Persistent Low-Grade Fever: Possible Causes and Next Steps for Evaluation

Persistent elevated body temperature?

Hello, doctor.
Last August, I had a fever reaching 38 degrees Celsius (ear temperature), which dropped to 37.7 degrees on the same day.
However, I have been experiencing a persistent low-grade fever ranging from 37 to 37.5 degrees until March of this year.
In March, I had two instances of fever reaching 37.8 to 38 degrees.
I visited the hospital in October last year and underwent various examinations across different departments, all of which returned normal results.
Today in March, I went to the hematology-oncology department, and the doctor also said my blood tests were normal.
I am currently entering menopause, and I initially thought this might be the cause.
However, I consulted three obstetricians and gynecologists, and they all stated that hot flashes do not cause fever.
I am not experiencing hot flashes; instead, I have a continuous low-grade fever.
When my temperature is elevated, I feel a bit uncomfortable in my ears.
The prolonged low-grade fever has led to feelings of depression, anxiety, and palpitations.
I would like to ask the doctor what factors might be causing my consistently elevated body temperature.
I have already undergone examinations in various departments; where else can I look for the cause? (My normal baseline body temperature used to be 36.4 to 36.5 degrees.) Thank you, doctor.

Xiao Cai, 50~59 year old female. Ask Date: 2024/04/28

Dr. Chen Bozhang reply Family Medicine

Dear Ms.
Tsai,
I understand from your letter that you have been experiencing persistent low-grade fever since August of last year, and various examinations have not revealed a cause.
Generally, the potential causes of continuous fever may include infections, rheumatologic and autoimmune diseases, hematologic malignancies, and central nervous system disorders.
Have you consulted with specialists in infectious diseases or rheumatology and immunology for evaluation? Uncommon infections and rheumatologic diseases are often potential causes of fever of unknown origin.
If you have already been evaluated by these two specialties as well as hematology and oncology, the next step would be to consult a neurologist to assess whether there could be a central nervous system-related cause for your chronic fever.

Reply Date: 2024/04/28

More Info

Persistent low-grade fever can be a perplexing and frustrating symptom for many patients, especially when extensive evaluations yield no clear diagnosis. In your case, the history of low-grade fever persisting from last August until now, along with the normal results from various specialists, raises several considerations.

First, it’s important to define what constitutes a low-grade fever. Typically, a body temperature between 37.2°C (99°F) and 38.3°C (100.9°F) is classified as low-grade fever. Your reported temperatures of 37-37.5°C fall within this range, indicating that while you are not experiencing a high fever, the persistent elevation is noteworthy.

There are several potential causes for persistent low-grade fever, and they can be broadly categorized into infectious, inflammatory, neoplastic, and other miscellaneous causes:
1. Infectious Causes: Chronic infections, such as tuberculosis or certain viral infections, can lead to prolonged low-grade fever. Even if initial tests are negative, some infections may require more specific testing or imaging studies to diagnose.

2. Autoimmune Disorders: Conditions like systemic lupus erythematosus (SLE) or rheumatoid arthritis can present with persistent low-grade fever. These conditions may not always show abnormal results in routine blood tests, especially in the early stages or during periods of remission.

3. Endocrine Disorders: Thyroid dysfunction, particularly hyperthyroidism, can cause an increase in body temperature. Given that you are entering menopause, hormonal fluctuations could also be contributing to your symptoms, although you mentioned that several gynecologists ruled out hot flashes as a cause.

4. Malignancies: Certain cancers can present with persistent low-grade fever. While your hematology tests were normal, it may be worth discussing with your doctor if further imaging studies (like a CT scan or PET scan) are warranted to rule out any underlying malignancy.

5. Psychogenic Factors: Chronic low-grade fever can also be associated with psychological conditions such as anxiety and depression, which you mentioned experiencing. Stress and anxiety can manifest physically, and it’s possible that your emotional state may be contributing to your perception of fever.

6. Miscellaneous Causes: Other factors such as medications (drug fever), environmental factors, or even lifestyle choices (like diet and exercise) can influence body temperature.

Given the complexity of your situation, here are some steps you might consider taking next:
- Revisit Your Primary Care Physician: It may be beneficial to have a comprehensive review of your symptoms, medical history, and any treatments you have undergone. A fresh perspective might lead to new insights.

- Consider a Rheumatology Consultation: If autoimmune disorders are suspected, a rheumatologist can perform more specialized tests and assessments that may not have been done previously.

- Thyroid Function Tests: If not already done, checking your thyroid hormone levels (TSH, Free T4, and Free T3) could help rule out thyroid dysfunction.

- Infectious Disease Evaluation: If there is any suspicion of a chronic infection, a referral to an infectious disease specialist might be warranted for further evaluation.

- Mental Health Support: Given the impact of your symptoms on your mental health, seeking support from a mental health professional could be beneficial. They can help you manage anxiety and depression, which may in turn alleviate some of your physical symptoms.

- Lifestyle Modifications: Ensure you are maintaining a balanced diet, regular exercise, and adequate hydration. Sometimes, simple lifestyle changes can have a significant impact on overall well-being.

In conclusion, persistent low-grade fever can arise from a variety of causes, and it often requires a multidisciplinary approach for proper diagnosis and management. Continue to advocate for your health, and don’t hesitate to seek further evaluations until you find the answers you need.

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