A 48-hour-old term male newborn is evaluated in the nursery for a new skin eruption. The i… — USMLE Step 2 CK

A $48$ -hour-old term male newborn is evaluated in the nursery for a new skin eruption. The infant was delivered via uncomplicated spontaneous vaginal delivery at $39$ weeks gestation to a $28$ -year-old primigravida. Maternal prenatal laboratory studies were unremarkable, and maternal Group B Streptococcus screening was negative. The newborn has been breastfeeding vigorously and has had normal bowel and bladder output. Vital signs show a temperature of $37.0$ °C ( $98.6$ °F), a heart rate of $135$ /min, and a respiratory rate of $42$ /min. Physical examination reveals a well-appearing, alert infant. His skin exhibits a scattered rash on the chest, abdomen, and proximal extremities consisting of $1$ - to $3$ -cm erythematous macules, many of which contain a central $1$ - to $2$ -mm yellow-white pustule. The palms, soles, and mucous membranes are entirely clear. Which of the following is the most appropriate next step in management?

A
Blood, urine, and cerebrospinal fluid cultures followed by empiric ampicillin and gentamicin
B
Application of topical mupirocin to the lesions
Reassurance and continued routine newborn careAnswer
D
Intravenous acyclovir and viral surface swabs
E
Microscopic examination of a pustule scraping with potassium hydroxide

Answer

Reassurance and continued routine newborn care

The correct answer is reassurance and continued routine newborn care because the clinical presentation is classic for erythema toxicum neonatorum (ETN). ETN is a benign, self-limited rash that typically appears in the first few days of life in full-term neonates. It is characterized by erythematous macules and papules that often develop central pustules containing eosinophils. The rash notably spares the palms and soles. Because the infant is asymptomatic, feeding well, and has normal vital signs, no diagnostic testing or medical intervention is required. The rash will spontaneously fade and resolve over the subsequent days.

Step-by-Step Solution

Analyze the patient's age and the morphological characteristics of the skin eruption.

The patient is a

48

-hour-old, well-appearing neonate with a rash consisting of scattered erythematous macules and central pustules on the trunk and proximal extremities, which uniquely spares the palms and soles.

Identifying the timing, morphology, and distribution of the rash is essential for distinguishing between various neonatal skin conditions.

Differentiate benign physiologic conditions from pathological neonatal eruptions.

The absence of systemic symptoms (such as fever or lethargy), the sparing of the mucous membranes, palms, and soles, and the characteristic 'flea-bitten' appearance strongly point to Erythema Toxicum Neonatorum (ETN) rather than infectious etiologies like neonatal HSV or sepsis.

Distinguishing a benign, self-limited condition from a life-threatening infectious disease dictates whether a clinical workup is necessary.

Determine the appropriate management for Erythema Toxicum Neonatorum.

Because ETN is a benign and transient condition that spontaneously resolves within a week, no diagnostic testing or pharmacologic treatment is indicated.

Interventions like empiric antibiotics or antivirals carry unnecessary risks, violate antimicrobial stewardship principles, and provide no benefit for physiologic rashes.

Key Concept

Erythema toxicum neonatorum is a benign, self-limited rash in full-term neonates characterized by erythematous macules with central pustules that spare the palms and soles; it requires only reassurance and routine care.

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