A 4-week-old male infant is brought to the emergency department in January due to a 2-day … — USMLE Step 2 CK

A 4-week-old male infant is brought to the emergency department in January due to a 2-day history of nasal congestion, cough, and fast breathing. His 3-year-old sister recently recovered from a mild upper respiratory tract infection. The infant was born at term via an uncomplicated vaginal delivery. Vital signs show a temperature of $37.4^\circ\text{C}$ ( $99.3^\circ\text{F}$ ), heart rate of $165/\text{min}$ , respiratory rate of $68/\text{min}$ , and oxygen saturation of $89\%$ on room air. He appears moderately distressed but is consolable. Physical examination reveals prominent subcostal retractions, nasal flaring, and diffuse bilateral expiratory wheezes. Skin examination shows multiple small, erythematous papules and pustules confined strictly to the cheeks and forehead, with no grouped vesicles. The remainder of the examination is unremarkable. Which of the following is the most appropriate next step in management?

Admission for supportive care including supplemental oxygen and intravenous fluidsAnswer
B
Administration of nebulized albuterol and oral dexamethasone
C
Lumbar puncture and initiation of intravenous acyclovir
D
Blood and urine cultures followed by intravenous ampicillin and gentamicin
E
Intramuscular administration of palivizumab and intranasal live-attenuated influenza vaccine

Answer

Admission for supportive care including supplemental oxygen and intravenous fluids

The correct answer emphasizes supportive management. This 4-week-old infant presents with classic acute viral bronchiolitis, characterized by URI symptoms progressing to lower respiratory tract signs (wheezing, tachypnea, retractions) in the winter months. Because he has oxygen saturation below

90\%

and significant respiratory distress, inpatient admission for supplemental oxygen and intravenous fluids is required. The facial rash described is neonatal cephalic pustulosis, a benign condition mediated by Malassezia species that peaks at 3-4 weeks of age and requires no systemic intervention. Furthermore, because the infant is afebrile and has a distinct viral syndrome, invasive bacterial and viral testing is not routinely indicated.

Step-by-Step Solution

Interpret the respiratory signs and symptoms.

The infant's age, winter presentation, URI symptoms, wheezing, and retractions strongly suggest viral bronchiolitis (most likely Respiratory Syncytial Virus).

Recognizing the classic clinical presentation of bronchiolitis is the first step in determining the appropriate management pathway.

Evaluate the patient's objective stability parameters.

The infant is hypoxic (

89\%

on room air) and highly tachypneic (

68/\text{min}

), but afebrile (

37.4^\circ\text{C}

Hypoxia and significant respiratory distress in a 4-week-old indicate a high risk for impending respiratory failure or apnea, necessitating inpatient admission rather than outpatient management.

Identify the etiology of the dermatologic findings.

The facial erythematous papules and pustules lacking grouped vesicles are diagnostic of neonatal cephalic pustulosis (neonatal acne), a benign condition.

Differentiating a benign neonatal rash from a systemic infectious exanthem (like HSV) prevents unnecessary invasive testing (LP) and antiviral administration.

Determine the indicated therapeutic intervention.

Supportive care (oxygen, hydration, nasal suctioning) is the only evidence-based treatment required.

Because the child is afebrile with a clear viral source, broad-spectrum antibiotics are not indicated. Bronchodilators and corticosteroids are ineffective for bronchiolitis.

Key Concept

Diagnosis and management of acute viral bronchiolitis and recognition of benign neonatal dermatologic conditions.

Estimated Time:1m 30s

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