Fever in Childhood: Part 2: fever of unknown origin.

The most common cause of fever of unknown origin (FUO) is infectious disease, followed less frequently by collagen vascular disease, and malignancy. Most children with FUO have a common disorder that is atypical in presentation. A history and physical examination are vital and should be repeated until a diagnosis is established. Specific laboratory tests and diagnostic imaging studies should be ordered based on the clinical evaluation. Children with FUO have a better prognosis than adults; most can expect full recovery.