discoid lupus (chronic cutaneous lupus erythematosus)

Introduction

Discoid lupus refers to scarring skin rash.

Epidemiology

• age 20-45 years
• females > males
• possibly more severe in blacks
• major cause of cutaneous lupus erythematosus

Pathology

dermatopathology

• epidermis: hyperkeratosis, atrophy, follicular plugging, liquefaction degeneration of the basal layer
• strong PAS staining of thickened epidermal basement membrane
• dermis: edema, dilation of small vessels, perifollicular infiltrate of lymphocytes & histiocytes
• immunofluorescence
  • granular deposits of IgG > IgM at dermal-epidermal junction
  • active lesions not recently treated with glucocorticoids
  • negative in old lesions & normal skin (regardless of sun exposure): contrast to SLE where IgG deposits found in normal sun-exposed skin (70-80%) & non-exposed skin (50%)

Clinical manifestations

• atrophic depigmented & erythematous plaques with a surrounding rim of hyperpigmentation
• early lesions: sharply marginated papules & plaques with adherent scales on sun-exposed skin
• late lesions:
  • atrophy & depression of lesions with slightly raised border
  • persistent localized erythema containing telangiectasias
  • adherent scales
  • follicular plugging
  • scarring, marked if untreated
• active lesions are bright red (erythematous), old lesions may be pink, white or hyperpigmented (violaceous)
• lesions generally asymptomatic, but may be slightly pruritic
• sites of predilection: face & scalp, ears, dorsa of forearms, hands, fingers, toes, less frequently trunk
• scarring alopecia
• duration of lesions months to years
• < 5% have mucous membrane involvement
• not associated with systemic lupus erythematosus, thus may be few if any manifestations of systemic lupus
• nasolabial folds may not be spared

* images

Laboratory

• anti-nuclear antibody in serum
  • low incidence of ANA in low titer 1:16
• complete blood count (CBC): occasional leukopenia
• skin biopsy
• urinalysis (rule-out systemic lupus erythematosus with renal involvement)

Complications

• 5-15% risk of systemic lupus erythematosus

Differential diagnosis

• actinic keratosis
• psoriasis
• polymorphous light eruption
• lichen planus
• lupus vulgaris (systemic lupus erythematosus with discoid lesions)
• tinea facialis
• alopecia areata (complete loss of hair, no visible effect on skin)

Management

• topical corticosteroids
• intralesional triamcinolone acetonide 3-5 mg/mL
• topical tacrolimus, topical pimecrolimus
• hydroxychloroquine 100 mg PO QD, up to 6.5 mg/kg/day, plus (if needed) quinacrine hydrochloride 100 mg PO QD
  • some evidence that hydroxychloroquine may prevent progression to systemic lupus erythematosus
• etretinate 1 mg/kg/day (severe discoid lupus)
• anifrolumab (investigational)
• prevention:
  • topical sunscreens (SPF 30 or higher)
  • protective clothing
• prognosis:
  • only 5-10% may develop SLE
  • complete remisson in 50%
  • remissions less frequent with generalized lesions (<10%)

More general terms

• cutaneous lupus erythematosus

More specific terms

• lupus panniculitis (lupus erythematosus profundus)