Explanation:
With this presentation, one must think about the causes of stridor in children. Of the above options, only anaphylaxis, bacterial tracheitis, croup and epiglottitis produce stridor. Acute bronchiolitis would present with a viral prodrome that progresses into a productive cough and possibly wheezing, but would not produce stridor or a bark-like cough. Acute bronchiolitis occurs due to a viral infection, which is usually caused by the Respiratory Syncytial Virus (RSV). Pertussis would have a weeklong prodrome resembling that of an upper respiratory tract infection, however it would then progress into a persistent dry cough, often with coughing fits, after roughly the second week of symptoms. Allison doesn’t fit this description, as her presentation is too acute for the cough to be caused by pertussis. In addition, the cough is said to be bark-like, not persistent and with coughing fits, as is seen in pertussis. Postnasal drip would not present in this fashion, but would instead present as a chronic cough and persistent throat clearing. Pneumonia can look like the initial phase of this presentation with non-specific symptoms. As pneumonia progresses, it is common to see accessory muscles being used to breathe, along with suprasternal and intercostal indrawing, as well as nasal flaring. On physical exam you may also hear crepitations, however, you would not hear stridor or a bark like cough.

Bacterial tracheitis, croup, and epiglottitis can all produce stridor, and as such would be important to keep on a differential diagnosis. Anaphylaxis also produces stridor, however it would be very unlikely for an anaphylactic reaction to progress over 2 days to cause stridor, and would be more likely if it occurred within minutes. Although epiglottitis does not typically produce a bark like cough, the high fever and generally unwell appearance of Allison, along with the stridor warrant it remaining on the differential diagnosis.