Erythema Multiforme

Question 1

What is erythema multiforme (EM)?

Answer 1

A hypersensitivity reaction characterized by target-like lesions on the skin, often triggered by infections or medications.

Question 2

What are the two forms of erythema multiforme?

Answer 2

Erythema multiforme minor: Limited to the skin with minimal or no mucosal involvement.

Erythema multiforme major: Involves mucous membranes in addition to skin lesions.

Question 3

Who is most commonly affected by EM?

Answer 3

Young adults aged 20–40 years, but it can occur at any age.

Question 4

What is the most common trigger of erythema multiforme?

Answer 4

Infections, particularly herpes simplex virus (HSV).

Question 5

What other infections are associated with EM?

Answer 5

Mycoplasma pneumoniae.

Epstein-Barr virus (EBV).

Cytomegalovirus (CMV).

Fungal or parasitic infections (rare).

Question 6

What medications are known to trigger EM?

Answer 6

NSAIDs.

Sulfonamides.

Anticonvulsants (e.g., phenytoin, carbamazepine).

Antibiotics (e.g., penicillins).

Question 7

What causes erythema multiforme?

Answer 7

It is a type IV hypersensitivity reaction mediated by cytotoxic T-cells, leading to keratinocyte apoptosis and inflammation.

Question 8

How does HSV trigger EM?

Answer 8

Viral antigens stimulate an immune response, resulting in T-cell-mediated damage to keratinocytes.

Question 9

What are the hallmark skin lesions of erythema multiforme?

Answer 9

Target lesions: Round, erythematous macules or papules with three concentric zones (central dusky area, pale ring, outer red ring).

Lesions are often symmetrical and affect the acral areas (hands, feet).

Question 10

What mucous membranes are commonly involved in EM major?

Answer 10

Oral mucosa.

Conjunctiva.

Genitals.

Question 11

What systemic symptoms may accompany EM?

Answer 11

Fever, malaise, and arthralgia, especially in EM major.

Question 12

Does EM cause pruritus or pain?

Answer 12

Lesions may be painful but are usually non-pruritic.

Question 13

How is erythema multiforme diagnosed?

Answer 13

Clinical diagnosis based on characteristic target lesions and history of triggers.

Skin biopsy may be used to confirm diagnosis in atypical cases.

Question 14

What are the histopathological findings in EM?

Answer 14

Epidermal necrosis and subepidermal blistering.

Lymphocytic infiltrate at the dermoepidermal junction.

Apoptotic keratinocytes.

Question 15

What conditions should be considered in the differential diagnosis of EM?

Answer 15

Stevens-Johnson Syndrome (SJS) or toxic epidermal necrolysis (TEN).

Urticaria.

Erythema migrans (Lyme disease).

Fixed drug eruption.

Acute cutaneous lupus erythematosus.

Question 16

What is the primary treatment for erythema multiforme minor?

Answer 16

Symptomatic relief:

Topical corticosteroids for inflammation.

Antihistamines for itching.

Analgesics for pain.

Question 17

How is HSV-associated EM managed?

Answer 17

Antiviral therapy (e.g., acyclovir, valacyclovir) to suppress HSV reactivation.

Long-term antiviral prophylaxis for recurrent EM.

Question 18

What is the treatment for erythema multiforme major?

Answer 18

Systemic corticosteroids (controversial, used in severe cases).

Supportive care for mucosal involvement (e.g., oral rinses, lubricating eye drops).

Treatment of underlying infection or removal of triggering medication.

Question 19

What is the typical duration of erythema multiforme?

Answer 19

EM minor resolves within 1–2 weeks, while EM major may take longer (up to 6 weeks).

Question 20

How is EM major managed?

Answer 20

Systemic corticosteroids: Prednisone (0.5–1 mg/kg/day) for short-term use in severe inflammation.

Mucosal care:
- Oral antiseptic rinses (e.g., chlorhexidine).
- Topical anesthetics (e.g., viscous lidocaine) for pain relief in oral lesions.
- Ophthalmologic lubricants or corticosteroid drops for eye involvement.

Treat underlying infection (e.g., antibiotics for Mycoplasma pneumoniae).

Question 21

Are corticosteroids always recommended in EM major?

Answer 21

The use of corticosteroids is controversial. They may be considered in severe cases but should be avoided in infectious triggers without concurrent antimicrobial therapy.

Question 22

What immunosuppressive agents are used in refractory or recurrent EM?

Answer 22

Dapsone.

Azathioprine.

Mycophenolate mofetil.

Hydroxychloroquine (in cases with a lupus overlap).

Question 23

How does erythema multiforme differ from Stevens-Johnson Syndrome (SJS)?

Answer 23

EM:
* Target lesions with concentric zones.
* Acral distribution.
* Mild mucosal involvement.
* Less systemic involvement.

SJS:
* Widespread epidermal detachment and necrosis.
* Prominent mucosal involvement (oral, ocular, genital).
* Significant systemic symptoms (fever, malaise).

Question 24

How does erythema multiforme differ from Toxic Epidermal Necrolysis (TEN)?

Answer 24

EM:
* Limited epidermal involvement (<10% BSA).
* Typical target lesions.
* Milder systemic symptoms.

TEN:
* Extensive epidermal detachment (>30% BSA).
* Full-thickness necrosis and severe systemic involvement.

Question 25

How does erythema multiforme differ from Urticaria?

Answer 25

EM:
* Fixed target lesions lasting several days.
* Painful, non-pruritic.

Urticaria:
* Transient wheals lasting <24 hours.
* Intensely pruritic.

Question 26

How does erythema multiforme differ from Drug Rash with Eosinophilia and Systemic Symptoms (DRESS)?

Answer 26

EM:
- Target lesions, limited systemic involvement.

DRESS:
- Morbilliform or widespread rash.
- Associated with eosinophilia, lymphadenopathy, and organ involvement (liver, kidney).

Question 27

How does erythema migrans (Lyme disease) differ from EM?

Answer 27

Erythema migrans: A single, expanding, ring-like lesion with central clearing, no mucosal involvement, associated with
Lyme disease.

EM: Multiple target lesions with distinct zones, often involving mucosa.

Question 28

What key features differentiate acute cutaneous lupus erythematosus from EM?

Answer 28

Lupus erythematosus: Photosensitivity, discoid lesions, positive ANA, and systemic symptoms like arthritis.

EM: Target lesions, triggered by infections or drugs, no systemic lupus markers.