Fever of unknown origin: a follow-up investigation of 34 patients.

34 patients hospitalized for fever of unknown origin (FUO) were subjected to a follow-up investigation on the average 5 yr after the hospital stay. Two patients had died of a disease related to FUO: one had adenocarcinoma with an unknown primary site and the other a supposed autoimmune disease. In one case the cause of FUO was a periappendicular abscess. A woman continued to have periods of fever with high ESR. In the remaining 30 cases the cause of FUO had apparently been a self-limited, benign disease. In contrast to an earlier series from our clinic, no cases of tuberculosis were revealed.