16
Erythema Multiforme, Stevens–Johnson Syndrome, and Toxic Epidermal Necrolysis
Erythema Multiforme
• Self-limited, but potentially recurrent, disease.
• Two forms: erythema multiforme (EM) major and EM minor (Table 16.1).
Table 16.1
Clinical features that distinguish erythema multiforme (EM) from Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and SJS–TEN overlap.
• Both forms have an abrupt onset of papular ‘target’ lesions that favor acrofacial sites.
• Two types of target lesions: (1) typical targets, with at least three different zones; (2) atypical papular targets, with only two different zones and/or a poorly defined border (Fig. 16.1).
Fig. 16.1 Phenotypic variety in lesions of erythema multiforme (EM). A Edematous/urticarial. B Urticarial with central crusting. C Erythematous plaques with dusky centers; coalescence of the lesions leads to a well-defined polycyclic outline. D, E Typical (classic) target lesions on the palms and dorsal hand, with three zones of color change (‘bull’s eye’); note the central vesicles in (D). F Atypical papular target lesions on the upper forehead mixed with more typical target lesions on the lower forehead. G Isomorphic response. H Mucosal involvement in EM major. Typical target lesions are seen as well as serous crusting of the vermilion lips and eyelid margin. At the margin of the serous crusting of the lip, there are two zones of color with a polycyclic outline. A, D, G, Courtesy, William Weston, MD.
• Preceding HSV infection is most common precipitating factor; less often other preceding infections, in particular Mycoplasma pneumoniae (Table 16.2; Fig. 16.2); rarely drug exposure.
Table 16.2
Precipitating factors in erythema multiforme.
This is a non-exhaustive list based primarily on case reports and small series of cases. The most common causes are in bold.
Fig. 16.2 Mycoplasma pneumoniae-associated mucositis (MPAM). MPAM is an extrapulmonary manifestation of M. pneumoniae infection that falls along the spectrum of EM major or SJS. In MPAM, there may be isolated mucosal lesions (e.g. ocular, oral, and urogenital) or a combination of mucosal and minimal skin lesions. Note the hemorrhagic and serous crusting of the vermilion lips (A) in this 12-year-old male with M. pneumoniae infection who presented with isolated oral and genital (B) lesions. A, B, Courtesy, Julie V. Schaffer, MD.
• Diagnosis based on clinicopathologic correlation and not solely histopathologic findings.
• EM is a distinct disorder from Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) (see Table 16.1).
• EM does not progress to TEN.
• DDx: giant urticaria (Fig. 16.3; Table 16.3), morbilliform drug reaction (Fig. 16.4), multiple fixed drug eruption (FDE), acute hemorrhagic edema of infancy, Kawasaki disease, small vessel vasculitis, Rowell’s syndrome, GVHD, polymorphic light eruption (PMLE).
