Summary
Fever of unknown origin (FUO) is defined as a temperature >38.3°C (100.9°F) lasting for more than 3 weeks, with no obvious source despite appropriate investigation. [1] Fluctuations in body temperature of up to 1.1°C (2°F) are normal. Elevated body temperature can be physiological, or caused by pathological processes such as infection, inflammatory processes, or malignancy. The diagnosis occurs across all age groups and affects both sexes equally. However, age is an important factor in forming a differential diagnosis. Epidemiological trends in the aetiology of FUO vary throughout the world. A careful history includes recent travel. TB and malaria remain common causes throughout the world, although are less commonly encountered in non-endemic countries. [2] However, endemic infectious diseases are still the most likely aetiologies. Local epidemiological data must be taken into account.
Of the broad most common subgroups of differential diagnosis (i.e., infections, malignancies, or autoimmune diseases), infectious diseases remain the most common aetiological category for FUO.
Differential diagnosis
- Common
- Uncommon
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- Dental abscesses
- Osteomyelitis
- Prostatitis, acute or chronic
- Cytomegalovirus infection
- Epstein-Barr virus infection
- Rheumatic fever
- Lyme disease
- Chronic myeloid leukaemia
- Lymphoma
- Metastatic carcinoma, primary unknown
- Renal cancer
- Colorectal cancer
- Pancreatic cancer
- Hepatocellular carcinoma
- Myelodysplastic syndrome
- Adult-onset Still's disease
- Polymyalgia rheumatica
- Giant cell arteritis
- Systemic lupus erythematosus
- Inflammatory bowel disease
- Rheumatoid arthritis
- Reiter's syndrome
- Drug-induced fever
- Cirrhosis, complicated
- Hepatitis
- Deep vein thrombosis
- Sarcoidosis
- Familial Mediterranean fever
- Malaria
- Typhoid fever
- Rocky Mountain spotted fever
- Ascariasis
- Tularaemia
- Brucellosis
- Psittacosis
- Q fever
- Phaeochromocytoma
- Hyperthyroidism
- Munchausen syndrome
