Erythema Multiforme (EM)

Question 1

Main patient population that gets Erythema multiforme and in what seasons?

Answer 1

• young adults (M=F) in spring and fall

Question 2

____ % of EM cases are caused by infection.

Answer 2

• 90%

Question 3

What is the most common trigger of erythema multiforme?

Answer 3

• HSV (HSV1>HSV2)

Question 4

Which HSV more commonly causes EM?

Answer 4

• HSV 1 > 2

Question 5

Most common cause of EM minor>

Answer 5

• Herpes virus

Question 6

Herpes labials outbreak usually precedes EM by how long?

Answer 6

• 1-3 weeks

Question 7

Most common cause of EM major?

Answer 7

• Mycoplasma pneumoniae!! - will see severe mucous membrane involvement, atypical papular target lesions

Question 8

EM caused by Mycoplasma pneumoniae will present with:

Answer 8

• severe mucous membrane involvement, atypical papular target lesions

Question 9

EM can be caused by histoplasmosis capsulate, and can have concomitant _____

Answer 9

• erythema nodosum

Question 10

____% of EM is drug induced.

Answer 10

• 10%

Question 11

Drugs that can cause erythema multiforme?

Answer 11

• NSAIDS, antibiotics, sulfonamides, anti epileptics, TNF-alpha inhibitors

Question 12

EM clinical presentation

Answer 12

• Abrupt- onset of erythematous macules–>papules and targetoid lesions affecting the extremities and face

Question 13

Classic targetoid lesions of EM

Answer 13

• have three zones:
  1) dusky center that may have vesiculation or necrosis
  2) pale ring surrounding dusky center
  3) Outer macular erythematous ring

Question 14

Erythema multiforme lesions favor which body parts?

Answer 14

Face and distal extremities

Question 15

Targetoid lesions that are papular or elevated are considered ____, whereas those that are nonpalpable or macular are considered ______

Answer 15

• elevated and papular= typical
• macular/nonpalpable= atypical

Note: Macular atypical targets are seen in SJS/TEN, but not EM

Question 16

What type of targetoid lesios do you see in EM, typical or atypical?

Answer 16

typical!

- atypical (macular) are seen in SJS/TEN.

Question 17

Presence of _____ target lesions and ____ distribution allow for reliable distinction of EM from SJS/TEN

Answer 17

• Elevated/papular target lesions and acrofacial distribution are EM, not SJS/TEN

Question 18

Can either EM minor or major progress to SJS/TEN?

Answer 18

nope

Question 19

Difference between EM minor and major?

Answer 19

EM Minor:

• NO systemic symptoms (e.g. Fever, arthralgias)
• Minimal mucosal involvement

EM Major:

• Systemic symptoms
• More severe mucosal involvement (e.g. Erosions of

buccal mucosa and lips)

Question 20

Three main differences between EM and SJS?

Answer 20

1) EM = papular targetoid lesions vs SJS = +/- macular targetoid lesions
2) EM favors hands, extremities, and face vs SJS/TEN which relatively spares distal extremities
3) EM has specific associations (like HSV or mycoplasma pneumonia infections)

Question 21

EM+history of subacute or discoid lupus=

Question 22

Histology of Erythema multiforme will show:

Answer 22

In order of picture:

• Dead reds (dead keratinocytes)
• spongiosis
• Epidermal lymphocytes
• Superficial infiltrate w/ lymphocytes & histocytes

Question 23

_____ % of EM lesions will have detectable HSV DNA by PCR in the target lesions?

Answer 23

• 80%

Question 24

Treatment of EM?

Answer 24

• Symptomatic Tx as it is self limiting after two weeks
• for pruritis= antihistamines/TCS
• painful oral lesions= magic mouthwash
• if 2/2 recurrent HSV: HSV PPx with acylcovir 400mg daily or valacyclovir 500mg daily

Note: in severe cases can consider systemic steroids or immunosuppressants

Question 25

Prognosis/clinical course of erythema multiforme for mild cases? severe?

Answer 25

• mild-moderate disease will self resolve without sequelae in 2 weeks
• EM major with severe mucosal involvment can persist up to 6 weeks and maybe a/w ocular complications

Question 26

Timeline for erythema multiforme rash:

Answer 26

• acute onset of lesions over 24hrs—> eruption fully developed by 72 hours–> self-resolves without sequelae in 2 weeks (unless EM major with severe mucosal involvement which can take 6 weeks to complete)