Fever of unknown origin(FUO): Causes, Work-ups & Managements
The febrile illness, for which clinically clear etiology is not known, is often referred to as the Fever of unknown origin (FUO), but the use of the term is not clearly defined. Most febrile illness comes about before diagnosis, or before showing any characteristic findings that may lead to diagnosis. In the end, FUO is a persistent febrile illness that does not establish etiology even though it uses intensive evaluation and diagnostic tools.
Causes
The most common causes of FUO are infection, neoplasm, connective tissue disease, miscellaneous disease, and undiagnosed condition. First, there may be a number of infectious agents such as abscess, endocarditis, tuberculosis, and extrapulmonary tuberculosis is one of the most common causes of FUO. Malignant lymphoma is the most common cause of neoplasm, and hematologic malignancies, solid tumors, and benign tumors may be the cause of FUO. Noninfectious inflammatory disease is also a common cause of FUO, other than miscellaneous conditions, inherited and metabolic disease, and thermoregulatory disorders.
Work-ups
The diagnosis of FUO should be based on a broad and thorough family history and recent history of visits to overseas travel and drug use. Repeated physical examinations of items such as skin rash, eschar, lymphadenopathy, and heart murmur are required, and numerous laboratory tests are required, including serological, blood culture, and immunological laboratory tests. USG, CT, and PET-CT may be required to remove malignancy.
Managements
Despite numerous tests, this diagnosis is often made only by selected treatments. That is, the diagnosis is made by seeing the treatment effect. For example, in the case of a drug fever, the fever will go down after the drug is broken, and if it is an infection, fever will be caused by antibiotics.
In the case of FUO, treatment is avoided as much as possible before diagnosis to avoid the possibility of masking the cause. Non-specific therapies are rarely effective and most of them delay the diagnosis. However, when the patient is acutely ill or eventually unable to make a conclusion, the patient is empirically treated with antibiotics or steroids.
Causes
The most common causes of FUO are infection, neoplasm, connective tissue disease, miscellaneous disease, and undiagnosed condition. First, there may be a number of infectious agents such as abscess, endocarditis, tuberculosis, and extrapulmonary tuberculosis is one of the most common causes of FUO. Malignant lymphoma is the most common cause of neoplasm, and hematologic malignancies, solid tumors, and benign tumors may be the cause of FUO. Noninfectious inflammatory disease is also a common cause of FUO, other than miscellaneous conditions, inherited and metabolic disease, and thermoregulatory disorders.
Work-ups
The diagnosis of FUO should be based on a broad and thorough family history and recent history of visits to overseas travel and drug use. Repeated physical examinations of items such as skin rash, eschar, lymphadenopathy, and heart murmur are required, and numerous laboratory tests are required, including serological, blood culture, and immunological laboratory tests. USG, CT, and PET-CT may be required to remove malignancy.
Managements
Despite numerous tests, this diagnosis is often made only by selected treatments. That is, the diagnosis is made by seeing the treatment effect. For example, in the case of a drug fever, the fever will go down after the drug is broken, and if it is an infection, fever will be caused by antibiotics.
In the case of FUO, treatment is avoided as much as possible before diagnosis to avoid the possibility of masking the cause. Non-specific therapies are rarely effective and most of them delay the diagnosis. However, when the patient is acutely ill or eventually unable to make a conclusion, the patient is empirically treated with antibiotics or steroids.
