This article is based on an original article in Swedish which can be found here

BACKGROUND

Erythema multiforme (EM) is an uncommon hypersensitivity reaction and belongs to the group of vesiculobullous diseases that manifest in the oral cavity and can also involve skin and other mucous membranes. The condition often begins with a respiratory infection, such as sore throat, swollen lymph nodes, and mild fever or flu-like symptoms. Fatigue and headache may also occur. If only a localized area, such as the skin or the oral mucosa, is affected, it is referred to as EM minor, and if multiple areas such as both skin and mucous membranes (oral, nasal, genital) are involved, it is referred to as EM major. If only the oral cavity is involved, it is called oral EM. In about 70% of cases of EM, lesions in the oral mucosa appear with a clinical appearance ranging from erythema to blisters, ulcers, and erosions, and in the most severe cases, extensive epithelial necrosis. In cases of recurrent episodes, it is called recurrent erythema multiforme.

Stevens-Johnson syndrome (SJS) was previously classified as a more severe form of EM that, in addition to skin and mucous membrane involvement, also included conjunctivitis and balanitis/vaginitis. However, it is now considered a separate entity with many similarities to EM but is most often triggered by a drug reaction. The manifestations in the mucous membranes are similar, but the skin changes differ. Toxic Epidermal Necrolysis (TEN) is the most severe form of SJS, caused by a drug reaction in the skin that results in the necrosis and shedding of the entire thickness of the epidermis. Only a few cases of TEN have been described in the literature worldwide.

Another condition that should also be mentioned in this context is Rowell's syndrome, whose lesions have features of EM as well as lupus erythematosus with a specific immunological pattern containing antinuclear antibodies (ANA), positive anti-Ro/SSA or anti-La/SSB, and positive rheumatoid factor (RF).

This article will only present erythema multiforme (EM).

PREVALENCE

EM is a very rare condition affecting about 5–10 people per 1 million inhabitants in Sweden each year. The condition is extremely painful and often requires a multidisciplinary collaboration between dental care and healthcare. It usually affects essentially healthy men aged 20–40 years but can also occur in immunosuppressed patients, patients with HIV or systemic lupus erythematosus (SLE), and/or patients undergoing chemotherapy/radiation therapy.

CAUSES