[Fever without focus and fever of unknown origin in childhood].
Fever is one of the most common presenting symptoms in children. In the majority of cases the underlying cause is easily diagnosed and if necessary a treatment initiated. In case of absent localising symptoms and signs (fever without a focus) investigations rapidly need to be undertaken in particular in newborns and infants. Persisting daily fever for more than two weeks are called fever of unknown origin. Diagnosis of etiology of fever of unknown origin is challenging. In approximately half of the cases an infectious cause is found; inflammatory and mailgnant diseases account for 5 to 10% of the cases. Despite a systematic and interdisciplinary approach the etiology remains unknown in up to a quarter of cases. This review discusses differential diagnoses, suggested investigations and treatment for fever without a focus and fever of unknown origin.