Skin Disorders Guide

Diagnostic Hallmarks

1. Distribution: trunk, but palm and sole involvement IS characteristic when present
2. Target lesions
3. Papules and plaques are similar but less transient than those in urticaria

Clinical Presentation

Erythema multiforme is characterized by the presence of flat-topped, sharply marginated papules 1 to 2 cm in diameter. The color is generally duskier than the hright red of urticarial lesions. Typically, at least a few of the larger papules will be of the target type in which three concentric rings are found: an outermost red ring, a lighter-colored intermediate ring, and a central, dusky-colored bull’s-eye. Bullous changes, when they are present develop from the center of such lesions. The lesions of erythema multiforme seem to exist on a spectrum with those of urticaria. They differ from urticarial papules by being considerably less transient (they change in days rather than hours), by being a duskier red (less edema to “dilute” the redness), and by showing less tendency for coalescence and serpiginous outlines.

The lesions of erythema multiforme may occur anywhere on the body, but the presence of lesions on the palm and sole is quite characteristic. A search should be made for mucosal lesions, since the presence of such lesions may presage the development of Stevens-Johnson syndrome. The amount of pruritus that accompanies erythema multiforme varies from minimal to moderate. It is usually less troublesome than that which occurs in urticaria.

The diagnosis of erythema multiforme is made on the basis of clinical examination. Biopsies can be used to support a clinical diagnosis.

Atypical clinical Presentatians. Many patients present with a condition that exists between urticaria and erythema multiforme in clinical appearance. The flat-topped papules are bright red and show some tendency for coalescence. Unlike the lesions of urticaria, however, once present they remain unchanged for days. On the other hand, target lesions are not present, and mucous membranes are not involved. Such a picture is hardly multiform.

Erythema multiforme occurring with bullous changes, mucous membrane involvement, and fever is known as the Stevens-johnson syndrome . The etiology and pathogenesis are the same as for conventional erythema multiforme, but morbidity is considerably greater.

Toxic epidennal necrolysis of the Lyell type is a variant of erythema multiforme in which blister formation is tremendously extensive; sheets of skin lift off as might occur in a severe thermal burn. The clinical presentation is somewhat similar in appearance to that of the staphylococcal scalded skin syndrome (toxic epidermal necrolysis of the Ritter type), but the histologic site of blister formation is different, and there is considerably greater morbidity with the erythema multiforme variant.

Course and Prognosis

Most cases of erythema multiforme continue at an active level for 10 to 15 days, after which slow, spontaneous resolution occurs. Postinflammatory pigmentation may be left at the site of some lesions. Recurrent episodes are not common, except when the process is triggered by herpes simplex infections. Controversy exists as to whether or not a chronic, persistent form of erythema multiforme exists, but in most instances immunofluorescent studies suggest that “chronic” erythema multiforme is actually one of the immunobullous diseases such as pemphigoid.

Morbidity in erythema multiforme varies considerably. Few systemic symptoms and signs occur in most cases, but patients with Stevensjohnson syndrome and toxic epidermal necrolysis are quite ill, and death can occur.

Therapy

The lesions of erythema multiforme respond poorly to therapy . Patients with the more severe forms of the disease are usually treated with systemically administered steroids, but proof of efficacy and, for that matter, proof of safety are lacking. Milder cases do not require steroid therapy. Orally administered antihistamines may be of help when itching is a problem, but they will have little or no effect on the lesions themselves. Topical applications, including topically applied steroids, are not effective.