Not all that vesicles is herpes.

BACKGROUND: Eczema coxsackium (EC) can manifest in patients with underlying atopic dermatitis (AD) as a diffuse vesicular rash in a febrile child. The presentation overlaps clinically with the feared diagnosis of eczema herpeticum (EH), which makes differentiating between the conditions very important.

CASE PRESENTATION: A 6-month-old girl with known AD presented with fever and rapidly spreading vesicular rash. The patient had multiple exposures including a new antibiotic prescription, introduction of new foods, 6-month vaccinations and a sick contact. She was treated empirically with acyclovir for EH until herpes simplex virus (HSV) polymerase chain reaction (PCR) returned negative and enterovirus PCR returned positive. Once the diagnosis of EC was confirmed, antiviral therapy was discontinued and she was treated successfully with supportive measures without sequelae.

CONCLUSIONS: Differentiating EC from EH is important clinically as EC is self-limiting and resolves spontaneously whereas EH may cause severe complications if not treated early. While morphology alone cannot reliably distinguish between the conditions, clinical suspicion based on history can prompt proper testing and improve patient outcomes.