Diagnosis: Eczema herpeticum
Eczema herpeticum is an overwhelming herpesvirus infection on skin already affected by atopic dermatitis. It is a dermatologic emergency—untreated infections may lead to complications, including herpes keratitis and disseminated herpes simplex virus (HSV) infections with visceral involvement. Mortality is 1%–9%,1 although before antiviral therapy it was as high as 75%.2
The rash begins as dome-shaped vesicles, which subsequently disappear and become punched-out excoriations, crusts, and erythematous plaques. The head, neck, and trunk are the most commonly affected areas. Systemic symptoms such as fever and malaise usually accompany the rash.
Causes of eczema herpeticum
The cause of eczema herpeticum is always HSV type I.3 The exact pathophysiology is unknown, but it is thought to involve HSV entering the skin when skin barrier function is compromised due to dermatitis. Defective cytokine secretion in the affected skin also plays an important role.3
The severity of preexisting eczema does not seem to dictate the severity of eczema herpeticum.4 Secondary bacterial skin infections are very common. A mixture of aerobic and anaerobic bacteria are commonly isolated, the most common being S aureus, Group A β-hemolytic Streptococcus, Pseudomonas, and Peptostreptococcus.6,7
Risks
It is not clear which patients with atopic dermatitis are more at risk for developing eczema herpeticum. High total serum immunoglobulin E (IgE) and early age of onset are 2 risk factors that have been identified.7,8
Some researchers have suggested that use of topical corticosteroids predisposes those with atopic dermatitis to develop eczema herpeticum, but larger studies do not support this.8 However, topical calcineurin inhibitors do seem to pose a higher risk and are thus contraindicated during an eczema herpeticum infection.9