What are the diagnostic criteria and treatment options for cutaneous lupus?

Diagnostic Approach for Cutaneous Lupus Erythematosus

Diagnosis of cutaneous lupus erythematosus requires evaluation by an experienced dermatologist with skin biopsy for histological confirmation, combined with classification into specific subtypes (acute, subacute, or chronic CLE) and exclusion of systemic lupus erythematosus through assessment of systemic involvement. 1, 2

Classification of CLE Subtypes

The three main categories must be distinguished based on clinical morphology and duration:

• Acute CLE (ACLE): Presents as localized malar "butterfly" rash or generalized eruption, commonly associated with systemic lupus erythematosus and prominent musculoskeletal symptoms 3
• Subacute CLE (SCLE): Highly photosensitive lesions on upper back, shoulders, neck, and anterior chest; frequently associated with anti-Ro/SSA antibodies and may be drug-induced 1, 3
• Chronic CLE (CCLE): Includes discoid LE (most common), verrucous LE, lupus profundus, chilblain LE, and lupus tumidus; characterized by indurated scaly plaques with scarring and pigmentary changes, typically on scalp, face, and ears 2, 3

Essential Diagnostic Workup

Skin Biopsy and Histopathology

• Skin biopsy is mandatory for histological analysis to confirm diagnosis 1, 2
• Repeat biopsy is indicated if clinical morphology changes or treatment fails 1
• Direct immunofluorescence may be performed when diagnosis remains uncertain 4

Laboratory Evaluation

Baseline autoantibody and complement testing should include: 5

• ANA (antinuclear antibodies)
• Anti-dsDNA
• Anti-Ro/SSA and anti-La/SSB antibodies
• Anti-RNP and anti-Sm
• Anti-phospholipid antibodies
• C3 and C4 complement levels

Additional baseline tests: 5

• Complete blood count (CBC)
• Erythrocyte sedimentation rate (ESR)
• C-reactive protein (CRP)
• Serum creatinine
• Serum albumin
• Urinalysis with urine protein/creatinine ratio

Clinical Assessment

Mucocutaneous lesions must be characterized as: 6

• LE-specific
• LE non-specific
• LE mimickers
• Drug-related

Use the Cutaneous Lupus Disease Area and Severity Index (CLASI) to quantify disease activity and damage 6, 1

Excluding Systemic Lupus Erythematosus

Renal Assessment

For patients with abnormal urinalysis or elevated creatinine: 5

• Obtain urine protein/creatinine ratio (or 24-hour proteinuria)
• Perform urine microscopy
• Order renal ultrasound
• Consider referral for kidney biopsy

Neuropsychiatric Screening

Monitor through focused history for: 5

• Seizures
• Paresthesiae and numbness
• Weakness and headache
• Depression
• Cognitive impairment (attention, concentration, word-finding, memory difficulties)

Systemic Monitoring

For patients with established CLE, regular monitoring for systemic involvement is essential 1

In inactive disease, repeat the following every 6-12 months: 5

• CBC, ESR, CRP
• Serum albumin and creatinine
• Urinalysis with protein/creatinine ratio
• Anti-dsDNA, C3, and C4 (to assess disease activity)

Treatment Algorithm

First-Line Treatment

For localized CLE lesions: 2

• Topical corticosteroids (mainstay of treatment) 7
• Topical calcineurin inhibitors 2, 3
• Photoprotection (essential for all patients due to high photosensitivity) 6, 7

For widespread or severe CLE, or lesions resistant to topical therapy: 2

• Antimalarials are first-line systemic treatment for all CLE subtypes (particularly hydroxychloroquine) 2, 3, 7
• Short-term corticosteroids may be added 2
• Antimalarials can be used safely in pregnant and pediatric patients 2

Second-Line Systemic Treatment

When antimalarials fail or are insufficient: 2

• Thalidomide (highly effective for chronic refractory discoid LE, but limited by teratogenicity and polyneuropathy risk) 2, 7
• Retinoids (particularly useful for hypertrophic LE) 2, 7
• Dapsone (drug of choice for bullous systemic LE and leukocytoclastic vasculitis) 7
• Methotrexate 2, 3

Third-Line Treatment

For refractory cases: 2

• Mycophenolate mofetil 2
• Azathioprine 6, 7

Fourth-Line Treatment

For localized, refractory CCLE lesions in cosmetically unacceptable areas: 2

• Pulsed-dye laser
• Surgical excision

For widespread CLE in patients with active SLE: 2

• Belimumab (particularly for recurrence of ACLE during corticosteroid tapering)

Critical Pitfalls to Avoid

• Do not rely solely on ANA testing for diagnosis, as it can be positive in other conditions 5
• Avoid mycophenolate mofetil, cyclophosphamide, and methotrexate in pregnancy 6
• Re-evaluate anti-Ro/SSA and anti-La/SSB antibodies before pregnancy due to risk of neonatal lupus and congenital heart block 6, 1, 5
• Monitor for thalidomide-induced polyneuropathy when using this agent 7
• Assess for drug-induced SCLE when evaluating new-onset subacute cutaneous lesions 3

Long-Term Management

At each follow-up visit, assess: 2

• Disease activity using validated indices
• Skin damage
• Quality of life
• Comorbidities (infections, atherosclerosis, hypertension, dyslipidemia, diabetes, osteoporosis) 6
• Adverse events from medications

Patient education regarding photoprotection, disease course, and treatment expectations is mandatory 2, 7