Fever of unknown origin

Fever of unknown origin (FUO), refers to a condition in which the patient has an elevated temperature (fever) but despite investigations by a physician no explanation has been found. Fever of unknown origin (FUO), refers to a condition in which the patient has an elevated temperature (fever) but despite investigations by a physician no explanation has been found. If the cause is found it is usually a diagnosis of exclusion, that is, by eliminating all possibilities until only one explanation remains, and taking this as the correct one. Extrapulmonary tuberculosis is the most frequent cause of FUO.Drug-induced hyperthermia, as the sole symptom of an adverse drug reaction, should always be considered. Disseminated granulomatoses such as tuberculosis, histoplasmosis, coccidioidomycosis, blastomycosis and sarcoidosis are associated with FUO. Lymphomas are the most common cause of FUO in adults. Thromboembolic disease (i.e. pulmonary embolism, deep venous thrombosis) occasionally shows fever. Although infrequent, its potentially lethal consequences warrant evaluation of this cause. Endocarditis, although uncommon, is another important etiology to consider. An underestimated reason is factitious fever. Patients frequently are women that work, or have worked, in the medical field and have complex medical histories. Bartonella infections are also known to cause fever of unknown origin. Here are the known causes of FUO. Although most neoplasms can present with fever, malignant lymphoma is by far the most common diagnosis of FUO among the neoplasms. In some cases the fever even precedes lymphadenopathy detectable by physical examination. A comprehensive and meticulous history (i.e. illness of family members, recent visit to the tropics, medication), repeated physical examination (i.e. skin rash, eschar, lymphadenopathy, heart murmur) and myriad laboratory tests (serological, blood culture, immunological) are the cornerstone of finding the cause. Other investigations may be needed. Ultrasound may show cholelithiasis, echocardiography may be needed in suspected endocarditis and a CT-scan may show infection or malignancy of internal organs. Another technique is Gallium-67 scanning which seems to visualize chronic infections more effectively. Invasive techniques (biopsy and laparotomy for pathological and bacteriological examination) may be required before a definite diagnosis is possible. Positron emission tomography using radioactively labelled fluorodeoxyglucose (FDG) has been reported to have a sensitivity of 84% and a specificity of 86% for localizing the source of fever of unknown origin. Despite all this, diagnosis may only be suggested by the therapy chosen. When a patient recovers after discontinuing medication it likely was drug fever, when antibiotics or antimycotics work it probably was infection. Empirical therapeutic trials should be used in those patients in which other techniques have failed.