Introduction: We examined the causative diseases of patients presenting with a chief complaint of fever.Methods: The patients were new patients visiting the Department of General Medicine at the University of Tsukuba Hospital between April 2018 and March 2020. The chief complaints were obtained from the patients' medical records, categorized according to the International Classification of Primary Care Second Edition. Patients with fever (A03) as the chief complaint were enrolled and their diagnoses were investigated.Results: Of 610 eligible patients, 85 had fever as the chief complaint. Causative diseases were infectious disease in 31 patients (36%), noninfectious inflammatory diseases in nine patients (11%), malignancy in three patients (3%), others in 14 patients (16%), unknown in 19 patients (22%), and exhibiting no pathologic conditions in nine patients (11%). Specific diagnoses were viral infection for the infectious disease patients, collagen diseases for the noninfectious inflammatory disease patients, hematologic diseases for the malignancy patients, and drug-related issues for others.Conclusion: The most common cause of fever was infectious diseases. Some patients were concerned about disease even when their temperatures were in the physiologic range.

A 47-year-old man underwent a double-valve replacement involving aortic valve replacement (AVR) and mitral valve replacement (MVR) and Re-Re-DVR 6 and 8 months, respectively, after an initial DVR because of suspected prosthetic valve endocarditis. Detachment of the prosthetic mitral valve occurred during the early postoperative period, for which the patient again underwent treatment 15 and 21 months after the initial surgery. The operative findings showed that the detachment was caused by a wide cleavage of the aortic-mitral continuity. There were bacteria detected on a blood culture, and his C-reactive protein (CRP) level did not reduce at any time. On the basis of these findings, we suspected nonrheumatic inflammatory disease and started steroid therapy. His CRP level became negative, and further prosthetic mitral valve detachment did not recur.