Eczema herpeticum, previously known as Kaposi varicelliform eruption, is a viral skin infection caused by herpes simplex virus (HSV) and varicella zoster virus (VZV). It is a dermatological emergency, as it indicates a disseminated viral infection in the patient.
Pathophysiology
The most common causative agent is HSV-1 & HSV-2. It is usually seen in patients who have these viruses in addition to having atopic dermatitis/eczema, as this facilitates the entry of the virus through the skin barrier and creating an infection. The compromised skin barrier that occurs allows the virus to enter through micro-abrasions, initiating infection in keratinocytes and promoting viral replication. The impaired innate immune responses in atopic dermatitis, including reduced antimicrobial peptides and weakened natural killer cell activity, contribute to uncontrolled viral replication. This viral invasion triggers an intense inflammatory response characterized by the release of cytokines, leading to the formation of erosions and vesicles. The infection can rapidly spread to multiple skin areas and mucous membranes, potentially disseminating through the bloodstream, causing systemic symptoms, and giving rise to severe complications such as bacterial superinfections, sepsis, and disseminated intravascular coagulation.
⚠️ Risk factor
- Severe eczema
- Atopy
- History of Staphylococcus aureus and molluscum contagiosum infection
😷 Presentation
It normally occurs when the patient is first infected with HSV. Signs appear 5–12 days after contact with an infected individual, who may or may not have visible cold sores.
A typical presentation is a patient who suffers with eczema that has developed:
- Widespread, painful, vesicular rash
- Systemic symptoms such as:
- Fever
- Lethargy
- Irritability
- Reduced oral intake
- Lymphadenopathy
The lesions that are present all appear the same. They may be filled clear yellow fluid or thick purulent material. They are often blood-stained and may weep. Fresh vesicles may have a central umbilication. Old blisters crust over and form erosions. The lesions ultimately heal in 2-6 weeks and white scars may persist. Secondary bacterial infection with staphylococci or streptococci may lead impetigo or cellulitis.
🔍 Investigations
⭐️ Eczema herpeticum can be diagnosed clinically when a patient with known atopic dermatitis presents with an acute eruption of painful, monomorphic clustered vesicles associated with fever and malaise.
- 🏆 Viral infection can be confirmed by viral swabs taken by scraping the base of a fresh blister, although we do not need to wait for the results to start treatment.
- Bacterial swabs should also be taken for microscopy and culture as eczema herpeticum may resemble impetigo and it can be complicated by secondary bacterial infection.
Other laboratory tests that can be considered:
- Direct fluorescent antibody stain
- PCR sequencing
- 🏆 Tzanck smear - showing epithelial multinucleated giant cells and acantholysis (cell separation).
🧰 Management
Prompt treatment with antiviral medication should eliminate the need for hospital admission.
- Antivirals
- Antivirals are often given concomitantly with antibiotics as concomitant bacterial infection is common and difficult to exclude clinically.
- Previously, topical steroids have not been recommended, but recent evidence shows they are safe & helpful to manage active atopic dermatitis.
🥇 Oral aciclovir - 400–800 mg 5x daily for mild-to-moderate cases.
🥇 IV aciclovir for more severe cases
🚨 Complications
- Children with eczema herpeticum can be very unwell. When not treated adequately it can be a life threatening condition, particularly in patients that are immunocompromised.
- Bacterial superinfection can occur, leading to a more severe illness.