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

## Overview[edit | edit source]

Classic FUO may be caused by infection, neoplasia, inflammatory , miscellaneous diseases, and undiagnosed illness.Common causes of neutropenic FUO include bacterial, fungal and viral infection.Causes of nosocomial FUO are related to hospital setting such as drugs, infections acquired during hospitalization and complications that occur during and after surgery.This may due to acute infection from HIV itself earlier or later due to opportunistic bacterial, fungal and viral infections such as mycobacteria, toxoplasma etc.

## Causes[edit | edit source]

Etiology is different for different categories of FUO:

### Classic FUO[edit | edit source]

1. Malignancies such as Hodgkin and non-Hodgkin lymphoma, myeloproliferative disorders, colorectal carcinoma and carcinoma of liver.
2. Infections such as intrabdominal and pelvic abscesses, inflammation of the endocardium, tuberculosis, cat scratch disease, CMV and EBV infections.
3. Inflammatory causes such as autoimmune diseases (systemic lupus erythematosus, Rheumatoid arthritis) and polymyalgia rheumatica.[1]
4. Miscellaneous such as Medication/drug fever,Hyperthyroidism Hematoma,Chronic pulmonary.[2]

### Neutropenic FUO[edit | edit source]

These are mostly caused by bacterial, fungal and viral infection because of the decreased neutrophil count.[3]

### HIV associated FUO[edit | edit source]

This may due to acute infection from HIV itself earlier or later due to opportunistic bacterial, fungal and viral infections such as mycobacteria, toxoplasma etc.[4]

### Nosocomial FUO[edit | edit source]

Causes of nosocomial FUO are related to hospital setting such as drugs, infections acquired during hospitalization and complications that occur during and after surgery.[2]

## References[edit | edit source]

1. ↑ Hayakawa, Kayoko; Ramasamy, Balaji; Chandrasekar, Pranatharthi H. (2012). "Fever of Unknown Origin: An Evidence-Based Review". The American Journal of the Medical Sciences. 344 (4): 307–316. doi:10.1097/MAJ.0b013e31824ae504. ISSN 0002-9629.
2. ↑ 2.0 2.1 Wright WF, Auwaerter PG (2020). "Fever and Fever of Unknown Origin: Review, Recent Advances, and Lingering Dogma". Open Forum Infect Dis. 7 (5): ofaa132. doi:10.1093/ofid/ofaa132. PMC 7237822 Check `|pmc=` value (help). PMID 32462043 Check `|pmid=` value (help).
3. ↑ Hayakawa, Kayoko; Ramasamy, Balaji; Chandrasekar, Pranatharthi H. (2012). "Fever of Unknown Origin: An Evidence-Based Review". The American Journal of the Medical Sciences. 344 (4): 307–316. doi:10.1097/MAJ.0b013e31824ae504. ISSN 0002-9629.
4. ↑ Hayakawa, Kayoko; Ramasamy, Balaji; Chandrasekar, Pranatharthi H. (2012). "Fever of Unknown Origin: An Evidence-Based Review". The American Journal of the Medical Sciences. 344 (4): 307–316. doi:10.1097/MAJ.0b013e31824ae504. ISSN 0002-9629.