Cutaneous lupus erythematosus

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Cutaneous lupus erythematosus is a spectrum of interface dermatitis classified by morphology, duration, scarring and systemic association. Acute disease is closely linked to systemic activity. Subacute disease is highly photosensitive and often anti-Ro positive, with a meaningful drug-induced subgroup. Chronic discoid disease may remain cutaneous but creates irreversible scarring and dyspigmentation, especially on scalp and conchal ears. A person can have more than one subtype, and the skin label does not determine whether kidney, blood or neurological disease is present.

Ultraviolet exposure modifies keratinocyte antigens and immune signalling, which helps explain delayed flares after light exposure and the need for high-UVA protection even through windows. Smoking is associated with worse cutaneous activity and reduced antimalarial response. Hydrochlorothiazide, terbinafine, proton-pump inhibitors and other medicines can trigger an SCLE phenotype, but medication changes require prescriber coordination and an assessment of latency rather than reflex withdrawal.

Management balances inflammation control with prevention of permanent damage. An active erythematous scaly discoid edge contains salvageable follicles; a pale atrophic centre records lost structure. Photographs and activity-versus-damage measures are more useful than colour alone. Systemic assessment is repeated because organ disease can emerge after the skin diagnosis, while drug safety includes retinal, blood, liver, renal, infection and pregnancy planning.

Key points

Acute cutaneous lupus includes a photosensitive malar eruption that often spares nasolabial folds and usually tracks active systemic lupus rather than existing as an isolated diagnosis.
Subacute cutaneous lupus forms annular polycyclic or papulosquamous lesions on upper trunk and arms, commonly associates with anti-Ro antibodies and can be medicine induced.
Discoid lupus produces adherent scale, dyspigmentation, follicular plugging and atrophic scar on face, ears or scalp; destroyed hair follicles do not regrow.
In richly pigmented skin, active inflammation may appear violaceous, grey or hyperpigmented and permanent dyspigmentation may be more conspicuous than redness.
Assess every patient for systemic symptoms, blood pressure, urinalysis, FBC and renal function, then use ANA, dsDNA, ENA and complement according to phenotype and specialist pathway.
Biopsy an active representative lesion for routine histology; direct immunofluorescence can support selected uncertain cases but sun-exposed normal skin can create a nonspecific lupus band.
Core management is high-UVA broad-spectrum photoprotection, shade, clothing, smoking cessation and review of photosensitising or SCLE-associated medicines.
Use a site-appropriate potent topical corticosteroid or off-label tacrolimus for limited disease, with an application amount, stop date and infection review.
Hydroxychloroquine is the usual systemic foundation when topical care is insufficient, dosed no higher than 5 mg/kg actual body weight daily with retinal monitoring and renal-risk adjustment.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Autoimmune susceptibility

Genetic and immune-regulatory factors permit nuclear-antigen responses that damage photosensitive keratinocytes and sometimes multiple internal organs.

Ultraviolet exposure

UVA and UVB alter keratinocyte antigens and inflammatory signalling, provoking lesions after a delay rather than necessarily during exposure.

Medicine-induced subacute disease

Selected antihypertensive, antifungal, proton-pump and other medicines can trigger an anti-Ro-associated SCLE phenotype after variable latency.

Smoking-associated persistence

Smoking amplifies cutaneous activity and is associated with poorer antimalarial response, making supported cessation part of disease treatment.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Keratinocytes display nuclear antigen
Ultraviolet-stressed epidermal cells expose nuclear autoantigens and release inflammatory mediators that recruit lymphocytes to attack the dermal–epidermal junction.
2
Interface injury develops
Immune attack at basal epidermis produces vacuolar degeneration, scale and dyspigmentation shared by several cutaneous lupus subtypes.
3
Follicles are destroyed
Chronic discoid inflammation extends around follicular units, replacing them with scar and causing irreversible alopecia when control is delayed.
4
Systemic autoimmunity may coexist
The same immune susceptibility can affect kidney, blood, joints, nervous system, heart and lung independently of visible skin area.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Acute malar eruption

Fixed photosensitive cheek and nasal erythema or violaceous colour with relative nasolabial-fold sparing supports acute cutaneous lupus in a systemic context.

Annular subacute plaques

Polycyclic scaly rings over upper chest, back and extensor arms heal without scar but can leave long-lasting pigment change.

Papulosquamous subacute disease

Psoriasiform photosensitive plaques can mimic psoriasis, making distribution, anti-Ro context, medicines and biopsy important.

Discoid active edge

Adherent scale, follicular plugs and inflammatory pigment surround an atrophic scarred centre on face, ear or scalp.

Scarring alopecia

Loss of follicular openings with dyspigmented atrophy indicates permanent discoid destruction and requires prompt control at any active perifollicular edge.

Vasculitic or systemic warningRed flag

Retiform purpura, ulcers, digital ischaemia, oedema, hypertension, chest or neurological symptoms shifts urgency toward systemic organ disease.

Red flags requiring action

Rapidly ulcerating or vasculitic skin, digital ischaemia, extensive blistering, fever, mucosal disease, progressive scarring scalp loss or systemic symptoms requires urgent dermatology and rheumatology assessment.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Routine histology from an active lesionFirst step
Why
Confirm interface dermatitis, follicular involvement and mucin while excluding infection or malignancy.
Interpretation and limitations
Basal vacuolar change, lymphocytic inflammation and follicular plugging support cutaneous lupus but overlap with dermatomyositis and lichenoid disease; clinical subtype remains essential.
02
Direct immunofluorescence in selected cases
Why
Detect junctional immunoglobulin and complement when routine findings and clinical morphology remain uncertain.
Interpretation and limitations
A lesional lupus-band pattern can support diagnosis, but negative testing does not exclude disease and positive sun-exposed normal skin is less specific.
03
ANA, ENA, dsDNA and complement
Why
Support systemic classification and identify antibody phenotypes such as anti-Ro-associated subacute disease.
Interpretation and limitations
ANA is sensitive but nonspecific; dsDNA and low complement can accompany systemic activity, while antibody results alone neither diagnose the skin lesion nor justify immune escalation.
04
FBC, renal profile, blood pressure and urine protein
Why
Screen for silent cytopenia and renal involvement at diagnosis and follow-up.
Interpretation and limitations
Haematuria, casts, quantified protein, rising creatinine or hypertension requires urgent rheumatology and nephrology assessment regardless of skin area.
05
Medicine and light-exposure review
Why
Identify an SCLE-associated drug or ultraviolet pattern that can be modified safely.
Interpretation and limitations
Establish latency and indication and coordinate any withdrawal; persistence for weeks or months after stopping does not disprove a drug contribution.
06
Hydroxychloroquine retinal and safety baseline
Why
Prevent retinal and systemic harm before long-term antimalarial treatment.
Interpretation and limitations
Record actual weight, eGFR, ocular history, interacting medicines and retinal-monitoring timing; renal impairment and tamoxifen exposure increase toxicity risk.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Rosacea

Flushing, papules, pustules and telangiectasia centred on convex face without scarring or interface change favour rosacea over acute lupus.

Seborrhoeic dermatitis

Greasy scale in scalp, brows and nasolabial folds contrasts with the fixed photosensitive malar pattern that often spares those folds.

Psoriasis

Sharply demarcated plaques with silvery scale, classic extensor or scalp sites and nail change can mimic papulosquamous SCLE.

Dermatomyositis

Gottron papules, heliotrope change, nailfold abnormalities, muscle weakness and myositis antibodies support a related but distinct interface disease.

Cutaneous lymphoma or infection

Atypical infiltrated, ulcerated or treatment-resistant plaques require biopsy and organism studies rather than indefinite lupus escalation.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01First diagnostic sequenceSubtype the skin and screen the organsFirst stepA photosensitive, annular or scarring eruption suggests cutaneous lupus.

1Map distribution, scale, follicular openings, scar and pigment in neutral light, ask about light, smoking, medicines and systemic symptoms and photograph activity with consent.
2Biopsy an active representative site for routine histology and add correctly planned direct immunofluorescence only when it will resolve a meaningful uncertainty.
3Check blood pressure, FBC, renal and liver profile, urinalysis with quantified protein where abnormal and phenotype-led antibodies and complement, then refer to dermatology and rheumatology according to risk.

02First-line preventionReduce ultraviolet and smoke amplificationFirst lineCutaneous lupus is confirmed or strongly supported regardless of current treatment intensity.

1Use broad-spectrum high-UVA sunscreen on exposed skin with shade, tightly woven clothing, hats and window protection where relevant, reapplying by product and exposure instructions.
2Offer smoking-cessation support and review photosensitising and SCLE-associated medicines with their prescribers rather than stopping essential therapy abruptly.
3Address vitamin D risk, camouflage and mental health so rigorous photoprotection does not create deficiency, isolation or an impractical daily plan.

03Limited active diseaseSuppress inflammation before scar formsA small area of active acute, subacute or discoid disease has not produced major systemic involvement.

1Choose a potent topical corticosteroid for a thick discoid plaque or a safer site-specific potency for face and folds, with a defined quantity and review date.
2Use off-label topical tacrolimus for selected facial or flexural disease when steroid atrophy is a concern and exclude infection before applying immune suppression.
3Reassess active scale, erythema or violaceous change and follicular preservation within weeks; progressive scalp scar or wider disease warrants systemic treatment.

04Systemic skin controlUse hydroxychloroquine with retinal safeguardsDisease is widespread, scarring, recurrent or inadequately controlled by prevention and topical treatment.

1Record actual body weight, kidney function, eye and cardiac history, interactions, pregnancy plans and baseline retinal requirements before selecting no more than 5 mg/kg daily.
2EscalationReview adherence, smoking and response after several months rather than escalating after a few weeks; arrange retinal monitoring at the risk-based UK interval.
3For persistent damaging disease, specialists add methotrexate, mycophenolate or another phenotype-appropriate steroid-sparing treatment with blood, liver, infection and reproductive monitoring.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

Usual systemic foundation for widespread, recurrent or scarring cutaneous lupus and associated systemic lupus when not contraindicated.

Hydroxychloroquine

Take 200–400 mg by mouth once daily with food, using the lowest effective dose and never exceeding 5 mg/kg actual body weight per day.

Review macular disease, eGFR, tamoxifen, QT drugs, cardiomyopathy, hypoglycaemia and pregnancy context and arrange risk-based retinal monitoring. Skin response takes months and smoking can reduce efficacy.

Rapid local suppression of an active discoid or other inflammatory cutaneous lupus plaque before permanent damage develops.

Site-appropriate topical corticosteroid

Apply a thin layer once daily to active plaques for the prescribed two-to-six-week course, then stop, reduce or use intermittently only after review.

Match potency to face, scalp, ear, trunk or fold and monitor atrophy, telangiectasia, dyspigmentation and infection; avoid indefinite renewal and protect eyes and mucosa.

Steroid-sparing local immune treatment where thin skin makes corticosteroid atrophy particularly undesirable.

Tacrolimus 0.1% ointment for selected adult skin

Apply a thin layer twice daily to selected facial or flexural lesions under an explicitly off-label cutaneous-lupus plan and review response.

Explain off-label use, transient burning, infection and sun-protection requirements; avoid infected skin and review extensive use, immune compromise, pregnancy and failure with dermatology.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Permanent scar and dyspigmentation

Chronic discoid inflammation leaves atrophy, altered pigment and disfiguring scalp alopecia even after immune activity is controlled.

Systemic organ disease

Renal, haematological, neurological, cardiopulmonary and thrombotic lupus can arise silently or acutely and determine overall prognosis.

Squamous malignancy in scar

Longstanding hypertrophic or scarred discoid plaques have a small squamous-cancer risk, making new growth, ulcer or bleeding a biopsy indication.

Treatment toxicity

Topical atrophy, antimalarial retinopathy and systemic immunosuppressive infection, blood, liver and reproductive harm require structured monitoring.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Photograph the same active edges and record scale, induration and follicular openings separately from fixed scar and pigment every few months.
At each review ask about urine, oedema, pressure symptoms, chest, breathing, neurological, mucosal, joint, fever and blood-count features and check urine and renal markers at the risk-based interval.
For hydroxychloroquine document actual-weight dose, adherence, eGFR, interactions and retinal-screen attendance and investigate visual or cardiac symptoms promptly.
During topical therapy inspect facial, auricular and scalp skin for atrophy, telangiectasia, infection and continued inflammatory spread.
Review smoking support, sunscreen technique, occupational or window exposure, vitamin D and the psychological burden of visible dyspigmentation.
Escalate new scalp symptoms or loss of follicular openings quickly because established discoid scar cannot be repigmented or regrown reliably.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Subtype predicts but does not decide

Acute disease has the strongest systemic association and discoid the greatest scarring tendency, yet every patient still needs individual organ assessment.

Activity surrounds damage

In discoid disease, the scaly inflamed edge contains salvageable structures while a smooth pale centre records irreversible scar.

Pigment can hide inflammation

Violaceous or grey active change may blend with post-inflammatory hyperpigmentation in darker skin, making texture, symptoms and serial images essential.

Glass is not complete protection

UVA penetrates ordinary windows and can sustain occupational or driving exposure despite the absence of sunburn.

Antibody and lesion answer differ

Anti-Ro supports an SCLE phenotype and pregnancy counselling, while biopsy establishes what process is actually occurring in the sampled skin.

11Common pitfallsFrequent interpretation and management errors.

01
Calling all photosensitive facial redness a malar lupus rash without checking morphology, duration and systemic context.
02
Missing active discoid inflammation in deeply pigmented skin because it is not bright red.
03
Treating a positive ANA as proof that an unrelated skin eruption is cutaneous lupus.
04
Using potent topical corticosteroid indefinitely on face or ear without an activity and toxicity review.
05
Prescribing hydroxychloroquine above 5 mg/kg actual body weight or without retinal planning.
06
Managing scalp plaques cosmetically after follicular openings begin to disappear.