Erythema multiforme

What is Erythema multiforme ?

Erythema multiforme is a disorder that leads to eruption of lesions which in turn is due to reaction of hyper sensitive skin. Generally it is caused by herpes simplex virus infection. It can be acute, self limiting and it may develop in mucous membranes. Normally it fades off automatically without causing any complications.

There are two types of Erythema multiforme, namely, major and minor. Erythema multiforme is different from Toxic epidermal Necrolysis and Stevens Johnson syndrome. It can affect any one without exception, but it normally tends to affect those who are in the age group of 20 to 40, and more particularly the male gender.

Symptoms of Erythema multiforme

Normally, Erythema multiforme minor does not show prodromal symptoms; whereas the Erythema multiforme major shows mild signs of fever, chills, weakness across the body, and joint pains.

Skin lesions:

Within a period of 24 hrs from infection, the lesions occur in few or in many numbers. These lesions occur first over the rear portions of hands, and/or on tops of feet. Afterwards the lesions spread to other areas such as, face, trunk, neck, elbows and knees. The lesions may cause mild itching and burning sensation.
In the beginning period the lesions remain isolated with flat and round shape, red or pink in color. Later it may get enlarged and develop into patches of plaques. In course of time it may develop into plaque patches with dark center and grow to form crusting and blistering.

In general the lesions of Erythema multiforme have a round shape and sharp margins with three concentric color formations such as:

Blister crust with dark red center
The next ring around is light pinkish with swelling due to the filling of fluids in it.
The third ring and the final ring, has bright red appearance.

The lesions may have two zones with no clear borders.

To have an idea about the stage of lesion, the whole body is required to be examined. The rash sites may not have any swelling. However, in Erythema multiforme major cases, the lips may show the swelling.

Mucous membrane involvement:

In Erythema multiforme minor cases, the mucous membrane involvement is almost absent or mild. Increased redness of cheek and the lips are the signs of mucosal changes. In few cases the blisters develop, break and form ulcers.
The condition of mucosal lesions comes up, after few days of contracting skin rash.

The mucous membranes shown below are affected by the EM major:

Inside cheeks, lips and tongue
The palate, gums and the floor of the mouth also get affected in rare cases.
The genitals and the anus
Gastrointestinal tract
The trachea/bronchi
The eyes

Normally the mucosal lesions have swelling and painful blisters, superficial ulcers covered by whitish pseudo membrane. The hemorrhagic crusts in swollen lips may cause difficulty in speaking, drinking and swallowing.

Mycoplasma pneumonia attacks only the mucous membranes and it may need hospitalization, if it is severe.

Erythema multiforme can recur and can repeat for many years. It is believed that the HSV-1 infection is the primary reason for the recurrence.

Causes of Erythema multiforme

Infections: Majority of Erythema multiforme cases are caused by infections.

Infection with the Herpes simplex virus is the major cause of Erythema multiforme. Normally herpes labialis and in few occasions the genital herpes induce Erythema multiforme. Within 3 to 14 days from infection, the eruptions develop.
Another common cause for Erythema multiforme is mycoplasma pneumonia, caused by mycoplasma pnuemoniae.

Different types of virus infections causing Erythema multiforme are:

Viruses of adeno, hepatitis, parapox, HIV, herpes varicella zoster, and cytomegalo
Viral vaccines
Dermatophyte fungal infection

Drugs: Hardly about ten percent of the cases of Erythema multiforme are caused by the drug reactions.

It has been reported that NSAIDs, sulphonamides, barbiturates, phenothiazines, penicillin and anticonvulsant drugs also cause Erythema multiforme.