Introduction
Fever of unknown origin (FUO) is a challenging diagnostic dilemma.
Defined as a fever of 100.9oF
(38.3oC) or higher lasting at least three weeks with
an unrevealing diagnostic work up1, FUO’s in adults
typically represent unusual presentations of common illnesses. Most
often, the condition resolves without a specific diagnosis being
made2.
The differential diagnosis for FUO is extensive. A helpful approach is
to consider infectious, inflammatory, and malignant diseases, as well as
miscellaneous conditions such as thyroiditis, thromboembolic disease,
and factitious fever. A comprehensive history emphasizing social and
travel components should precede a complete physical examination, with
laboratory tests and imaging guided by pertinent findings on history and
exam.