An 18-day-old male infant is brought to the pediatric emergency department due to a 24-hou… — USMLE Step 2 CK

An $18$ -day-old male infant is brought to the pediatric emergency department due to a $24$ -hour history of fever, irritability, and poor feeding. The infant was born full-term at $39$ weeks gestation via an uncomplicated spontaneous vaginal delivery and was discharged home on the second day of life.

Vital signs show a temperature of $38.8^\circ\text{C}$ ( $101.8^\circ\text{F}$ ), a heart rate of $185/\text{min}$ , and a respiratory rate of $58/\text{min}$ . Physical examination reveals a lethargic infant who cries inconsolably when handled. The anterior fontanelle is full and tense. The infant's skin exhibits numerous $1$ - to $2$ - $\text{mm}$ pearly white papules across the nasal bridge and cheeks without surrounding erythema. Auscultation of the lungs is clear, and capillary refill is $3$ seconds.

Which of the following is the most appropriate next step in management?

Perform a lumbar puncture, obtain a blood culture, and initiate ampicillin and cefotaximeAnswer
B
Obtain a swab of the facial lesions for viral polymerase chain reaction and initiate intravenous acyclovir
C
Administer intravenous vancomycin and meropenem prior to obtaining cerebrospinal fluid studies
D
Administer nebulized albuterol and arrange for admission for supportive respiratory care
E
Administer intravenous furosemide and obtain an urgent transthoracic echocardiogram

Answer

The most appropriate next step is to perform a lumbar puncture, obtain a blood culture, and initiate ampicillin and cefotaxime.

This infant presents with fever, irritability, lethargy, and a full anterior fontanelle, which are hallmark signs of late-onset neonatal meningitis. In neonates (age <28 days), community-acquired meningitis is most commonly caused by Group B Streptococcus, E. coli, and Listeria monocytogenes. The most appropriate next step is to obtain appropriate cultures (blood and cerebrospinal fluid via lumbar puncture) followed immediately by empiric antibiotics. The regimen of choice is ampicillin (to cover Listeria and susceptible Gram-positive organisms) and a third-generation cephalosporin such as cefotaxime (which has excellent blood-brain barrier penetration and covers Gram-negative organisms). The facial lesions described are milia, which are benign retention cysts of pilosebaceous units requiring no intervention.

Step-by-Step Solution

Analyze the clinical presentation and vital signs.

The 18-day-old infant presents with fever, irritability, lethargy, and a full, tense anterior fontanelle.

These findings are classic signs of central nervous system infection, specifically late-onset neonatal meningitis.

Evaluate the cutaneous findings described in the physical exam.

The presence of 1- to 2-mm pearly white papules on the nose and cheeks without erythema is identified as milia.

Milia are benign keratin-filled cysts common in newborns. Recognizing this prevents misdiagnosis of an infectious rash like herpes simplex virus (HSV), which typically presents with clustered vesicles on an erythematous base.

Determine the appropriate diagnostic and therapeutic intervention for suspected neonatal meningitis.

The infant requires immediate diagnostic fluid sampling (blood and cerebrospinal fluid cultures) followed by empiric intravenous antibiotics.

To accurately diagnose the pathogen without delaying potentially life-saving treatment.

Select the correct empiric antibiotic regimen for a neonate < 28 days old.

Ampicillin and a third-generation cephalosporin (cefotaxime) are selected.

This combination provides excellent central nervous system penetration and covers the most common community-acquired pathogens: Group B Streptococcus, E. coli, and Listeria monocytogenes.

Key Concept

Late-Onset Neonatal Meningitis and Benign Skin Findings

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