A 14-day-old boy is brought to the clinic by his mother because his 4-year-old sister was … — USMLE Step 2 CK

A $14$ -day-old boy is brought to the clinic by his mother because his $4$ -year-old sister was diagnosed with chickenpox yesterday. The sister's vesicular rash first appeared $48$ hours ago, and she has been isolated in her room since. The neonate was born at $39$ weeks gestation via uncomplicated vaginal delivery. The mother's prenatal laboratory screening was unremarkable, but she notes that she grew up in an isolated rural community and has never had chickenpox. Her prenatal varicella-zoster IgG antibody titer was negative. The neonate is exclusively breastfed. The mother also reports that the infant developed mild rhinorrhea and an occasional cough this morning. His rectal temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), heart rate is $142/\text{min}$ , and respiratory rate is $42/\text{min}$ . Physical examination reveals an afebrile, alert infant in no acute distress. The lungs are clear to auscultation. Skin examination shows several scattered erythematous macules with 1- to 2-mm central yellow-white papules on the anterior chest and back. Which of the following is the most appropriate next step in management?

Administer varicella-zoster immune globulinAnswer
B
Administer intravenous acyclovir
C
Administer the live-attenuated varicella vaccine
D
Administer intravenous ampicillin and cefotaxime
E
Administer inhaled albuterol

Answer

The most appropriate next step is to administer varicella-zoster immune globulin to provide immediate passive immunity.

The correct answer is to administer varicella-zoster immune globulin. This neonate has a high-risk postnatal exposure to varicella. Protection against postnatal varicella in the neonatal period depends entirely on maternal immunity in the form of transplacental IgG. Because the mother's prenatal records confirm she is varicella IgG negative, she did not transfer protective antibodies to the infant. Therefore, this neonate is completely susceptible and is at high risk for severe, life-threatening disseminated varicella. The standard of care for a neonate whose mother lacks evidence of immunity and who has a significant postnatal exposure is the immediate administration of varicella-zoster immune globulin (VZIG) to provide passive immunity.

Step-by-Step Solution

Evaluate the patient's infectious exposure risk.

The neonate has a high-risk household exposure to a sibling with active, contagious varicella.

Postnatal varicella exposure in the neonatal period carries a high risk of severe, disseminated disease due to immature cellular immunity.

Determine the neonate's baseline immunity.

The mother is varicella-zoster IgG negative.

Neonates rely entirely on transplacental maternal IgG for protection against varicella. Since the mother is non-immune, the infant is completely susceptible.

Analyze the physical examination findings.

The physical exam reveals normal vital signs, a mild upper respiratory infection, and a rash consistent with erythema toxicum neonatorum.

Confirming the absence of systemic infection ensures the patient is still in the prophylactic window, and recognizing the rash as benign prevents unnecessary aggressive treatments.

Select the correct prophylactic intervention.

Varicella-zoster immune globulin (VZIG) is selected.

Susceptible neonates with significant postnatal exposure require VZIG for passive immunization, as the live vaccine is contraindicated in this age group.

Key Concept

Post-exposure prophylaxis for Varicella-Zoster Virus in neonates

Estimated Time:1m 30s

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