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ESSENTIALS OF DIAGNOSIS
Localized violaceous red plaques, usually on the face and scalp.
Scaling, follicular plugging, atrophy, dyspigmentation, and telangiectasia of involved areas.
Distinctive histology.
Photosensitivity.
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GENERAL CONSIDERATIONS
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Common forms of cutaneous lupus include chronic cutaneous lupus erythematosus (CCLE), typically chronic scarring (discoid) lupus erythematosus (DLE), and erythematous nonscarring red plaques of subacute cutaneous LE (SCLE) (eFigure 6–40) (eFigure 6–41). All occur most frequently in photoexposed areas. Permanent hair loss and loss of pigmentation are common sequelae of discoid lesions. Systemic lupus erythematosus (SLE) is discussed in Chapter 20-07. Patients with SLE may have DLE or SCLE lesions.
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A. Symptoms and Signs
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Symptoms are usually mild. The lesions consist of violaceous red, well-localized, single or multiple plaques, 5–20 mm in diameter, usually on the head in DLE and the trunk in SCLE. In DLE, the scalp, face, and external ears (conchal bowl) may be involved (eFigure 6–41). In discoid lesions, there is atrophy, telangiectasia, central depigmentation, a hyperpigmented rim, and follicular plugging. On the scalp, significant permanent hair loss may occur in lesions of DLE. In SCLE, the lesions are erythematous annular or psoriasiform plaques up to several centimeters in diameter and favor the upper chest and back.
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B. Laboratory Findings
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In patients with DLE, the possibility of SLE should be considered if the following findings are present: positive antinuclear antibody (ANA), other positive serologic studies (eg, anti-double-stranded DNA or anti-Smith antibody), high erythrocyte sedimentation rate, arthralgias/arthritis, hypocomplementemia, widespread lesions (not localized to the head), or nailfold changes (dilated or thrombosed nailfold capillary loops). Patients with marked photosensitivity and a picture otherwise suggestive of lupus may have negative ANA tests but are positive for antibodies against Ro/SSA or La/SSB (SCLE).
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DIFFERENTIAL DIAGNOSIS
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The diagnosis is based on the clinical appearance confirmed by skin biopsy in all cases. In DLE, the scales are dry and “thumbtack-like” and can thus be distinguished from those of seborrheic dermatitis and psoriasis (eFigure 6–13). Older lesions that have left depigmented scarring or areas of hair loss will also differentiate lupus from these diseases. Ten percent of patients with SLE have discoid skin lesions, and 5% of patients with discoid lesions have SLE. ...