Prolonged Fever of Unknown Origin

Question of the Week

Father taking child's temperature
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Q. My 7 year old son has had a fever for nearly 10 days now. The fever goes up to about 103.3 and back down to normal. At first my son was acting very healthy and normal, but the last couple of days he has been feeling very tired and worn out, and is coughing a lot. He was tested for strep a week ago and this came back positive, so he was put on antibiotics. However, the fever did not go away and although he now tests negative for strep, he is still sick. A blood count taken one day ago shows a "very healthy blood count" according to his pediatrician. Our son had the flu vaccine about one month ago.

At what point do we need to start getting worried and asking for more tests? It seems to me that 10 days is a very long time to have a fever, and our doctor is not being overly proactive about this. White Plains, NY

A. Having a child with a prolonged or persistent fever like this can be frustrating, both for a parent and their pediatrician.

On the one hand you don't want to overreact and put a child through a lot of unnecessary tests for what could be 'just a virus,' but then you also don't want to miss anything treatable or even more importantly, miss something very serious.

So doctors usually use a step-wise approach when managing a child like this.

Evaluating a Child with Prolonged Fever

If seen early in the illness, like within the first 3-5 days, they may just decide to observe a child after a full physical exam and depending on how well or sick your child seems. After that, your pediatrician will likely do more testing if the fever persists, like the strep test and blood count, depending on your child's other symptoms.

At this point, since your child still has a fever, he almost certainly needs to be seen again. This is especially important since you think he is getting worse. If your aren't comfortable seeing your pediatrician again, then consider getting a second opinion from another pediatrician or by going to the ER at a Children's Hospital.

Further testing might include a:

A detailed physical exam might provide further clues too, especially looking out for mouth ulcers, rashes, swollen lymph glands, or classic symptoms of pediatric diseases, like Kawasaki disease.

When evaluating a child with a fever of unknown origin (FUO), after several weeks, testing for less common things is also eventually done. This might include an abdominal sonogram or CT scan to look for a hidden abscess, stool cultures, an ANA (arthritis test), thyroid function tests, and antibody testing for other infections.

If all of that is normal, then testing for non-infectious causes of fever, like juvenile rheumatoid arthritis, malignancies, and inflammatory bowel disease, usually comes next.

Since your child is 'coughing a lot,' that might point to a respiratory illness as the cause of his fever, like a cold that turned into pneumonia or a sinus infection.

Walking pneumonia or mycoplasma pneumonia can cause a high fever, and may also be a possible cause of his symptoms. It is not unusual for this infection to last 1-3 weeks before a child starts to show improvement.

Again, since he isn't getting better, you should see a doctor again.

Clues to FUO Cause

To help your doctors narrow down what is causing your child's fever, consider the following questions:

  • Has he been around anyone else that has been sick?
  • Has he missed any of his routine vaccines? (your doctor might not think of vaccine-preventable diseases, figuring he should be vaccinated and protected against them)
  • Has he traveled out of the country recently? (Malaria)
  • Has he been around any farm animals or wild animals? (Brucellosis, Tularemia)
  • Do you have any pets? (reptiles - Salmonella infections, Birds - Psittacosis)
  • Has he been bitten by a tick? (Lyme Disease, Q Fever, Rocky Mountain Spotted Fever)
  • Has he been scratched by a kitten? (cat-scratch disease)
  • Has he eaten any raw or undercooked foods or drink unpasteurized milk or juice?
  • Does he have a heart murmur? (bacterial endocarditis)
  • Has he been taking any medications? (drug fever)
  • Does anything like this run in the family? (familial Mediterranean fever)
  • In addition to the fever, has he had other symptoms, like night sweats and weight loss? (lymphoma)
  • Has he had episodes like this before and were they associated with ulcers in his mouth? (PFAPA syndrome)

Again, keep in mind that since your child is 'coughing a lot,' he really doesn't haven't a fever of unknown origin, and he may just have some type of respiratory illness.

What To Know About FUO

In addition to these tips, other things to know about persistant fevers include that:

  • Fever of unknown origin has often been defined as having a fever for three weeks or more without a known reason after one week of doctors trying to figure out the cause of the fever.
     
  • A prolonged fever is simply one that lasts longer than usual, for example more than the seven to ten days that you would expect with a simple viral infection.
     
  • Antibiotics usually aren't prescribed just because a child has a fever that is lasting a long time. A specific cause should be determined cause.
     
  • In many cases, no specific cause of the fever is found and it just stops.
     

In addition to your pediatrician, a pediatric infectious disease specialist and a pediatric rheumatologist might be helpful if your child has a prolonged fever.

Sources:

American Academy of Pediatrics. Committee on Infectious Diseases. Red Book 2015.

Prolonged, Recurrent, and Periodic Fever Syndromes. Principles and Practice of Pediatric Infectious Diseases (Fourth Edition), Part II, 2012, Pages 117-127.

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