Erythema multiforme

Management Strategy

In 30%–50% of cases the etiology of EM is unknown. The most commonly recognized precipitant is HSV infection; both types I and II HSV-specific DNA has been isolated from lesional tissue in 60%–70% of cases. HSV particles are found in the circulating precursors of epidermal Langerhans cells. A variety of other viral infections (orf, varicella zoster virus [VZV], Epstein–Barr virus [EBV], cytomegalovirus [CMV], human immunodeficiency virus [HIV], hepatitis B vaccination), bacterial infections (mainly Mycoplasma pneumoniae but also tularemia), and fungal infections (predominantly histoplasmosis) have been implicated. An extensive list of drugs has been reported to trigger EM, but most cases, if not all, are the result of confusion with Stevens–Johnson syndrome. Rare cases may be attributed to contact allergy.

Acute episodes of EM need only symptomatic treatment in most cases. Recurrent EM, which may severely affect quality of life, has a well-recognized preventive treatment in case of HSV infection but may be highly recalcitrant when no cause is identified. A persistent continuous variety of EM has been reported with antidesmoplakin antibodies, which do not testify pemphigus.

There are no double-blind or open trials of treatments for acute episodes of EM. Most cases, particularly EM minor, run a self-limiting course. Symptomatic measures include oral antihistamines and mild-to-moderate-potency to reduce pruritus. Underlying conditions, mainly Mycoplasma pneumoniae infection, should be treated. Recurrent EM (>6 attacks per year) may respond to long-term anti-HSV drugs . In resistant cases a variety of other therapies can be helpful (see later).

Mucosal manifestations of EM major are a source of morbidity. The most common sites affected are the buccal mucosa and lips. Symptomatic measures include mouthwashes, a soft diet , topical anesthetics , and topical corticosteroids (e.g., 0.1% triamcinolone acetonide paste). Budesonide or beclomethasone inhalers (one puff three to four times daily) provide an alternative method of delivering local corticosteroid to the inflamed mucosal surfaces. Short courses of high-dose oral prednisolone may be needed for severe oral disease. Strict eye care to reduce secondary infection and scarring includes saline washes for removal of crusts, local antibiotics , and frequent debridement of tarsal and bulbar conjunctival adherences .

EM is a clinical diagnosis. Histology, with direct immunofluorescence, can be useful in atypical cases to exclude other bullous diseases that present with oral manifestations, such as pemphigus vulgaris or cicatricial pemphigoid.

Investigations directed at determining the underlying trigger factors include culture or serologic testing for HSV or other infections, especially M. pneumoniae, as indicated by clinical findings.