Eczema herpeticum is a disseminated viral infection characterised by fever and clusters of itchy blisters or punched-out erosions. It is most often seen as a complication of atopic dermatitis/eczema.
Eczema herpeticum is also known as Kaposi varicelliform eruption because it was initially described by Kaposi in 1887, who thought it resembled chickenpox/varicella.
What is the cause of eczema herpeticum?
Most cases of eczema herpeticum are due to Herpes simplex virus type 1 or 2.
Eczema herpeticum usually arises during a first episode of Herpes simplex infection (primary herpes). Signs appear 5 to 12 days after contact with an infected individual, who may or may not have visible cold sores.
Eczema herpeticum may also complicate recurrent herpes. However, repeated episodes of eczema herpeticum are unusual.
Eczema herpeticum can affect males and females of all ages but is more commonly seen in infants and children with atopic dermatitis. Atopics appear to have reduced immunity to herpes infection. The dermatitis can be mild to severe, active or inactive.
Eczema herpeticum can also occur when there are other reasons for breakdown of the skin barrier, including:
- Thermal burns
- Pemphigus vulgaris
- Darier disease
- Cutaneous T-cell lymphoma / mycosis fungoides
Other viruses may occasionally be responsible, such as coxsackievirus A16 (the cause of hand foot and mouth disease).
As smallpox has been eliminated, disseminated vaccinia as a consequence of smallpox vaccination is now very rare. It was reported to be very severe, with mortality of up to 50%.
Eczema herpeticum starts with clusters of itchy and/or painful blisters. It may affect any site but is most often seen on face and neck. Blisters can occur in normal skin or in sites actively or previously affected by atopic dermatitis or other skin disease. New patches form and spread over a period of 7 to 10 days and may rarely be widely disseminated throughout the body.
The patient is unwell, with fever and swollen local lymph nodes.
- The blisters are monomorphic, i.e. they all appear similar to each other.
- They may be filled with clear yellow fluid or thick purulent material.
- They are often blood-stained i.e., red, purple or black in colour.
- New blisters have central dimples (umbilication).
- They may weep or bleed.
- Older blisters crust over and form sores (erosions)
- Lesions heal over a period of 2-6 weeks.
- In severe cases where the skin has been destroyed by infection, small white scars may persist long term.
Severe eczema herpeticum may affect multiple organs, including the eyes, brain, lung, and liver. It can rarely be fatal.
Viral infection can be confirmed by viral swabs taken by scraping the base of a fresh blister. Several tests are available.
- Viral culture
- Direct fluorescent antibody stain
- PCR (Polymerase Chain Reaction) sequencing
- Tzank smear showing epithelial multinucleated giant cells and acantholysis (cell separation)
Bacterial swabs should also be taken for microscopy and culture as eczema herpeticum may resemble impetigo and it can be complicated by bacterial infection.
Eczema herpeticum is considered as one of the few dermatological emergencies. Prompt treatment with antiviral medication should eliminate the need for hospital admission.
Oral aciclovir 400 to 800 mg 5 times daily, or, if available, valaciclovir 1 g twice daily, for 10 to 14 days or until lesions heal. Intravenous aciclovir is prescribed if the patient is too sick to take tablets, or if the infection is deteriorating despite treatment.
Secondary bacterial skin infection is treated with systemic antibiotics.
Topical steroids are not generally recommended, but may be necessary to treat active atopic dermatitis.
Consult an ophthalmologist when eyelid or eye involvement is seen or suspected.