Lupus erythematosus

Lupus erythematosus represnts a spectrum of cutaneous disease from scarring (discoid) to multisystem (systemic).

Aetiopathogenesis

There is increasing evidence that the induction of autoantibodies against self-proteins derives from an impaired ability to clear dying (apoptotic) cells. Both genetic (human leucocyte antigen (HLA)) and environmental (toxins, drugs, UV radiation, viruses) factors have been implicated in disease pathogenesis.

Pathology

Discoid lesions show epidermal atrophy, hyperkeratosis and basal layer degeneration. Subacute lesions show greater atrophy but the other features are less evident. Systemic lesions have similar changes with dermal oedema and fibrinoid change, inflammatory infiltrate and sometimes vasculitis. Direct immunofluorescence shows a ‘lupus band’ at the dermoepidermal junction in lesional systemic and discoid LE, but this is also found in approximately 20% of healthy individuals on sun-exposed skin.

Skin signs are found in 80%. The facial butterfly eruption (Fig. 1) is characteristic, but photosensitivity, discoid lesions, diffuse alopecia, mouth lesions and vasculitis also occur. Multisystem involvement with serological or haematological abnormalities must be demonstrated to diagnose systemic LE (Table 1). The female : male ratio is 8 : 1.

Fig. 1 Systemic LE.

The typical butterfly eruption is present on the face.

Table 1 Organ involvement in systemic LE

Organ	Involvement
Skin	Photosensitivity, facial rash, vasculitis, hair loss, Raynaud’s phenomenon
Blood	Anaemia, thrombocytopenia
Joints	Arthritis, tenosynovitis, calcification
Kidney	Glomerulonephritis, nephrotic syndrome
Heart	Pericarditis, endocarditis, hypertension
Central nervous system	Psychosis, infarction, neuropathy
Lungs	Pneumonitis, effusion

Subacute lupus erythematosus (60% ANA, 80% Ro, <5% dsDNA positive)

The skin involvement is usually on the neck, trunk and arms. The erythema is non-scarring and may be papulosquamous or annular and resolves with hypopigmentation and telangiectasia. Mouth ulceration, livedo reticularis, periungal telangiectasia and Raynaud’s phenomenon may also be noted. Multisystem involvement can be seen, but is usually mild.

Discoid lupus erythematosus (35% ANA, 2% Ro, <5% dsDNA positive)

One or more round or oval plaques appear on the face, scalp or hands (Fig. 2). The lesions are well demarcated, red, atrophic, scaly and show keratin plugs in dilated follicles. Scarring leaves alopecia on the scalp and hypopigmentation in those with a pigmented skin. Remission occurs in over 50%. Internal involvement is not a feature, and only 6% develop systemic LE. Women outnumber men by 2 : 1.