Fever of Unknown Origin / Pyrexia of unknown origin

Symptoms | Treatments

What is

Symptoms

Causes and Risk Factors

Diagnosis

Treatment

What is - Fever of Unknown Origin / Pyrexia of unknown origin

Fever of unknown origin (FUO), also known as pyreia of unknown origin (PUO), is a condition in which fever in excess of 38.3C has been around for three weeks or longer, and persists despite three outpatient evaluations or 3 days in the hospital. Despite extensive investigations and initial treatment, fever persists and as the name suggests, the cause of the febrile illness is often not identified during the initial workup.

FUO / PUO can occur in otherwise healthy individuals, hospitalized patients, immunocompromised patients or patients with human immunodeficiency virus.

Symptoms of Fever of Unknown Origin / Pyrexia of unknown origin

As mentioned above, it is characterised by a prolonged febrile illness and depending on its cause, the constellation of signs and symptoms may vary.

It may present as an isolated febrile illness or it could be associated with other symptoms such as headaches, joint pains, rash, lymph node enlargement, loss of weight, loss of appetite, shortness of breath, chronic cough, chronic diarrhoea. This list of common clinical signs and symptoms is not exhaustive.

Fever of Unknown Origin / Pyrexia of unknown origin - Causes and Risk Factors

There are many causes of FUO / PUO, ranging from infections to autoimmune diseases to malignancies. Some common causes of FUO / PUO include the following:

Infections such as tuberculosis, human immunodeficiency virus infection, infective endocarditis, undrained abscesses and viral infections.
Autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, temporal arteritis, polymyalgia rheumatica, mixed connective tissue disorders, adult onset Still’s disease, etc.
Hematological malignancies such as lymphoma and leukemia.
Solid organ malignancies such as hepatocellular carcinoma and renal cell carcinoma.
Miscellaneous conditions including drug fever, hypersensitivity syndrome and Kikuchi’s disease

Unfortunately, in 10-20% of cases, the cause of the FUO / PUO remain undiagnosed.

Diagnosis of Fever of Unknown Origin / Pyrexia of unknown origin

The diagnosis of FUO / PUO is based on comprehensive history and physical examination. Repeated consults to retake the history and repeat physical examination is often necessary to help the physicians make the diagnosis and find out the exact cause of the prolonged fever.

The wide range of tests performed thereafter are often adjuncts to help the physician make the diagnosis. The tests include blood tests, key imaging studies and may include invasive diagnostic procedure. The selection of tests is guided by the presenting clinical complaint.

More than the technology involved, getting to the root cause of FUO / PUO requires experienced clinicians, as well as patience on the part of patient and his/her family. Often, a multi-disciplinary team of doctors is involved. This is usually led by the infectious diseases team to pinpoint the exact cause of the FUO / PUO.