Fever of Unknown Origin: A Clinical Approach

Abstract

Fevers of unknown origin remain one of the most difficult diagnostic challenges in medicine. Because fever of unknown origin may be caused by over 200 malignant/neoplastic, infectious, rheumatic/inflammatory, and miscellaneous disorders, clinicians often order non-clue-based imaging and specific testing early in the fever of unknown origin work-up, which may be inefficient/misleading. Unlike most other fever-of-unknown-origin reviews, this article presents a clinical approach. Characteristic history and physical examination findings together with key nonspecific test abnormalities are the basis for a focused clue-directed fever of unknown origin work-up.

Pyrexia of unknown origin: causes, investigation and management

“…In the Australian context, rebate of cost is only provided for use of whole body FDG‐PET CT for work‐up, staging and follow‐up of certain malignancies. In case the cost is prohibitive, a CT scan with intravenous contrast would be appropriate, and many physicians have found gallium scans to be a useful diagnostic tool . More invasive diagnostics, such as bone marrow biopsy, temporal artery biopsy and transoesophageal biopsy (TOE), should not be performed routinely and only be performed if indicated by previous history, examination or investigations.…”

“…There are, however, several diagnoses, which, if suspected, should be treated empirically until they can be confirmed or excluded. These include infective endocarditis, giant cell arteritis and miliary or central nervous system tuberculosis …”

Evaluation of Spleen Glucose Metabolism Using 18F-FDG PET/CT in Patients with Febrile Autoimmune Disease

“…The general principles of treatment can be very different depending on the underlying condition; immune suppression can be therapeutic in autoimmune diseases, though potentially deleterious in infection. Despite the distinct pathogeneses and treatments, both diseases share common clinical features, including leukocytosis and elevated acute-phase reactants, such as erythrocyte sedimentation rate and C-reactive protein (5). Fever can be the main clinical feature of both autoimmune and infectious diseases, posing diagnostic challenge for distinguishing autoimmune diseases from infection.…”

Rol del PET/CT con 18FDG en patología no neoplásica

“…Considerando lo anterior, las indicaciones de PET/ CT utilizando FDG han aumentado en los últimos años, siendo una de las más frecuentes el estudio de fiebre de origen desconocido (FOD) 8 . El FOD se define clásicamente como fiebre de 3 semanas con episodios de temperatura corporal mayor a 38.3 °C sin signos localizadores o una causa evidente, en la que no se logra un diagnóstico pese al estudio clínico, de laboratorio e imagenológico básico 9 . De acuerdo a la literatura estos casos corresponden en un 20 a 30% a infecciones, en un 15 a 25% a neoplasias y en otro 25% a causas inflamatorias.…”

“…De acuerdo a la literatura estos casos corresponden en un 20 a 30% a infecciones, en un 15 a 25% a neoplasias y en otro 25% a causas inflamatorias. Hasta en un 25% de los casos no se encuentra una causa específica 9 . Otras indicaciones para el uso de PET/CT son la confirmación diagnóstica de infecciones óseas (especialmente en el contexto de espondilodiscitis y pie diabético), y el control de extensión de algunas enfermedades inflamatorias como sarcoidosis, enfermedad inflamatoria intestinal, vasculitis, artritis reumatoidea y pericarditis, así como también la evaluación de respuesta al tratamiento de éstas 10,11 .…”