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What is it about ?
Erythema multiforme is a reaction of the skin to a trigger. It is therefore not a skin disease. The triggering factor is usually an infection caused by a virus or bacteria, for example the Herpes simplex virus (which causes cold sores) or the Mycoplasma bacteria (which can cause an infection of the respiratory tract). But its exact cause often remains unknown. Certain medications can also trigger a severe variant of erythema multiforme.
How to recognize it?
Erythema multiforme most commonly affects young adults, but can occur at any age. In 80% of cases, the condition is not serious and the person does not feel sick. The red spots develop in a few days and do not move. They disappear spontaneously after a few weeks.
There are two forms: the minor form and the major form. In the minor form, the spots are symmetrical, measure 1-2 cm in diameter and are mainly localized on the limbs and face. They are characterized by their ‘target’ or ‘cockade’ appearance: a dark red or purple center (possibly with a small blister in the middle), surrounded by a slightly raised ring, lighter in color and well delimited by an edge. Red. In the major form, the rash is more pronounced, the blisters in the middle are larger, and the lining of the mouth may also be affected.
It is important to distinguish this relatively harmless rash from Stevens-Johnson syndrome and toxic epidermal necrolysis, which occur as a reaction to certain medications (anti-inflammatory drugs, antibiotics, and epilepsy medications). Stevens-Johnson syndrome is characterized by blue spots with blisters on the skin and on the mucous membranes, which are usually limited to 10% of the total area of the skin; in the end, the skin peels off at the lesions. In toxic epidermal necrolysis, which is a rare disease, the rash is more extensive and the skin peels off over more than 30% of the total body surface. Again, the mucous membranes are affected, with large lesions that resemble canker sores.
How is the diagnosis made?
The doctor will carefully inspect the lesions for a characteristic appearance (‘target’ or ‘cockade’). He will also check for lesions on the mucous membranes. He will examine whether an infection may be the cause of the skin reaction. Finally, he will check that it is not one of the dangerous variants of erythema multiforme (Stevens-Johnson syndrome or toxic epidermal necrolysis).
What can you do ?
Minor forms of erythema multiforme resolve spontaneously after 1 to 3 weeks. See a doctor if you have a marked rash, lesions on the mucous membranes, or if you feel ill.
What can your doctor do?
If a bacterial infection is causing the rash, it can be treated. Otherwise, the skin reaction usually goes away on its own. For the major form, the doctor often prescribes a course of cortisone for about three weeks. For the local treatment of lesions, a consultation is possibly organized with the skin specialist (dermatologist).
In the case of erythema multiforme associated with recurrent infections with the herpes simplex virus, treatment against the virus in question may be initiated.
If the doctor suspects Stevens-Johnson syndrome or toxic epidermal necrolysis, they will refer you directly to the emergency department.
Sources
Foreign clinical practice guidelines ” Erythema multiforme‘(2007), updated on 26.05.2017 and adapted to the Belgian context on 26.11.2019 – ebpracticenet
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