about half): scaly erythematous plaques that mimic psoriasis but lack the Auspitz pinpoint-bleed sign — again in sun-exposed sites.
• Distribution is the diagnostic handle: V of the chest, upper back, shoulders, extensor forearms, lateral neck. The face is involved in only about 20 percent — the feature that separates SCLE from ACLE.
• Anti-Ro/SSA is positive in 70-90 percent; anti-La/SSB in 10-20 percent and usually alongside.
• Drug-induced SCLE is morphologically indistinguishable from the idiopathic form — the only clue is the medicine list and resolution within 4-8 weeks of stopping the culprit.[6][7]

DLE — three zones, one scar, forever

DLE is the scarring discoid plaque with three concentric zones, and the follicle it destroys does not grow back. That permanence is why DLE is treated aggressively, not casually.[1]

The active discoid plaque has three zones, read outside-in:[1]

1. Active raised violaceous border with adherent scale and follicular plugging — keratotic spicules filling the hair-follicle openings. Lift the scale and the plugs stay behind, projecting from the follicles like carpet tacks — the carpet-tack sign, almost pathognomonic.
2. Mid-zone of hyperpigmentation, telangiectasia and gradual depigmentation.
3. Central atrophic scarring — hypopigmented, "scarred white", and permanent.[5]

The three-zone plaque, the carpet-tack sign and the conchal-bowl lesion are the bedside triad that ends the differential:[1]

• Sites of predilection: scalp (scarring alopecia), external ears and conchal bowls (highly characteristic), malar eminences, nasal bridge, periorbital skin, vermilion border, neck, V of chest.
• Mucosal DLE: discoid plaques with radiating white striae on buccal mucosa, hard palate, gingiva and lips — leukoplakia-like, and a long-standing lesion can turn malignant.
• Localised DLE (head and neck only, about 85 percent) progresses to SLE rarely. Generalised DLE (above and below the neck) progresses in about 20 percent — the gap that mandates a systemic work-up.
• Dermoscopy is highly specific: yellow-white follicular plugs, white structureless scarring, peripheral pigment network and red vascular loops, with absent follicular ostia — the sign that separates scarring DLE from non-scarring mimics.[5]

Know the DLE variants or you will biopsy the wrong thing:[1]

• Hypertrophic (verrucous) DLE — thick verrucous plaques on extensor limbs, palms and soles; mimics keratoacanthoma or SCC, so biopsy to exclude malignant change.
• Linear DLE — follows Blaschko lines, usually unilateral; confused with linear lichen planus or linear psoriasis.
• Comedo-like DLE — central keratinous plugs resembling acne.
• Lichenoid DLE — overlap with lichen planus on wrists and oral mucosa.[1]

LE profundus — deep nodule, cup-shaped scar

LE profundus (panniculitis) is the one that lives in the fat, and its scar is a dent. Firm subcutaneous nodules or plaques with normal or mildly erythematous overlying skin heal with depressed lipoatrophy — cup-shaped atrophic scars on cheeks, upper arms, buttocks and trunk. Histology is lobular panniculitis with hyalinised fat necrosis and a lymphoplasmacytic infiltrate, so a deep incisional or wide-punch biopsy including subcutis is essential.[1]

The differential that must not be missed is subcutaneous panniculitis-like T-cell lymphoma (SPTCL) — both are lobular panniculitis, but SPTCL shows atypical CD8+ T cells with clonal TCR rearrangement, haemophagocytosis and systemic features. A panniculitis that will not settle gets a deep biopsy and a TCR clonality study.[1]

LE tumidus — urticarial plaque, no scale, mucin

LE tumidus is the most photosensitive CLE, and it hides its interface under a pile of mucin. Smooth, urticarial-like, non-scarring plaques without surface scale appear in sun-exposed sites; phototesting shows exaggerated photosensitivity. Histology shows striking dermal mucin with relatively subtle interface change, and the response to antimalarials is excellent.[1]

Chilblain LE — perniosis that will not leave

Chilblain LE is perniosis that outstays winter, often in an anti-Ro/SSA-positive patient. Violaceous, cold-induced tender nodules and plaques on toes, fingers, heels, nose and ears resemble idiopathic chilblains but persist beyond the cold season and may ulcerate. Anti-Ro/SSA is positive in about half. The rare familial Aicardi-Goutières-like chilblain LE sits on a TREX1 gain-of-function mutation with constitutive Type I interferon activation.[1]

Mucosal LE — the oral plaque that can turn malignant

Oral DLE is the commonest mucosal CLE, and a non-healing lesion is a biopsy for cancer, not a flare. Discoid or lichenoid plaques on buccal mucosa, palate, gingiva, lip vermilion and occasionally tongue show radiating white striae and central ulceration; palatal erythema with central ulceration is characteristic. Nasal-septal perforation and xerostomia (Sjögren overlap) may coexist. About 3-5 percent of long-standing oral or lip DLE develops squamous cell carcinoma, so biopsy any lesion unhealed at 4-6 weeks.[1]

SLE-non-specific skin — the supporting cast

These lesions are not CLE-specific, but they flag systemic activity and belong in the exam answer. Non-scarring diffuse alopecia (lupus hair), periungual capillary dilatation and dropout on nailfold capillaroscopy, Raynaud's phenomenon, livedo reticularis, leucocytoclastic vasculitis with palpable purpura, urticarial vasculitis and bullous LE (anti-Type VII collagen) all support systemic disease even when they are not interface dermatitis.[2]

The mimics — and the one discriminator each

CLE collects mimics across every body region; this table is the SAQ backbone — one discriminator per row is what earns the marks.[1]

[1]

Read the biopsy — interface, mucin, and the lupus band

The unifying lesion is interface dermatitis at the basal layer, and the single most useful stain is the one for mucin. A lesional punch from the active edge (not the scarred centre) is the gold standard.[1][4]

On H&E, all CLE subtypes share five findings, and dermal mucin is the discriminator:[1]

• Basal-layer vacuolar degeneration — vacuolisation of basal keratinocytes with pyknotic nuclei; the lesion that names "interface dermatitis".
• Hyperkeratosis and follicular plugging — most pronounced in DLE, the histological substrate of the carpet-tack sign.
• Epidermal atrophy with effaced rete ridges in chronic lesions; acanthosis occasionally in hypertrophic DLE.
• Perivascular and periadnexal lymphocytic infiltrate running deep into the dermis — the depth that separates DLE from superficial lichen planus. CD4 Th and CD8 Tc cells predominate.
• Dermal mucin — glycosaminoglycans (mostly hyaluronic acid) between collagen bundles, feathery blue-grey on H&E, staining strongly with colloidal iron or Alcian blue. Mucin is the single feature that separates CLE from lichen planus and every other interface dermatitis.[1]

Each subtype has one histological fingerprint:[1][4]

[1]

The lupus band test is direct immunofluorescence, and the trick is where you biopsy.[1]

• Technique: a 4-mm punch from the lesional active edge (positive in about 70-90 percent of active DLE and 40-50 percent of SCLE), or from non-lesional sun-exposed skin such as the volar forearm (positive in about 50-80 percent of active SLE, 30 percent in remission). Transport in Michel's medium or snap-freeze.
• Appearance: a continuous granular band of IgG, IgM and C3 (sometimes IgA, fibrinogen) along the dermo-epidermal junction.
• Pitfall: sun-damaged skin, dermatoheliosis and rosacea give a false-positive band — improve specificity by biopsying non-sun-exposed (buttock) non-lesional skin.
• Versus bullous pemphigoid: BP gives a linear IgG/C3 band that salt-splits to the epidermal side; CLE is granular and does not split.[1]

In SCLE and LE tumidus the interferon signature is visible on staining — MxA and ISG15 are upregulated in keratinocytes, supportive stains for equivocal cases.[4]

The work-up — confirm, stage, subtract a drug, score

Every CLE patient gets the same four-part work-up: confirm with biopsy and DIF, stage for systemic disease, hunt a drug trigger, and baseline the activity with CLASI.[2][9]

The autoantibody panel reads differently by subtype, and the pattern is the exam answer:[2]

• ANA by IIF on HEp-2 cells: positive in about 70-90 percent of ACLE, 70 percent of SCLE and only 20 percent of isolated DLE. A negative ANA does not exclude CLE — confirm with biopsy.
• Anti-Ro/SSA (TRIM21, 52 kDa and 60 kDa): positive in 70-90 percent of SCLE, about 30 percent of DLE, 50 percent of Sjögren's and about 95 percent of neonatal lupus. It is the antibody of the photosensitive-to-CHB axis.
• Anti-La/SSB: 10-20 percent of SCLE, usually riding with anti-Ro.
• Anti-U1-RNP: mixed connective tissue disease (Sharp) overlap with CLE-like skin.
• Anti-Sm: highly specific for SLE but only 5-20 percent sensitive — a positive counts as an SLE criterion.
• Anti-dsDNA: SLE-specific; rising titres track flares and nephritis. Confirm specificity with Crithidia luciliae IIF.
• Antiphospholipid antibodies: lupus anticoagulant, anti-cardiolipin, anti-β2-glycoprotein I — request for thrombosis, recurrent miscarriage or secondary APS.
• Complement C3 and C4: low in active SLE (consumed); persistently low C4 with normal C3 raises C1q deficiency.
• Full blood count: autoimmune haemolytic anaemia (Coombs-positive), leucopenia, lymphopenia, thrombocytopenia — all SLE criteria.
• ESR and CRP: ESR up with CRP normal (the discordance) supports an SLE flare over infection.
• Renal assessment: urinalysis with microscopy (proteinuria, RBC casts), protein-to-creatinine ratio, creatinine, eGFR — every SLE patient at diagnosis and quarterly; active sediment triggers nephrology and possible renal biopsy.
• Skin biopsy — H&E and DIF: from the active advancing edge (not the healed centre), with a second biopsy from non-lesional sun-exposed forearm skin if SLE is in question.[1]
• Dermoscopy of DLE: yellow-white follicular plugs, white structureless scarring, peripheral pigment network, red dots, absent follicular ostia — supports the diagnosis without a biopsy.
• Phototesting (UVA and UVB minimal erythema dose) confirms photosensitivity in LE tumidus and SCLE when histology is subtle.[5]

Autoantibody frequencies at a glance: ANA (ACLE about 80 percent, SCLE about 70 percent, DLE about 20 percent); anti-Ro/SSA (SCLE 70-90 percent, neonatal lupus about 95 percent); anti-dsDNA (SLE-specific, under 50 percent); anti-Sm (5-20 percent); anti-histone (drug-induced SLE about 95 percent).[2]

CLASI is the validated CLE score, and a 4-point change in activity is the trial endpoint. The Cutaneous Lupus Erythematosus Disease Area and Severity Index splits into CLASI-A (activity: erythema, scale, oedema, mucosal lesions, recent alopecia) and CLASI-D (damage: dyspigmentation, scarring, scarring alopecia). It is validated for both DLE and SCLE, and a 4-point CLASI-A change is clinically significant.[2]

Management — the ladder, and the smoking trap

CLE treatment is a ladder built on five rungs: photoprotection, topical therapy, hydroxychloroquine, steroid-sparing immunosuppressants, and biologics or thalidomide for refractory disease. Drug-induced SCLE is the exception — stop the drug first.[1][4][9]

Rung 1 — photoprotection and smoking cessation (for every patient)

Sun protection is not advice — it is the foundation of treatment, and the smoker who will not quit will not respond to the first-line drug.[8]

• Sunscreen: broad-spectrum SPF 50+ with UVA (PPD at least one-third of SPF) and UVB cover, applied at 2 mg/cm² and reapplied every 2 hours outdoors; physical blockers (zinc oxide, titanium dioxide) for the highly photosensitive.
• Clothing: UPF 50+ long sleeves, wide-brimmed hats (over 7.5 cm brim), wraparound UV-blocking sunglasses — cuts UV exposure by 90-99 percent.
• Window films on car and home glass, avoid midday sun (10 am to 2 pm), beware reflective surfaces (water, sand, snow).
• Visible and blue light (400-500 nm) also trigger photosensitivity in darker skin — tinted (iron-oxide) sunscreens may be needed.
• Smoking cessation — smoking doubles the hydroxychloroquine dose requirement and halves the response rate; smokers respond in about 30 percent versus 70 percent in non-smokers.
• Vitamin D 800-1000 IU daily — sun avoidance makes deficiency the rule.[4][8]

Rung 2 — topical therapy (limited disease, or adjunct)

Topicals are for limited disease or as adjunct; the face gets a calcineurin inhibitor, the scalp gets a potent steroid.[1]

• Topical corticosteroids: potent (clobetasol propionate 0.05 percent) for scalp, body and acral skin; mid-potency (mometasone furoate, betamethasone valerate) for the face; cap courses at 2-4 weeks to avoid atrophy and telangiectasia.
• Topical calcineurin inhibitors (tacrolimus 0.1 percent ointment, pimecrolimus 1 percent cream): steroid-sparing, ideal for face and intertriginous CLE; twice daily; transient burning is the main side-effect.
• Intralesional triamcinolone acetonide 5-10 mg/mL (0.05-0.1 mL per cm², up to 1 mL per session) for thick or hypertrophic DLE plaques.
• Topical retinoids (tretinoin, adapalene) for hypertrophic DLE; irritating.
• R-salbutamol 0.5 percent cream (experimental β-2 agonist inhibiting keratinocyte apoptosis) — case-series evidence only.[1]

Rung 3 — hydroxychloroquine, the first-line systemic for everyone

Hydroxychloroquine is first-line for every CLE subtype, and the retinal screen is non-negotiable.[1][9]

• Hydroxychloroquine 200-400 mg/day — dose at 5 mg/kg/day or less by real body weight (6.5 mg/kg ideal body weight in obesity). Onset at 8-12 weeks; full benefit at 6 months. Baseline plus annual retinal screening with OCT, fundus autofluorescence and visual fields, annual after 5 years or sooner with risk factors (tamoxifen, renal failure, age over 65, dose over 5 mg/kg/day).
• Quinacrine (mepacrine) 100 mg/day — added to hydroxychloroquine for partial responders; no retinopathy (advantage over chloroquine); may yellow skin and sclera.
• Chloroquine 250-500 mg/day — occasional substitute in smokers or non-responders, but higher retinal toxicity; avoid long-term.[1][8][9]

Rung 4 — second-line immunosuppressants (steroid-sparing)

When hydroxychloroquine alone will not do, add a steroid-sparing agent matched to the patient — and check TPMT and G6PD before the relevant ones.[1]

• Methotrexate 10-25 mg weekly (oral or subcutaneous) with folic acid 5 mg 24-48 hours later — effective for SCLE, generalised DLE and articular SLE overlap; monitor LFTs every 4-8 weeks plus FBC and renal function; screen hepatitis B and C.
• Mycophenolate mofetil 2-3 g/day — useful for SLE-associated CLE; pregnancy-compatible if switched pre-conception; main toxicities GI intolerance, cytopenias, teratogenicity.
• Azathioprine 1-2 mg/kg/day — steroid-sparing; check TPMT before starting to avoid catastrophic myelosuppression in deficient patients.
• Acitretin 25-50 mg/day (or isotretinoin 0.5-1 mg/kg) — effective for hypertrophic and refractory DLE; highly teratogenic, with a 3-year post-stop contraception requirement.
• Dapsone 50-150 mg/day — best for bullous LE, urticarial vasculitis and SCLE; G6PD screen mandatory (haemolysis if deficient); watch for methaemoglobinaemia, agranulocytosis and sulphone hypersensitivity.[1]

Rung 5 — biologics and thalidomide (refractory disease)

Two biologics dominate refractory SLE-associated CLE, and thalidomide owns refractory DLE — each with a pregnancy-prevention string attached.[9]

• Belimumab (anti-BAFF/BLyS) 200 mg subcutaneous weekly — approved for SLE with active skin disease; best evidence in SCLE and ACLE; BLISS-52/76 and BLISS-LN showed mucocutaneous improvement.
• Anifrolumab (anti-Type I interferon receptor) 300 mg IV every 4 weeks — approved for moderate-to-severe SLE (TULIP-1, TULIP-2); rapid CLASI-A and BILAG mucocutaneous improvement; the most effective CLE biologic in SLE-associated disease.
• Rituximab (anti-CD20) 1 g weekly for 2 weeks, every 6 months — off-label for refractory CLE and SLE; BILAG registry data suggest a CLASI response in about half of refractory cases.
• Litifilimab (anti-BDCA2) — plasmacytoid-dendritic-cell-depleting antibody in trials with promising CLE outcomes.
• JAK inhibitors (baricitinib, tofacitinib, upadacitinib) — case-series evidence in refractory SCLE and DLE; class infectious and thrombotic risk.[4][9]

Refractory DLE — the thalidomide pathway

Thalidomide is the most powerful drug for refractory DLE, and its teratogenicity and neuropathy are the price.[1]

• Thalidomide 50-100 mg at night with a mandatory pregnancy-prevention programme (UK Preg-X, US S.T.E.P.S.); baseline and 6-monthly neuropathy monitoring (paresthesia, nerve conduction); response in about 80-90 percent of refractory DLE — the most effective agent for DLE scarring alopecia.
• Lenalidomide 5-10 mg/day — thalidomide analogue, less neuropathy but more myelosuppression and thrombosis.
• Apremilast (PDE4 inhibitor) 30 mg twice daily — small case series in refractory DLE.
• Dapsone — second-line alternative in the refractory pathway.[1]

Drug-induced SCLE — stop the drug

In drug-induced SCLE the drug chart is the treatment: withdraw the culprit and watch the rash resolve in 4-8 weeks. Work through the temporal probability map — terbinafine first, then thiazides, calcium-channel blockers, PPIs, TNF inhibitors, statins, antihistamines. Treat residual inflammation with a topical steroid or a short antimalarial course if withdrawal alone does not settle it.[7]

Special populations — where CLE bites hardest

CLE changes its teeth in pregnancy, childhood, old age and skin of colour; the anti-Ro pregnancy is the one that can stop a fetal heart.[4][8][10]

Pregnancy and neonatal lupus — the congenital heart block risk

An anti-Ro/SSA-positive mother can pass IgG across the placenta from about 16 weeks and permanently block the fetal cardiac conduction system. This is the single most serious preventable event in CLE, and it is why every anti-Ro-positive pregnancy is obstetrically co-managed.[10]

• Cutaneous neonatal lupus: about a quarter of affected neonates develop an annular or macular SCLE-like rash in sun-exposed sites within weeks of birth, photosensitive and self-resolving by 6-12 months as maternal antibodies clear.
• Congenital heart block (CHB): the gravest complication — irreversible, usually complete (third-degree), with an overall risk of 1-2 percent in a first anti-Ro pregnancy, rising to about 20 percent after one affected sibling. About 70-80 percent of children with CHB ultimately need a permanent pacemaker.
• Other neonatal features: cytopenias, hepatitis, hepatosplenomegaly, macrocephaly with lenticulostriate vasculopathy, hydrops fetalis.
• Obstetric management: serial fetal echocardiography at 16-26 weeks (weekly or fortnightly) for at-risk pregnancies; dexamethasone 4 mg/day (placenta-crossing) when first- or second-degree block is detected in utero (controversial).
• Pre-conception hydroxychloroquine 200-400 mg/day reduces CHB recurrence by about 50 percent (Izmirly, NEJM 2020; EULAR and AHA recommendation) and is safe throughout pregnancy.[10]

Drug safety in pregnancy — memorise the safe list and the teratogens:[9]

• Safe: hydroxychloroquine, low-dose prednisolone, azathioprine.
• Avoid: mycophenolate mofetil (teratogenic — switch to azathioprine pre-conception), methotrexate (teratogenic — 3-month washout), cyclophosphamide (severe teratogen), retinoids (severe teratogen; acitretin 3-year washout), thalidomide (severe teratogen, REMS programme).[9]

Childhood-onset CLE

Paediatric DLE is rare (about 3 percent of all DLE) and subtle — diagnose early and treat hard, because the scarring is for life. Investigate complement deficiencies (C1q, C2, C4) in any child with CLE; homozygous C1q deficiency mandates family counselling. Hydroxychloroquine is first-line, with retinal surveillance every 6 months (more often than adults). Avoid prolonged topical and systemic steroids.[4]

Older adults

In the elderly, CLE is often the presenting feature of SLE, and drug-induced SCLE hides in the polypharmacy. Reduce hydroxychloroquine for renal function (eGFR under 30 mL/min/1.73 m²) and start annual retinal screening from year 1, not year 5. Audit the drug list and the steroid load against comorbidities.[8]

Skin of colour

In Fitzpatrick IV-VI skin the erythema hides under melanin, so the threshold to biopsy must fall. Follicular plugging, dyspigmentation and scarring alopecia dominate; dermoscopy, biopsy and DIF carry the diagnosis when the redness cannot be seen. Counsel on visible-light photosensitivity and prescribe tinted (iron-oxide) sunscreens.[2]

Occupational and lifestyle factors

Outdoor workers, pilots, sailors, drivers and high-altitude or equatorial residents carry the highest UV load — and their drug list may be photosensitising. UV films on car and home windows, hats and high-SPF lip balms are essential. Review photosensitising drugs (doxycycline, tetracyclines, thiazides, amiodarone, NSAIDs, sulfonamides) in every anti-Ro/SSA-positive patient.[1]

Prognosis — the scarring axis decides most of it

CLE prognosis runs on one axis: does it scar? DLE scars forever; ACLE and SCLE do not. Around that, systemic transition and drug trigger shape the rest.[1][2][4]

• ACLE: resolves with SLE treatment; no cutaneous scarring, but post-inflammatory hyperpigmentation may linger for months, especially in darker skin. Course follows systemic activity.
• SCLE (idiopathic): chronic relapsing in about 80 percent; about half eventually meet SLE criteria. Severe visceral disease (proliferative nephritis) is uncommon. Hydroxychloroquine controls about 70 percent; relapse follows a photoprotection lapse.
• Drug-induced SCLE: excellent prognosis — resolves within 4-8 weeks of withdrawing the culprit, faster if sun is avoided.
• DLE (localised): about 85 percent stay skin-limited; permanent scarring alopecia, dyspigmentation and lip atrophy are the morbidity. Antimalarials within 6 months of onset preserve hair in active-edge lesions.
• Generalised DLE: about 20 percent transition to SLE — active surveillance justified.
• DLE scarring alopecia: irreversible once disease burns out — early aggressive therapy and UV minimisation are critical.
• LE profundus: chronic relapsing; lipoatrophy persists once active disease settles; cosmetic surgery suits inactive deep atrophy.
• LE tumidus: the most photosensitive subtype and highly antimalarial-responsive.
• Bullous LE: responds well to dapsone; heals in 4-8 weeks.
• Chilblain LE: may ulcerate, infect and destroy digits if untreated; responds to antimalarials, calcium-channel blockers and warming.
• Mucocutaneous LE: about 3-5 percent of chronic oral or lip DLE develops squamous cell carcinoma — biopsy any non-healing ulcerated DLE at any age.
• Mortality: CLE alone is rarely fatal; death tracks systemic organ disease (renal, CNS, cardiovascular) where SLE criteria are met, and SLE mortality now runs on cardiovascular disease and infection rather than active lupus.[1]

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Evidence, guidelines and regional differences

The CLE evidence base is review-led and guideline-anchored to EULAR 2023; know the guideline, the two biologics and the congenital-heart-block paper by author.[1]

• EULAR recommendations for SLE management, 2023 update (Fanouriakis et al., Ann Rheum Dis 2024) — sets antimalarial dosing, hydroxychloroquine ocular monitoring and the place of anifrolumab and belimumab in SLE with cutaneous involvement.[9]
• American Academy of Dermatology guidelines for DLE, SCLE and drug-induced lupus, referenced in 2024 reviews.[4]
• An Bras Dermatol 2023 (Vale and Garcia) — comprehensive etiopathogenic-clinical-therapeutic CLE review.[1]
• Am J Clin Dermatol 2023 (Niebel) — pathogenesis and future therapeutics: anifrolumab (anti-IFN-α receptor; TULIP-LN), litifilimab (anti-BDCA2) and JAK inhibitors.[4]
• Best Practice & Research Clinical Obstetrics & Gynaecology 2020 (Wainwright; Brito-Zeron, Izmirly, Ramos-Casals) — autoimmune-mediated congenital heart block, the evidence base for CHB screening and management.[10]
• Drugs & Aging 2024 (Heinly) — CLE in older populations, dosing adjustments and comorbidity-driven decisions.[8]
• BLISS-52 / BLISS-76 and EMBODY — belimumab and anifrolumab phase III trials, both meeting primary mucocutaneous endpoints (SELENA-SLEDAI, BILAG, CLASI-A).
• ACR/EULAR 2019 SLE classification criteria — confirmed cutaneous involvement as a major clinical domain (acute, chronic, oral ulcer, non-scarring alopecia).
• American Academy of Ophthalmology 2016/2023 — hydroxychloroquine retinal screening: baseline fundus with adjuncts, then annual screening after 5 years (sooner with major risk factors).[8]

Prevention — photoprotection is the cornerstone

Most CLE flares are UV-triggered within hours to days, so photoprotection is the single most cost-effective preventive intervention — and it works for primary and secondary prevention alike.[1][8]

• Daily broad-spectrum SPF 50+ sunscreen on all sun-exposed skin including ears, lips (SPF 30+ lip balm), neck and dorsum of hands; reapply every 2 hours outdoors and after swimming.
• Physical photoprotection: wide-brimmed hats, UPF 50+ clothing, long sleeves, UV-blocking sunglasses, UV films on car and home windows (windscreens block UVB but only partially block UVA — aftermarket films needed).
• Lifestyle: avoid direct sun from 10 am to 2 pm; cloud, water and snow all transmit UV and visible light; UVA passes ordinary glass, so an indoor day is not necessarily a safe day.
• Smoking cessation — the single most important modifiable factor for treatment response.[4]
• Drug stewardship — prescribe photosensitisers (terbinafine, thiazides, calcium-channel blockers, PPIs, TNF inhibitors) carefully in known anti-Ro/SSA-positive patients.[7]
• Vaccinations before immunosuppression: pneumococcal (PCV13 plus PPSV23), annual influenza (non-live), COVID-19 booster, shingles (Shingrix recombinant, non-live); avoid live vaccines during biologic therapy.
• Vitamin D 800-1000 IU daily for sun-avoidance deficiency.[8]
• Pregnancy vaccination: anti-Ro/SSA-positive mothers planning pregnancy receive recombinant shingles vaccine and annual influenza; mRNA COVID-19 vaccines are safe in CLE/SLE (flares rare and no worse than unvaccinated controls).
• Indoor-environment interventions: UV-blocking films for anti-Ro office workers; occupational assessment for pilots and cabin crew.

Exam pearls

[1] [1] [7] [1]

Ward-round test

Stem 1 — the photosensitive ring. A 29-year-old woman has annular polycyclic plaques on the V of her chest after a sunny holiday, anti-Ro/SSA positive, biopsy shows interface dermatitis with dermal mucin. Name the subtype, the antibody and the one systemic review she must have today.[1]

Answer

Subacute cutaneous lupus (SCLE), annular/polycyclic variant. The antibody is anti-Ro/SSA (70-90 percent). She needs ANA, anti-dsDNA, complement C3/C4, urinalysis and renal function — about half of SCLE patients meet SLE criteria, so the screen is non-negotiable.[1]

Stem 2 — the balding scalp plaque. A 45-year-old man has a coin-shaped plaque on the scalp with a raised violaceous border, central white scarring and absent hair follicles. Lift the scale and keratotic plugs stay behind. Name the sign, the subtype and whether the hair will regrow.[1]

Answer

Carpet-tack sign; discoid lupus (DLE); the hair will not regrow. DLE is the scarring subtype — three-zone plaque, follicular plugging, central atrophic scarring. The scarring alopecia is irreversible, so treatment (potent topical or intralesional steroid plus hydroxychloroquine) aims to preserve the remaining follicles.[1][5]

Stem 3 — the new rash after a new drug. A 60-year-old man started terbinafine six weeks ago and now has an annular SCLE-like rash. Biopsy and anti-Ro/SSA are consistent with SCLE. What is the single most important treatment step, and what confirms it?[7]

Answer

Stop the terbinafine. Drug-induced SCLE is morphologically indistinguishable from idiopathic SCLE — the diagnosis is temporal. Resolution within 4-8 weeks of withdrawal confirms it. Other culprits: thiazides, calcium-channel blockers, TNF inhibitors, PPIs.[7]

Stem 4 — the anti-Ro pregnancy. A 28-year-old anti-Ro/SSA-positive woman is planning pregnancy. What fetal investigation, what drug reduces the risk, and by how much?[10]

Answer

Serial fetal echocardiography at 16-26 weeks for congenital heart block; pre-conception hydroxychloroquine 200-400 mg/day reduces CHB recurrence by about 50 percent. The risk in a first anti-Ro pregnancy is 1-2 percent, rising to about 20 percent after one affected sibling; 70-80 percent of affected children need a permanent pacemaker.[10]

[1]

References

1. [1]Vale ECSD, Garcia LC. Cutaneous lupus erythematosus: a review of etiopathogenic, clinical, diagnostic and therapeutic aspects An Bras Dermatol, 2023.PMID 36868923
2. [2]Stull C, Sprow G, Werth VP. Cutaneous Involvement in Systemic Lupus Erythematosus: A Review for the Rheumatologist J Rheumatol, 2023.PMID 36109075
3. [3]Olivry T, Linder KE, Banovic F. Cutaneous lupus erythematosus in dogs: a comprehensive review BMC Vet Res, 2018.PMID 29669547
4. [4]Niebel D, de Vos L, Fetter T, et al. Cutaneous Lupus Erythematosus: An Update on Pathogenesis and Future Therapeutic Directions Am J Clin Dermatol, 2023.PMID 37140884
5. [5]Errichetti E, Stinco G. Dermoscopy in General Dermatology: A Practical Overview Dermatol Ther (Heidelb), 2016.PMID 27613297
6. [6]Trayes KP, Savage K, Studdiford JS. Annular Lesions: Diagnosis and Treatment Am Fam Physician, 2018.PMID 30216021
7. [7]He Y, Sawalha AH. Drug-induced lupus erythematosus: an update on drugs and mechanisms Curr Opin Rheumatol, 2018.PMID 29870500
8. [8]Heinly B, Allenzara A, Helm M, et al. Cutaneous Lupus Erythematosus: Review and Considerations for Older Populations Drugs Aging, 2024.PMID 37991658
9. [9]Fanouriakis A, Kostopoulou M, Andersen J, et al. EULAR recommendations for the management of systemic lupus erythematosus: 2023 update Ann Rheum Dis, 2024.PMID 37827694
10. [10]Wainwright B, Bhan R, Trad C, et al. Autoimmune-mediated congenital heart block Best Pract Res Clin Obstet Gynaecol, 2020.PMID 31685414