Published on 19/03/2015 by admin
Filed under Dermatology
Last modified 19/03/2015
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Jean Revuz
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Erythema multiforme (EM) is a distinct cutaneous reaction pattern to a variety of stimuli, predominantly herpes simplex virus (HSV) infection. It usually runs a self-limiting course but has a tendency to recur. It is defined by the presence of ‘typical’ three-zone target lesions, with a predominantly acral distribution. The presence of mucosal involvement at more than one site distinguishes EM major from EM minor. A specific variant has mucosal lesions only, without skin involvement. EM major can be distinguished from Stevens–Johnson syndrome which lacks typical target-like lesions and acral location but, instead, irregular macule or atypical targets and a truncal location. EM is frequently misdiagnosed in cases of urticaria and more rarely in cases of cutaneous lupus, vasculitis, erythema annulare, and drug eruption.
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, VZV, EBV, CMV, HIV), bacterial infections (mainly Mycoplasma pneumoniae), and fungal infections (mainly histoplasmosis), have been implicated. An extensive list of drugs have been reported to trigger EM but most cases if not all are the result of a confusion with Stevens-Johnson syndrome. Rare cases are 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.
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 topical corticosteroids to reduce pruritus. Underlying conditions, mainly Mycoplasma pneumoniae infection, should be treated. Recurrent EM (>6 attacks per year) may respond to long-term acyclovir. In acyclovir-resistant cases a variety of other therapies can be helpful (see below).
Mucosal manifestations of EM are a source of morbidity and occur in up to 70% of cases. The commonest sites affected are the buccal mucosa and lips. Symptomatic measures include mouthwashes, a soft diet, topical anesthetics (lidocaine gel, benzocaine lozenges or 0.15% benzydamine hydrochloride), 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.
Histology/immunofluorescence
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 serological testing for HSV or other infections, especially Mycoplasma pneumoniae, as indicated by clinical findings.
Schofield JK, Tatnall FM, Leigh IM. Br J Dermatol 1993; 128: 542–5.
A review of 65 patients with recurrent EM: 71% had episodes triggered by HSV infection. In one patient, EM was related to the menstrual cycle and could be precipitated by intramuscular progesterone injection. Treatment with standard doses of acyclovir for HSV was relatively disappointing; continuous acyclovir 400 mg twice daily for six months was more effective, with remission in some responders. Some patients responded to dapsone, antimalarials, azathioprine, and human immunoglobulin.
Tatnall FM, Schofield JK, Leigh IM. Br J Dermatol 1995; 132: 267–70.
Acyclovir 400 mg twice daily for 6 months suppressed EM in seven of 11 patients (including one with apparently idiopathic EM). Two patients went into complete remission.
A therapeutic trial of acyclovir is justified even when clinical evidence of HSV is lacking. Acyclovir 400 mg twice daily can be administered for 6 months to 2 years because it has a good long-term safety profile. It is ineffective in an acute episode once the herpetic lesion or EM eruption has developed.
Kerob D, Assier-Bonnet H, Esnault-Gelly P, Blanc F, Saiag P. Arch Dermatol 1998; 134: 876–7.
A reduced response to acyclovir may be due to the low oral bioavailability of the drug, and one of the second-generation antivirals, such as valacyclovir (500 mg daily) or famciclovir (250 mg twice daily) may need to be substituted.
Treatment of Skin Disease Comprehensive Therapeutic Strategies 4e
Acyclovir
