Erythema multiforme (EM) is the name applied to a group of hypersensitivity disorders, affecting mostly children and young adults, and characterized by symmetric red, patchy lesions, primarily on the arms and legs. The cause is unknown, but EM frequently occurs in association with herpes simplex virus, suggesting an immunologic process initiated by the virus. In half of the cases, the triggering agents appear to be medications, including anticonvulsants, sulfonamides, nonsteroidal anti-inflammatory drugs, and other antibiotics. In addition, some cases appear to be associated with infectious organisms such as Mycoplasma pneumoniae and many viral agents.
Erythema multiforme is the mildest of three skin disorders that are often discussed in relation to each other. It is generally the mildest of the three. More severe is Stevens-Johnson syndrome. The most severe of the three is toxic epidermal necrolysis (TEN).
Onset of erythema multiforme is usually sudden in an otherwise healthy individual. Red spots (macules or papules), or ridges (wheals), and sometimes blisters appear on the tops of the hands and forearms. Other areas of involvement may include the face, neck, palms, soles of feet, legs, and trunk. The lesions continue to erupt for two or three days. Some spots, especially on the hands and forearms, may evolve into concentric circles that resemble a target, with a grayish discoloration in the center. A crust may develop over the center. In about half of the cases, lesions may develop on the lips and the mucous membranes in the mouth. The skin lesions are usually distributed on both sides of the body. Itching can also occur.
Systemic symptoms vary, but malaise, pain in the joints (arthralgia), muscular stiffness and fever are frequent. Additional symptoms may include vision abnormalities; dry or bloodshot eyes; and eye pain, itching, or burning.
Attacks usually last two to four weeks, and may recur. Classic EM tends to recur two or three times a year for several years after its first appearance.
The cause of erythema multiforme is unknown, but it appears to be an allergic reaction that occurs in response to medications, infections, or illness. As noted above, it often appears in association with herpes simplex virus or with infectious organisms such as Mycoplasma pneumoniae.
In approximately half of the cases, it appears that the triggering agent is a medication. Drugs that have been associated with erythema multiforme include anticonvulsants, sulfonamides, nonsteroidal anti-inflammatory drugs, and other antibiotics.
Erythema multiforme is a rare disorder that affects slightly more males than females. It may begin at any age, but is most common in children and young adults.
Usually, the diagnosis can be made on the basis of the size, shape, color and distribution of the target lesions.
When a cause for erythema multiforme can be found, it should be treated, eliminated, or avoided (e.g. drugs or other substances to which the patient is allergic). Local treatment depends on the type of lesion.
Most people with classic erythema multiforme can be treated as outpatients with therapy, such as antihistamines, addressing their symptoms. Sometimes, no treatment is required.
For blisters and erosive lesions, intermittent moist compresses may be helpful. Over-the-counter antihistamines usually take care of whatever itching may be present. Infections of the lips and mouth usually can be managed with topical anesthetics but may, in some cases, require special care.
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