A 3-day-old full-term male infant presents with a widespread rash of small erythematous macules, papules, and pustules on an erythematous base with a characteristic "flea-bitten" halo. The rash appeared 48 hours after birth and involves the face, trunk, and proximal extremities but spares the palms and soles. The mother is anxious about possible infection. A pustule is aspirated and examined under the microscope after Wright staining. The finding marked **D** in the diagram shows predominantly eosinophils in the pustule contents. Which of the following is the most appropriate next step in management?

Explanation

## Why "Reassurance and observation; the rash will resolve spontaneously without treatment or scarring" is right Erythema toxicum neonatorum (ETN) is a common benign neonatal rash affecting ~50% of full-term infants, appearing 24–72 hours after birth and peaking on day 3–4. The hallmark finding is small erythematous macules, papules, and pustules on a red base with a "flea-bitten" erythematous halo, characteristically sparing the palms and soles. The Wright stain finding marked **D** — predominantly eosinophils in the pustule contents — is pathognomonic for ETN and confirms the diagnosis. The etiology is unknown but likely represents a response to immune maturation or commensal flora colonization. Critically, ETN is self-limited and resolves spontaneously over 5–7 days without any treatment, without scarring, and without systemic complications. Management is purely supportive: parental reassurance and education. (Nelson 21e Ch 670) ## Why each distractor is wrong - **Initiate intravenous acyclovir and sepsis workup immediately**: This is the correct approach for neonatal herpes simplex virus (HSV) infection, which presents with clustered vesicles and carries risk of disseminated disease and sepsis. However, ETN pustules contain eosinophils, not multinucleated giant cells or viral inclusions. HSV is a critical differential diagnosis, but the Wright stain finding of eosinophils rules it out. - **Start topical or systemic antifungal therapy**: Neonatal candidiasis presents with diffuse pustules typically at birth and requires antifungal treatment. ETN appears 24–72 hours after birth and shows eosinophils, not yeast or pseudohyphae on stain. - **Administer intravenous antibiotics and obtain blood cultures**: This is appropriate for neonatal pustulosis caused by *Staphylococcus aureus*, which shows Gram-positive cocci on smear and requires sepsis workup and IV antibiotics. ETN pustules contain eosinophils and do not require antibiotics. **High-Yield:** Wright stain showing eosinophils in a neonatal pustular rash = erythema toxicum neonatorum = benign and self-resolving; reassure parents and observe. [cite: Nelson Textbook of Pediatrics, 21st Edition, Chapter 670]