Commentary

Abstract

Cutaneous lesions of lupus erythematosus (LE) have been classified as specific or nonspecific for LE. Common specific lesions are acute cutaneous lupus erythematosus (ACLE), subacute cutaneous lupus erythematosus (SCLE), and chronic discoid lupus erythematosus (DLE). Acute cutaneous lupus erythematosus typically consists of a transient malar rash present in a patient with systemic disease; SCLE is a nonscarring, superficial, photosensitive papulosquamous eruption that is longer-lasting than ACLE and usually occurs in patients with mild or no systemic disease. Discoid lupus erythematosus is an intensely, inflammatory, indurated eruption leading to scarring and atrophy; most patients with DLE have little or no systemic disease. Both SCLE and DLE are usually distinguishable by cutaneous histology and by serology. Most SCLE patients have anti-Ro/SSA autoantibodies, and most DLE patients do not. In recent studies, we have found that immunofluorescence also distinguishes SCLE from DLE. Patients with SCLE have a distinctive deposition of IgG within the epidermis, while DLE patients have IgM or IgG at the dermal-epidermal junction (DEJ). Treatment for SCLE and DLE commonly includes sun protection, local steroid therapy, and antimalarials. Sun protective measures are usually more effective in SCLE than in DLE, since many DLE patients are not particularly photosensitive.Uncommon specific cutaneous lesions of lupus include cutaneous lesions of neonatal lupus erythematosus (NLE), lupus panniculitis, and bullous eruption of systemic lupus erythematosus (SLE). Neonatal lupus erythematosus is a transient disease consisting in most cases of skin disease similar to that of SCLE in adults, or of complete congenital heart block, or both. Mothers of babies with NLE almost always have IgG anti-Ro/SSA autoantibodies that cross the placenta and may be involved in the pathogenesis of NLE. For cutaneous lesions of NLE, sun protection and mild topical steroids are used.Lupus panniculitis is an uncommon inflammatory lesion of the subcutaneous tissue that may result in disfiguring depressed scars. Antimalarials remain the treatment of choice for most patients. Bullous eruption of SLE is an unusual phenomenon that may be related in many patients to the presence of antibodies to the basement membrane zone, particularly to the epidermolysis bullosa acquisita (EBA) antigen. Many patients with this eruption have responded well to dapsone.A critical question for patients who present with cutaneous lupus is whether systemic disease is present. In addition to history and physical exam, certain laboratory tests may be helpful. These include, but are not limited to, antinuclear antibodies (ANA), ANA profile (including antinative DNA and anti-Sm antibodies), complete blood count, platelet count, urinalysis, and complement levels. Examination of uninvolved skin for immunoglobulin deposition may be helpful except in the case of SCLE, where even patients who do not have systemic disease may have IgG and IgM in uninvolved skin.The pathogenesis of cutaneous lupus, or of LE in general, is not known. Autoantibodies are the most characteristic laboratory abnormality and are probably involved in the pathogenesis of LE. The specificity of the autoantibodies may be important in determining the clinical findings. Complement, inflammatory cells, cytokines, estrogens, and ultraviolet light may also be important. Several genes, especially those involved in antigen recognition, may play a role in determining susceptibility. Additional factors, possibly including infectious agents, must be present for a genetically susceptible individual to produce autoantibodies and develop LE.