fever of unknown origin in children aged three months to fifteen years

background fever of unknown origin (fuo) is defined as the presence of fever in a child for eight or more days that a careful history and physical examination and preliminary laboratory results failed to reveal the probable cause of the fever. the causes of fuo are different according to geographical regions and age. objectives the current study aimed to evaluate the common causes of childhood fuo in zahedan, iran. patients and methods a six-year retrospective study was conducted on all admitted children aged from three months to fifteen years from january 2006 to january 2012 and those with the final diagnosis of fuo were selected for the study. results finally, 1100 patients were found eligible for the study. the fuo causes were infectious diseases (55.1%), collagen vascular (4.6%), neoplasm (6.7%), miscellaneous (23.3%) and undiagnosed (10.3%). conclusions most fever of unknown origin results from atypical presentation of common diseases like tuberculosis, salmonellosis, brucellosis, and pneumonia.