Internal Medicine

P1: OXT/OZN/JDO P2: PSB

0521779407-E-01 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:10

546 Erythema Multiforme Major

■Initially, diffuse erythematous morbilliform eruption on face, trunk,

and then extremities

■Mimics exanthematous drug rash in early stages

■Rapid progression of skin findings

■Atypical targetoid lesions – individual lesions somewhat resemble a

target, with a central dusky region

■Purpuric quality to rash

■Flaccid or tense blisters may arise in involved areas

■Mucosal involvement key criteria for diagnosis – may precede or

parallel skin involvement

■Involvement typically of 2 or more mucosal surfaces (oral, ocular,

genital, gastrointestinal)

■Severe hemorrhagic crusting and erosions of lips

■Extensive erosions and pseudomembranes on buccal mucosa,

palate, other oral mucosa

■Erythema and erosions of ocular mucosa

■Toxic epidermal necrolysis (TEN) considered part of SJS spectrum;

more severe and extensive involvement (>30% skin involved)

tests

■Diagnosis usually made by typical clinical appearance of widespread

rash, mucosal erosions, and systemic symptoms

■In questionable cases, punch biopsy of involved area of skin – epi-

dermal necrosis with limited inflammation; degree varies with stage

of disease

■No test available to determine causative medication

Laboratory

■Rule out systemic involvement or systemic infection, and monitor

fluid and electrolyte status.

■CBC, electrolytes, albumin, liver function tests, renal function, uri-

nalysis

■Blood cultures, skin cultures, other, as clinically indicated

Imaging

■Only needed if internal organ involvement suspected – chest x-ray

differential diagnosis

■Drug rash

➣Presence of mucosal erosions, targetoid lesions, purpuric areas,

and blisters indicates progression to SJS.

■Erythema multiforme minor