Prolonged Fever: When to Seek Further Medical Evaluation

Fever of unknown origin (FUO)

Hello Doctor: I have been experiencing unexplained fever for two months, with temperatures ranging from around 37°C to 38°C.
I have visited an infectious disease specialist, but no cause has been identified.
My white blood cell count is approximately 4,000, and my lymphocyte percentage is 8.8.
Most of the tests have returned normal results, but the prolonged unexplained fever is concerning.
A physician has suggested hospitalization for further evaluation, but I am unsure about what to do next.
Could you please provide some advice?

danxin dao buxing, 10~19 year old female. Ask Date: 2007/03/10

Dr. Lin Mingfeng reply Internal Medicine

In clinical practice, if a patient's body temperature exceeds 38.3°C and persists for three weeks, and after one week of hospitalization with thorough examinations no cause for the fever is identified, it is termed fever of unknown origin (FUO).
There are many potential causes of FUO, exceeding one hundred, so it is essential for patients to provide a detailed medical history to their physician.
In addition to fever, other symptoms, past medical history, travel history, pet ownership, exposure history, occupational history, and sexual history are all important data for diagnosing the illness.
Based on the detailed medical history, the physician can arrange appropriate tests to more easily identify the cause of the fever.
The causes of FUO can be broadly categorized into five major groups: approximately 34% are due to infections, 20% are caused by tumors, 13% are due to connective tissue diseases, another 13% are attributed to other causes, and about one-fifth remain undiagnosed.
It is advisable to avoid a "shotgun" approach to testing and treatment for FUO, as this may not lead to an accurate diagnosis.
Furthermore, ongoing observation and follow-up examinations for FUO are quite important.
As you mentioned, you have already undergone preliminary examinations in the outpatient setting; it may be beneficial to seek a second opinion from another physician.
However, it is best to provide your temperature records and relevant medical history to the physician.
If further examinations are necessary and cannot be arranged in the outpatient setting, hospitalization for detailed investigation will be required.

Reply Date: 2007/03/10

More Info

Prolonged fever, especially one lasting for two months with temperatures ranging from 37°C to 38°C, can be a perplexing and concerning symptom. In your case, it appears that you've already taken the initial steps by consulting an infectious disease specialist and undergoing various tests, which returned mostly normal results. However, the persistence of your fever without a clear diagnosis warrants further evaluation.

Fever of unknown origin (FUO) is typically defined as a fever higher than 38.3°C (101°F) that lasts for more than three weeks without an identified cause after thorough investigation. The differential diagnosis for FUO is broad and can include infections, malignancies, autoimmune diseases, and even drug fevers. Given that your white blood cell count is within a normal range, it may suggest that a significant infectious process is less likely, but it does not rule it out entirely.

Here are some considerations and recommendations for your situation:
1. Further Evaluation: Since your fever has persisted for an extended period, it may be prudent to consider hospitalization for further evaluation. In a hospital setting, you can undergo more comprehensive testing, including imaging studies (like CT scans or MRIs), additional blood tests, and possibly biopsies if indicated. Hospitalization can also allow for close monitoring of your symptoms and response to any treatments that may be initiated.

2. Consultation with Specialists: If you haven't already, you might benefit from consultations with other specialists, such as a rheumatologist (to evaluate for autoimmune conditions) or a hematologist (to rule out blood disorders). Sometimes, a multidisciplinary approach can yield insights that a single specialty might miss.

3. Review of Medications and History: Consider reviewing any medications you are taking, as some drugs can cause fever as a side effect. Additionally, a thorough review of your medical history, including any recent travel, exposure to sick individuals, or other symptoms (like weight loss, night sweats, or changes in appetite), can provide clues to the underlying cause.

4. Monitoring Symptoms: Keep a detailed log of your symptoms, including the timing of fevers, associated symptoms (like chills, sweats, or fatigue), and any changes in your overall health. This information can be invaluable for your healthcare providers in determining the next steps.

5. Consider Non-Infectious Causes: While infections are a common cause of prolonged fever, non-infectious causes such as autoimmune diseases (like lupus or rheumatoid arthritis), malignancies (like lymphoma), or even endocrine disorders (like hyperthyroidism) should also be considered.

6. Patient Advocacy: If you feel that your concerns are not being adequately addressed, do not hesitate to advocate for yourself. Ask your healthcare providers about the rationale behind their recommendations and express your concerns about the ongoing fever. It is essential to have open communication with your medical team.

In conclusion, while it can be frustrating and concerning to experience prolonged fever without a clear diagnosis, there are steps you can take to further investigate the underlying cause. Hospitalization for comprehensive evaluation may be warranted, and consulting with various specialists can provide additional insights. Remember to keep track of your symptoms and communicate openly with your healthcare team to ensure that you receive the best possible care.

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