Uncommon Presentations of a Common Problem: Fever of Unknown Origin– Among the most challenging medical dilemmas encountered by the practicing physician is that of appropriately assessing and correctly diagnosing a child presenting with a fever of unknown origin (FUO). To the ancient physician, prolonged fevers of infectious etiology were of particular concern. Keefer and Leard, in their 1955 text, noted that FUO represents a classic internal medicine problem, considered by many to be the ultimate diagnostic challenge for an astute clinician. This remains just as true today for pediatricians and other physicians providing medical care for children.
In 1961, the term “FUO” was first defined as well documented fever lasting more than three weeks, with a temperature of 101ºF (38.3ºC) or higher, and remaining undiagnosed for a week after extensive hospital testing. With regard to children, the definition was refined further in 1992 by Lorin and Feigin as the presence of a fever for eight or more days in a child in whom a careful and thorough history and physical examination and preliminary laboratory data fail to reveal a probable cause of fever. It is generally accepted that since viral infections, which often can be the cause for fever in childhood, generally resolve within a week, any unexplained fever persisting longer than 1 week warrants diagnostic investigation.
Most pediatricians confronted with a patient having a FUO will experience considerable difficulty addressing the numerous diagnostic possibilities and an appropriate, well thought out, pathway for assessment. In general, the initial workup will consist of a battery of standard laboratory tests and/or diagnostic imaging procedures. When the results of these studies are determined to be inconclusive, the attending physician often turns to a consultant for an opinion as to next steps. In most cases, that consultant is an infectious disease specialist.
Approach and perform the diagnostic evaluation workup for pediatric and adolescent patients presenting with a fever of unknown origin. List and differentiate the possible diagnoses consistent with the history and physical examination findings discussed in each of the two cases presented.
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