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Difficulty: Very hardPediatric Infectious Diseases

A 48-hour-old term male neonate is evaluated in the newborn nursery for a newly developed skin rash. He was born via uncomplicated vaginal delivery to a 26-year-old primigravida. The mother has a history of recurrent genital herpes simplex virus (HSV) infections but had no active lesions or prodromal symptoms at the time of delivery. She took suppressive oral acyclovir from 36 weeks of gestation. The infant's temperature is 37.1°C (98.8°F), heart rate is 145/min, and respiratory rate is 40/min. He is feeding well and has normal tone. Physical examination reveals widespread 2- to 3-mm firm, pale yellow pustules surrounded by a prominent erythematous macular base (a "flea-bitten" appearance), distributed over his trunk, face, and proximal extremities. The palms and soles are spared. The remainder of the examination is unremarkable. Which of the following is the most appropriate next step in the management of this patient?

  1. Reassurance and continued routine newborn careAnswer
  2. B
    Microscopic examination of a Wright-stained smear of a pustule
  3. C
    Swab the pustules for herpes simplex virus polymerase chain reaction and initiate intravenous acyclovir
  4. D
    Obtain blood, urine, and cerebrospinal fluid cultures and start intravenous ampicillin and gentamicin
  5. E
    Isolate the infant and initiate topical mupirocin therapy

Answer

Reassurance and continued routine newborn care is the most appropriate next step.
The correct answer is reassurance and continued routine newborn care. The infant has a classic presentation of erythema toxicum neonatorum (ETN), a benign, self-limited rash characterized by 2- to 3-mm firm, pale yellow papules or pustules surrounded by a prominent erythematous flare (a "flea-bitten" appearance). It typically appears on the second or third day of life, involves the trunk and proximal extremities, and characteristically spares the palms and soles. In a well-appearing infant, ETN is diagnosed clinically and resolves without intervention in 5 to 14 days. The maternal history of HSV serves as a distractor in this scenario. Because the mother has a history of recurrent (not primary) genital HSV, had no active lesions or prodromal symptoms at the time of delivery, and was on appropriate suppressive therapy, the infant's risk of HSV acquisition is extremely low (<1%). Furthermore, neonatal HSV cutaneous disease typically presents with clustered vesicles on an erythematous base (often at sites of presenting parts or trauma) rather than scattered pustules with a macular flare, and usually appears slightly later (days 5-14 of life). Therefore, aggressive empiric antiviral therapy and infectious workups are not indicated.

Step-by-Step Solution

1
Analyze the infant's clinical status and rash morphology.
The patient is a well-appearing, normothermic neonate with scattered pale pustules on a prominent erythematous base ('flea-bitten' appearance) that spares the palms and soles.
Accurate morphologic description is required to differentiate benign neonatal rashes (like Erythema Toxicum Neonatorum) from serious infectious etiologies.
2
Evaluate the risk of neonatal herpes simplex virus (HSV) transmission.
The mother has a history of recurrent genital HSV, but had no active lesions at delivery and was adherent to suppressive acyclovir. The infant's rash consists of scattered pustules with macular flares, not the clustered vesicles on an erythematous base typical of HSV.
Maternal recurrent HSV without active lesions at delivery carries an exceptionally low risk (<1%) of neonatal transmission, allowing the clinician to prioritize alternative, more likely diagnoses for the rash.
3
Determine the most appropriate management plan based on the synthesized clinical picture.
The diagnosis is clinically confirmed as Erythema Toxicum Neonatorum, a benign and self-limited condition. No laboratory testing or empiric pharmacotherapy is indicated.
Avoiding unnecessary invasive testing and empiric treatments (such as acyclovir or broad-spectrum antibiotics) is the standard of care for well infants with classic benign presentations.

Key Concept

Erythema toxicum neonatorum is a benign, self-limited rash characterized by scattered pustules on an erythematous base sparing the palms and soles; it is diagnosed clinically and managed with reassurance, even in the presence of low-risk maternal infectious histories such as recurrent HSV without active lesions at delivery.
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Topics

Pediatric Infectious Diseases

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