Cutaneous manifestations of systemic lupus erythematosus

Overview

•Discoid lupus erythematosus (DLE) - well-defined, indurated, erythematous/hyperpigmented plaques with adherent scaling, follicular plugging, and central atrophy; heals with atrophic scarring and dyspigmentation (central hypopigmentation, hyperpigmented rim); predominantly affects face and scalp

•Malar (butterfly) rash - erythematous flush across cheeks and nose bridge, sparing the nasolabial folds; photosensitive, non-scarring

•Subacute cutaneous lupus (SCLE) - widespread photosensitive rash; annular plaques or papulosquamous eruption; V-distribution on neck/upper chest/arms; non-scarring; associated with anti-Ro (SSA) antibodies

•Photosensitivity - present in virtually all subtypes; UV exposure worsens or triggers lesions

•Scarring alopecia - permanent; seen in scalp DLE (follicle destruction is irreversible). Distinct from non-scarring diffuse alopecia of systemic SLE

•Oral ulcers - typically painless, on hard palate or buccal mucosa

•Drug-induced SCLE - caused by thiazide diuretics, terbinafine, calcium channel blockers, proton pump inhibitors; anti-Ro positive; resolves on drug withdrawal

Investigations

🥇 First-line

•ANA - positive in >95% of systemic SLE; often negative in isolated DLE. Positive ANA in DLE should prompt investigation for systemic SLE

•Anti-dsDNA - highly specific for SLE (>95%); titres correlate with disease activity

•Anti-Ro (SSA) - positive in majority of SCLE; associated with neonatal lupus

🏆 Gold standard

•Skin biopsy with direct immunofluorescence (lupus band test) - granular IgG, IgM, complement deposition at dermo-epidermal junction; biopsy shows interface dermatitis and follicular plugging in DLE

Differential diagnosis

🎯

DLE key features to recall: erythematous papule → expands into well-defined scaly plaque with central atrophy and adherent scaling → photosensitive → scarring on healing. Nasolabial sparing distinguishes malar rash from rosacea.

Management

🥇 First-line

•Sun protection - SPF 50+ broad-spectrum sunscreen, UV-protective clothing; applies to all subtypes

•Topical corticosteroids - moderate-to-potent (e.g. betamethasone valerate 0.1%) for active DLE plaques and localised SCLE

•First-line (facial/sensitive areas): Topical calcineurin inhibitors (tacrolimus or pimecrolimus) - avoid steroid atrophy on face

🥈 Second-line

•Hydroxychloroquine - backbone systemic agent; inhibits TLR signalling; reduces flare frequency; requires annual ophthalmological review (retinopathy risk)

•Prednisolone - short courses for acute flares or widespread disease

🥉 Third-line

•Methotrexate, mycophenolate mofetil, or azathioprine - refractory disease or co-existing systemic SLE

Complications

•Scarring alopecia - permanent; hair follicle destruction irreversible in scalp DLE

•Progression to systemic SLE - ~5-10% of isolated DLE; higher risk if ANA-positive at diagnosis

•Squamous cell carcinoma - rare but recognised within chronic DLE scarring plaques; biopsy any non-healing ulcerated lesion