Fever of unknown origin causes

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Naresh Mullaguri, M.B.B.S. [2]

Synonyms and Keywords: febris continua e causa ignota; febris e causa ignota; febris E.C.I.; FUO; PUO; pyrexia of unknown origin


Common Causes

  • Extrapulmonary tuberculosis[1] - most frequent cause of fever of unknown origin.
  • Drug fever - adverse reactions of medications should always be considered as an important cause before starting actual evaluation for FUO.
  • Histoplasmosis
  • Coccidioidomycosis
  • Blastomycosis - any systemic granulomatous disease can be a cause of FUO.
  • Sarcoidosis - one of the important differential diagnosis for FUO in African-american population.
  • Lymphoma - most common cause of FUO in adults.
  • Pulmonary embolism
  • Deep venous thrombosis
  • Endocarditis - although it is a rare cause, it is always important to think over it as one of the differential diagnosis.
  • Factitious fever[2]- most of the times it is an underestimated cause of FUO but it is often important to consider it in people who worked in the medical field and majority of them are females.

Causes by Organ System

Cardiovascular Endocarditis, Deep vein thrombosis, Thrombophlebitis
Chemical / poisoning Bismuth
Dermatologic No underlying causes
Drug Side Effect Allopurinol, Amphotericin B, Aminoglutethimide, Barbiturates, Bismuth, Chlorpromazine, Docetaxel, Ethotoin, GMCSF, Levomepromazine, Methyldopa, Perazine, Phenophthalein, Pipothiazine, Promazine, Penicillin, Phenytoin, Quinidine, Rifampicin
Ear Nose Throat Periodic fever aphthous pharyngitis and cervical adenopathy, Sinusitis
Endocrine No underlying causes
Environmental No underlying causes
Gastroenterologic Cirrhosis of liver, Crohn's disease, Ulcerative Colitis, Whipple's disease, Choledochal cyst, Cholangitis
Genetic No underlying causes
Hematologic Angioimmunoblastic lymphadenopathy with dysproteinaemia, Hyperimmunoglobulinemia D and periodic fever syndrome
Iatrogenic No underlying causes
Infectious Disease Lung abscess, Subdiaphragmatic abscess, Liver abscess, Pyelonephritis, Salmonella typhi, Osteomyelitis, Gonorrhoea, Leptospirosis, Q fever, Endocarditis, Tularaemia, Scrub typhus, Relapsing fever, Rickettsia akari, Boutonneuse fever, Mycobacterium tuberculosis, Yersinia enterocolitica, Periodic fever aphthous pharyngitis and cervical adenopathy, Ehrlichiosis, Atypical pneumonia, Cyclical neutropenia, Xanthogranulomatous pyelonephritis, Streptococcus suis, Catheter infections, Lepromatous leprosy, Treponema pallidum, Neisseria meningiditis, UTI, Borrelia burgdorferi, Mycobacterium kansasii, Mycobacterium avium-intracellulare, Sinusitis, Actinomycosis, Yersinia pseudotuberculosis, Leptospira hebdomadis, Listeria monocytogenes, Brucellosis, Blastomycosis, Candida albicans, Allergic bronchopulmonary aspergillosis, Invasive aspergillosis, Cryptococcus neoformans, Psittacosis, Coccidioidomycosis, Histoplasmosis, Malaria, Toxoplasma, Sleeping sickness, Entamoeba histolytica, Visceral leishmaniasis, Fasciola hepatica, Epstein-Barr virus, Hepatitis B, HIV-1 disease, Newcastle disease
Musculoskeletal / Ortho Osteomyelitis, Discitis, Polymyalgia rheumatica
Neurologic Hereditary sensory and autonomic neuropathy type 3, Vitamin B12 deficiency
Nutritional / Metabolic Vitamin B12 deficiency
Obstetric/Gynecologic No underlying causes
Oncologic Renal adenocarcinoma, Hodgkin's lymphoma, Pancreatic cancer, Angioimmunoblastic lymphadenopathy with dysproteinaemia, Paraneoplastic syndrome, Atrial myxoma
Opthalmologic No underlying causes
Overdose / Toxicity No underlying causes
Psychiatric Factitious fever
Pulmonary Lung abscess, Allergic bronchopulmonary aspergillosis, Invasive aspergillosis
Renal / Electrolyte Acute pyelonephritis, Xanthogranulomatous pyelonephritis
Rheum / Immune / Allergy Polyarteritis nodosa, Systemic lupus erythematosus, Polymyalgia rheumatica, Sarcoidosis, Polymyositis, Temporal arteritis, Juvenile chronic arthritis, Hyperimmunoglobulinemia D and periodic fever syndrome, Wegener's granulomatosis, Recurrent hereditary polyserositis, Disseminated Intravascular Coagulation, Still's Disease, Rheumatoid disease, Whipple's disease, Retroperitoneal fibrosis, Crohn's disease, Ulcerative colitis, Schnitzler syndrome
Sexual No underlying causes
Trauma No underlying causes
Urologic No underlying causes
Dental No underlying causes
Miscellaneous Surgery complication, Fabry's disease

Causes by Alphabetical Order

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  1. Harrison's Principles of Internal Medicine 16th Edition, The McGraw-Hill Companies, ISBN 0-07-140235-7
  2. Mandell's Principles and Practices of Infection Diseases 6th Edition (2004) by Gerald L. Mandell MD, MACP, John E. Bennett MD, Raphael Dolin MD, ISBN 0-443-06643-4 · Hardback · 4016 Pages Churchill Livingstone
  3. Méndez-Tovar LJ, Manzano-Gayosso P, Cumplido-Uribe C, Hernández-Hernández F, Ramos-Hernández J, López-Martínez R (2012). "[Invasive mycosis, immunocompromise and fever of unknown origin]". Rev Med Inst Mex Seguro Soc (in Spanish; Castilian). 50 (6): 609–14. PMID 23331746.
  4. Zhang J, Chen B, Xu X; et al. (2012). "Clinical features of 66 lymphoma patients presenting with a fever of unknown origin". Intern. Med. 51 (18): 2529–36. PMID 22989822.
  5. Aguilar-Olivos N, Del Carmen Manzano-Robleda M, Gutiérrez-Grobe Y, Chablé-Montero F, Albores-Saavedra J, López-Méndez E (2013). "Granulomatous hepatitis caused by Q fever: a differential diagnosis of fever of unknown origin". Ann Hepatol. 12 (1): 138–41. PMID 23293205. Unknown parameter |month= ignored (help)
  6. Chandrankunnel J, Cunha BA, Petelin A, Katz D (2012). "Fever of unknown origin (FUO) and a renal mass: renal cell carcinoma, renal tuberculosis, renal malakoplakia, or xanthogranulomatous pyelonephritis?". Heart Lung. 41 (6): 606–9. doi:10.1016/j.hrtlng.2012.03.008. PMID 22658892.
  7. Petelin A, Johnson DH, Cunha BA (2012). "Fever of unknown origin (FUO) due to systemic lupus erythematosus (SLE) presenting as pericarditis". Heart Lung. doi:10.1016/j.hrtlng.2012.07.002. PMID 22980227. Unknown parameter |month= ignored (help)