A 1-week-old infant has a papular rash with clustered lesions, some vesicular, and is otherwise healthy. What is the most likely diagnosis?

A 1-week-old infant has a papular rash with clustered lesions, some vesicular, and is otherwise healthy. What is the most likely diagnosis?

• A. Neonatal pustular melanosis
• B. Millia
• C. Erythema toxicum
• D. Neonatal acne

Answer: (C)

Erythema toxicum neonatorum is the pattern to recognize here. It’s a very common, benign rash in newborns that typically appears within the first few days of life and can persist for up to a couple of weeks. The hallmark is small vesiculopustular lesions grouped on an erythematous base, often on the trunk and proximal limbs, while the infant otherwise looks well and behaves normally. This fits a 1-week-old infant with clustered papules and some vesicles and no systemic illness, for which no treatment is needed beyond observation. Neonatal pustular melanosis usually presents with pustules at birth that rupture and leave pigmented macules, often lasting longer and sometimes seen more in darker skin. Millia are tiny white keratin-filled cysts on the face that aren’t vesicular or clustered in the same way. Neonatal acne tends to appear later (usually after 2–4 weeks) and involves comedones and inflammatory papules/pustules on the face, not the typical vesiculopustular eruption seen here.

Erythema toxicum neonatorum is the pattern to recognize here. It’s a very common, benign rash in newborns that typically appears within the first few days of life and can persist for up to a couple of weeks. The hallmark is small vesiculopustular lesions grouped on an erythematous base, often on the trunk and proximal limbs, while the infant otherwise looks well and behaves normally. This fits a 1-week-old infant with clustered papules and some vesicles and no systemic illness, for which no treatment is needed beyond observation.

Neonatal pustular melanosis usually presents with pustules at birth that rupture and leave pigmented macules, often lasting longer and sometimes seen more in darker skin. Millia are tiny white keratin-filled cysts on the face that aren’t vesicular or clustered in the same way. Neonatal acne tends to appear later (usually after 2–4 weeks) and involves comedones and inflammatory papules/pustules on the face, not the typical vesiculopustular eruption seen here.