Erythema multiforme

Erythema multiforme is a hypersensitivity reaction that is most commonly triggered by infections. It may be divided into minor and major forms.

Previously it was thought that Stevens-Johnson syndrome (SJS) was a severe form of erythema multiforme. They are now however considered as separate entities.

Features

target lesions
initially seen on the back of the hands / feet before spreading to the torso
upper limbs are more commonly affected than the lower limbs
pruritus is occasionally seen and is usually mild

Causes

viruses: herpes simplex virus (the most common cause), Orf*
idiopathic
bacteria: Mycoplasma, Streptococcus
drugs: penicillin, sulphonamides, carbamazepine, allopurinol, NSAIDs, oral contraceptive pill, nevirapine
connective tissue disease e.g. Systemic lupus erythematosus
sarcoidosis
malignancy

Erythema multiforme

Erythema multiforme on the right side of the neck. In this case, developed after the onset of herpes labailis

Erythema multiforme - giant target lesions on her forearms

Erythema multiforme

Erythema multiforme major

The more severe form, erythema multiforme major is associated with mucosal involvement.

This image shows the ventral and lateral surfaces of the tongue with multiple irregular, erythematous patches and areas of epithelial sloughing and superficial ulceration, consistent with mucosal erosions. The lesions have a geographic and well-demarcated appearance, and are surrounded by erythematous mucosa, indicating active inflammation. These findings are characteristic of erythema multiforme major, which typically involves painful mucosal erosions (oral, ocular, or genital) in conjunction with targetoid skin lesions. Erythema multiforme major is often precipitated by HSV infection or medications and requires prompt recognition.

Example of mucosal involvement in erythema multiforme major

*Orf is a skin disease of sheep and goats caused by a parapox virus

+PassMedicine Notes

Erythema multiforme is a hypersensitivity reaction that is most commonly triggered by infections. It may be divided into minor and major forms.

Previously it was thought that Stevens-Johnson syndrome (SJS) was a severe form of erythema multiforme. They are now however considered as separate entities.

Features

target lesions
initially seen on the back of the hands / feet before spreading to the torso
upper limbs are more commonly affected than the lower limbs
pruritus is occasionally seen and is usually mild

Causes

viruses: herpes simplex virus (the most common cause), Orf*
idiopathic
bacteria: Mycoplasma, Streptococcus
drugs: penicillin, sulphonamides, carbamazepine, allopurinol, NSAIDs, oral contraceptive pill, nevirapine
connective tissue disease e.g. Systemic lupus erythematosus
sarcoidosis
malignancy