About the disease

A diagnosis of fever of unknown origin is diagnosed if this is the primary condition, without any underlying causes or secondary symptoms. It is usually diagnosed if it lasts for longer than 3 weeks and it does not subside even after the usual antipyretic treatment. In some people, the fever tends to be recurrent and develops suddenly without any other symptoms. A person is considered feverish if their temperature is higher than 38.3°C for a sustained period of time.   

Generally, there are four major types of fever of unknown origin. The first type is called classic. This fever develops in healthy people who have no other apparent health conditions. However, this type of fever of unknown origin can sometimes be caused by a hidden infection, which manifests itself only as a fever. Sometimes, leukemia manifests itself in this way in the beginning stages. Neoplasms can also be the cause of fever.

The second type of fever of unknown origin is called nonsomical. It tends to develop in people who have been hospitalized with another condition. It can be caused by deep inflammation of tissue or by some other conditions, which can be discovered only during additional examination.

People who have any type of immune deficiency are likely to develop a fever of unknown origin at some point of their life. This is the third type of this condition. It can develop in people with autoimmune diseases or in people with a compromised immune system. Improving the general state of the immune system is usually the key to treating the fever of in this case.

The fourth and last type of fever of unknown origin is ascribed to HIV patients, who may develop a fever due to the infection and damage to the immune system.  Sometimes, a fever can also indicate malignancy or problems with inner organs, which is why patients are advised to have all of their bodily systems checked.

In most cases, the cause of such a fever is an infection. According to Healthline, up to 40% of all cases of fever of unknown origin can be ascribed to an infection.

Symptoms

• Temperature higher than 38.3°C
• General weakness
• Fatigue
• Perspiration
• Night sweats, which can suddenly turn into chills
• Headache
• Muscle and joint pain in some cases
• Confusion, in rare cases
• Hallucinations, in rare cases

Diagnosis

• During a general examination, the doctor will ask if the patient has had any colds or infections lately.
• The doctor will listen to the patient’s heart and will check their skin for signs of a rash or swelling, which often accompanies long-term fevers.
• The doctor will ask if the patient has any autoimmune conditions that could be affecting the immune system.
• A blood test can determine whether or not the patient has an infection. It can also check the white blood cell count, to see if the immune system is functioning normally. If there is a suspicion of HIV infection, the patient is advised to undergo a test for HIV.
• A urinalysis can indicate an inflammation or infection in the body.
• Imaging tests help doctors to check the organs for any possible malformations or damage.

Treatment

• The most important thing in treatment of such a fever is to eliminate its cause.
• Doctors prescribe antibiotics and anti-inflammatory drugs if the cause of fever was an infection. Antiviral therapy can be prescribed as well, if the cause of the fever was a virus.
• If a patient is diagnosed with HIV, they will be prescribed antiretroviral therapy.

Authors: Dr. Nadezhda Ivanisova, Dr. Sergey Pashchenko