“Erythema multiforme (EM) is an acute, often recurrent, inflammatory condition. While it is associated with many different causes such as drugs, infections, and physical agents, it is most commonly associated with acute upper respiratory infections, herpes simplex virus, and Mycoplasma pneumoniae.
EM typically occurs in persons 20–40 years of age, with urticarial papules or the classic bull’s-eye or target lesions. The distribution is primarily on the hands (both the dorsi and palms), soles, and extensor aspects of the arms and legs. Lesions may also occur on mucosal surfaces, but in typical EM these are milder than in the more severe Stevens-Johnson syndrome, which is more commonly associated with drug exposure than with infectious agents.
The lesions of EM are usually pruritic, but not universally so. They evolve to the typical target forms over 24–48 hr. The central area is often dusky and may be superficially necrotic or vesicular. Partial target lesions may resemble urticaria. The lesions usually heal without scarring over a 10- to 14-day period.
An id reaction is a papulovesicular eruption, classically on the sides of fingers, that occurs in response to an intense inflammatory process such as a fungal infection or acute dermatitis in another anatomic area of the body. When that condition resolves, so does the id reaction.
Discoid lupus lesions are irregular but roughly round in shape, sharply demarcated, and most commonly found on the face or scalp. They usually develop an adherent thick scale. The duration may be months or years.
Granuloma annulare manifests as a ring of firm, flesh-colored or red papules with a more prominent outer ring forming due to central involution. These lesions may last for months to years. The distribution is usually on the dorsolateral aspect of the hands or feet.
Pyoderma gangrenosum begins as a tender papule, usually on the lower leg, and evolves to a painful, necrotic, inflammatory lesion that gradually enlarges up to 10 cm. It usually is a manifestation of an underlying systemic inflammatory condition such as inflammatory bowel disease. The lesions last for months to years and heal with scarring.”ABFM
