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The Informed Parent

Fever And Rash In A One-Year-Old That Is Not Roseola…But Due To A Vaccine We Gave

by Louis P. Theriot, M.D., F.A.A.P.
Published on Sep. 13, 2010

As I grabbed the chart of my next patient I was surprised to see Haley’s name. I had just seen her for the one-year-well visit, and she seemed to be doing just fine. Looking close at the chart the complaint given was fever and a rash, with suspected roseola.

Entering the room Haley’s mom smiled and said, “We’re back! Didn’t even make it two weeks.” Sure enough, her physical examination had been twelve days before and her growth, development and exam were textbook perfect. Mom went on to say that she was doing fine until two days ago when she seemed a little out of sorts, a bit fussy. There were no real symptoms. She didn’t have any vomiting or diarrhea. There were no cold symptoms and she actually had a good appetite.  Because she was cranky mom took her temperature and it was 100.8 degrees. It was decided to ride it out, but later the temperature went up to 101.6 degrees. With this, mom gave her Tylenol.

The following day things were much the same. The temperature went as high as 101.4 degrees but there were still no symptoms. That night, when Haley was given a bath, mom noticed a fine red rash on her face and upper body. It wasn’t raised or blistered like one would expect with chickenpox, and it didn’t look like hives. Most striking was how happy, playful and cheerful Haley was when the temperature would return to normal.

Mom went on to tell me, “That’s when I decided to do some research. So tell me if I am correct. I did an internet search, and have come to the conclusion that Haley has roseola. What do you think of my diagnosis?” she asked. Reading the look on my face she added, “Come on--fever, rash, one-year-old with no symptoms…it’s gotta be roseola!”

I commended her on the fine work and diligence, but told her that it couldn’t be roseola. As she started to appeal her case I showed her the chart and pointed to Haley’s vital signs. “She has a rash and a fever. Thus, by definition, it was not roseola.”

We discussed roseola in detail and I explained that it was caused by herpes virus 6. It is a common infection that almost all children get in early childhood. It was a good thought on her part because the peak age for roseola is 10-to-11 months. Most children have antibodies (protection) against this virus by four years of age, which means that they had to have had it before that time. Roseola causes a high fever, often as high as 104 - 105 degrees with virtually NO symptoms at all. The fever can last for as long as five days. It can be a bit unnerving because the child’s physical exam is usually normal. Quite often blood work and urine tests are done to try to locate the source of infection. These are invariably normal. The fever breaks suddenly and then the classic rash of roseola develops. The rash presents as small, red, flat spots on the face, trunk and extremities.

Roseola is unique in that by the time the fever breaks and the rash develops the child is happy and looks perfectly normal…with the exception of the rash. This timing of fever, followed by the rash is the hallmark of roseola and not seen in other illnesses.

With this Haley’s mom conceded that she didn’t have roseola. But then she asked what I thought she had. Pulling out the notes from the baby’s one-year-examination twelve days before I laid them on the table in front of us. I scrolled down the pages of notes pertaining to the visit. At the end I went slowly over the portion that described the immunizations she was to receive. Haley got her MMR, Varivax, Hib and Prevnar vaccines, which is standard for the one year visit. My finger rested on the line that described the MMR vaccine. Just then Haley’s mom let out a groan and shook her head. In the margin next to the MMR I had written that 4-to-6 percent of all infants who get the MMR will develop a fever and/or rash. But this may not occur until 5-to15 days AFTER the vaccine is given. “I distinctly remember you telling this to my husband and me. I am so mad at myself because when her fever reached over 102 degrees I didn’t even think of it. And I certainly didn’t think to look at your notes from her visit.”

Haley had one more day of fever. The rash faded away a day or two after that. She never developed any symptoms and was back to her usual happy self within 3-to-4 days. This is typical of the 4-to-6 percent of patients who develop the fever/or rash with the MMR vaccine. When I called Haley’s mom to follow up and see how she was doing, I told her I thought she did a remarkable job in her researching Haley’s complaints. She thanked me and then added, “Roseola was a good thought,” and I wholeheartedly agreed.

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