Introduction
Lupus erythematosus comprises a spectrum of autoimmune conditions ranging from cutaneous‑limited disease to systemic lupus erythematosus (SLE). Clinicians should recognize the distinct clinical phenotypes—discoid lupus erythematosus (DLE), subacute cutaneous lupus erythematosus (SCLE), and SLE—because they differ in prognosis, organ involvement, and management.
Epidemiology and Clinical Spectrum
DLE often presents with chronic, scarring cutaneous lesions and is more likely to remain skin‑limited; roughly 5–10% of DLE cases evolve into systemic disease. SCLE presents with non‑scarring annular or papulosquamous lesions, photosensitivity, and a lower risk of major organ involvement. SLE is multisystemic and has varied presentations, from mild mucocutaneous and arthritic disease to life‑threatening renal, neuropsychiatric, or hematologic involvement.
Pathogenesis: Key Concepts for Clinicians
Pathogenesis integrates genetic predisposition, hormonal influences, environmental triggers (notably ultraviolet radiation and certain medications), and immune dysregulation. Defective clearance of apoptotic cells and immune complex deposition activate complement and plasmacytoid dendritic cells, promoting a type I interferon response that drives B‑cell differentiation and autoantibody production (ANA, anti‑dsDNA, anti‑Sm). Complement deficiencies (eg, C1q) and select HLA alleles confer higher risk for severe disease.
Clinical Features by Type
- Discoid Lupus Erythematosus (DLE): Chronic, well‑demarcated erythematous plaques with adherent scale and follicular plugging, most commonly on sun‑exposed face and scalp. Lesions may scar and cause permanent alopecia when the scalp is involved. Systemic symptoms are usually absent.
- Subacute Cutaneous Lupus Erythematosus (SCLE): Annular or papulosquamous, non‑scarring lesions on sun‑exposed sites, pronounced photosensitivity, and frequent association with anti‑Ro/SSA antibodies. Systemic involvement is less common but patients may have arthralgia or mild serologic abnormalities.
- Systemic Lupus Erythematosus (SLE): Multisystem disease with variable manifestations: malar rash, photosensitivity, oral ulcers, non‑erosive inflammatory arthritis, serositis, nephritis, cytopenias, and neuropsychiatric features. Flares often follow environmental triggers (UV exposure, infections, certain drugs).
Diagnostic Approach
Suspect lupus when patients present with characteristic cutaneous lesions, unexplained cytopenias, proteinuria, serositis, or multi‑joint inflammatory arthritis. Initial investigations include:
- Antinuclear antibody (ANA): Sensitive but non‑specific; proceed to extractable nuclear antigen panels (anti‑Ro/SSA, anti‑La/SSB, anti‑Sm) and anti‑dsDNA if ANA positive.
- Complement levels (C3, C4): Useful biomarkers for disease activity, particularly in suspected nephritis.
- Urinalysis and urine protein quantification: Screen for renal involvement; follow with renal biopsy when indicated.
- Skin biopsy: For atypical lesions, to distinguish DLE/SCLE from other dermatoses and confirm interface dermatitis with follicular plugging.
Management Principles
Management is phenotype‑directed and includes photoprotection, topical and systemic therapy, and multidisciplinary care for systemic disease.
- Photoprotection: Broad‑spectrum sunscreen and behavioral counseling are foundational for all cutaneous lupus patients.
- Topical therapies: High‑potency topical corticosteroids or calcineurin inhibitors for localized cutaneous disease.
- Antimalarials: Hydroxychloroquine is first‑line systemic therapy for cutaneous and mild systemic disease; monitor for retinal toxicity.
- Systemic immunosuppression: Methotrexate, azathioprine, mycophenolate mofetil, or cyclophosphamide are used based on organ involvement and severity. Belimumab and rituximab are options for refractory disease.
- Drug‑induced lupus: Identify and discontinue the offending agent; most cases resolve after cessation.
Special Considerations
- Scalp involvement: Early dermatology referral and aggressive topical/systemic therapy may prevent scarring alopecia.
- Pregnancy: Preconception counseling is critical. Anti‑Ro/SSA antibodies increase risk for neonatal lupus and congenital heart block; manage antiphospholipid antibody positivity to reduce obstetric risk.
Follow‑up and Prognosis
DLE and SCLE often have favorable prognoses with appropriate management, though DLE can cause disfiguring scarring. SLE prognosis has improved substantially with modern therapy; however, organ damage accrues over time and requires regular monitoring (renal, cardiovascular, ophthalmologic for antimalarials), vaccination, and preventive care.
Clinical Takeaways
- Differentiate cutaneous‑limited lupus (DLE/SCLE) from systemic disease early to tailor investigations and follow‑up.
- Prioritize photoprotection and hydroxychloroquine for cutaneous disease.
- Screen routinely for renal, hematologic, and neuropsychiatric involvement in SLE and refer to specialists for organ‑threatening disease.
For a patient handout or a one‑page quick reference for primary care, I can generate a printable summary and diagnostic checklist—tell me which you’d prefer.
