Fever of unknown origin

Fever of unknown origin is diagnosed when it is above 38.3 degrees on several occasions for more than 3 weeks. It poses a challenge for the internist and requires a thorough clinical examination preceded by a complete interrogation. In these cases, no diagnosis has been made after the patient is studied for a week in the hospital or goes to 3 outpatient clinics. A fever of unknown origin, therefore, means a real challenge for the internist, where the most frequent causes are infections, neoplasms (tumors) or collagen diseases such as lupus, polymyositis or vasculitis.

There is, on the other hand, that fever of unknown origin that lasts more than 6 months. Fever of this type is not usually due to an infection , and is due to unusual diseases or unknown causes , some causes that if not found, the prognosis is usually favorable. In which, on the contrary, we do not find the diagnosis, we could describe them as true fevers of unknown origin.

It consists of informing the patient well and avoiding empirical treatment, that is, supplying antibiotics to the patient despite not having a definitive diagnosis.

Once the diagnosis is known, the treatment is that of the disease responsible for the fever.

In addition to fever of classical unknown origin, there are other types of fever, such as:

In patients without infection at the time of admission, if the fever lasts 3 days including 2 more of the investigation, the diagnosis is usually septic thrombophlebitis, sinusitis, clostridium difficile colitis or drug fever .

Patients with neutropenia with neutrophils less than 500, the diagnosis points more to a perianal infection, aspergillosis or candidemia.

Finally, another group of patients, those who have HIV and suffer a fever that lasts 3 days in a hospitalized patient or 3 weeks in an outpatient, the diagnosis is usually tuberculosis, non-hodgkin's lymphoma or drug fever.