An 18-month-old boy is brought to the physician by his parents for fever, runny nose, and sore throat. The physician reassures the parents and recommends supportive care with plenty of fluids. He sends them home with instructions to follow up if the boy's symptoms worsen. Two days later, the infant is brought to the emergency department with persistent fever, brassy cough, and difficulty breathing. Physical examination reveals stridor. Which of the following pathogens is most likely responsible for this patient's condition?

Question

An 18-month-old boy is brought to the physician by his parents for fever, runny nose, and sore throat.  The physician reassures the parents and recommends supportive care with plenty of fluids.  He sends them home with instructions to follow up if the boy's symptoms worsen.  Two days later, the infant is brought to the emergency department with persistent fever, brassy cough, and difficulty breathing.  Physical examination reveals stridor.  Which of the following pathogens is most likely responsible for this patient's condition?

Quizplus · Accepted Answer

11ec160b_38a0_1890_9249_9d560dcffad6_MD0001_00 This child initially had fever, rhinitis, and pharyngitis, which are symptoms typical of an upper respiratory tract infection (URI). Most URIs (with or without pharyngitis) are caused by viruses, with roughly 15%-30% of childhood cases of pharyngitis and 5%-15% of adulthood cases of pharyngitis caused by bacteria. When a child with a history of recent URI develops a brassy, barking cough and breathing difficulties, it is likely that acute laryngotracheitis (croup) has developed. The dyspnea associated with croup occurs when inflamed subglottic tissue obstructs the upper airway. The characteristic stridor of croup is a sign of significant upper airway obstruction. Croup is typically caused by the standard URI viruses, with the parainfluenza viruses (members of Paramyxoviridae) most commonly responsible. (Choice A) Rhinovirus is the most common viral cause of upper respiratory infections but is an uncommon cause of viral croup. (Choice C) Togaviruses are responsible for rubella (German measles) and Eastern and Western equine encephalitis. (Choice D) Parvoviruses are responsible for aplastic crises in sickle cell anemia, erythema infectiosum (fifth disease), and hydrops fetalis. (Choice E) Caliciviruses (Norwalk virus) are responsible for viral gastroenteritis. Educational objective: Brassy, barking cough; dyspnea; and recent history of upper respiratory infection in a child are suggestive of viral laryngotracheitis (croup). The most common cause of croup is parainfluenza virus.

An 18-Month-Old Boy Is Brought to the Physician by His