Viral exanthems: what this microbiologist didn’t know about rashes

I’m a microbiologist by training, and I have developed a pretty strong interest in pathogenesis. But I am NOT a clinician. So when a rash appeared on Monkey’s forehead and torso yesterday afternoon, a couple of days after his fever and cold had begun to clear up, I completely. Freaked. OUT.

Thank God I work with doctors, and infectious disease specialists at that. These people have become my sanity check when it comes to stuffy noses, fevers, diarrhea – and now rashes. After a lengthy discussion with one of my favorite pediatricians, we pseudo-diagnosed Monkey, putting my mind at ease and saving Hubby and I another trip to the pediatrician. Before I share the diagnosis, however, I thought I’d impart my recently acquired knowledge on viral exanthems (a fancy-schmancy doctor word for rashes).

First, a disclaimer: please, oh please, keep in mind I am not a pediatrician. My doctorate is a PhD, not an MD. Do not use this post as a diagnostic tool; it is merely intended to help you along in a conversation with your family doctor, or provide you with some interesting trivia for your next dinner party (‘cuz who doesn’t like a nice dinnertime discussion on rashes?)

Alright, disclaimer aside, I’m going to tell you a little bit about three of the most common infections associated with rashes in children around Monkey’s age or older. Each of these infections is caused by a virus (another reason I shouldn’t be considered an expert in this area), so they cannot be treated with antibiotics. In each case, the rashes appear as the fever breaks and are caused by the immune reaction to the virus, so the child is most contagious prior to the appearance of the rash.

1. Fifth disease.Caused by human parvovirus, fifth disease is most common in school-age children during late winter and spring time. Symptoms include a mild fever (<102 °F), sore throat, and rash. As the fever subsides, the rash begins on the face, with bright red cheeks as if the face has been slapped, then spreads to the trunk, arms and legs, forming a lacey pattern. The rash may or may not itch. Additional note for pregnant mothers: fifth disease can cause problems for babies in utero, so if your child exhibits these symptoms and you’re pregnant, get yourself to the OB right away to check on your immune status.

Fifth disease rash. Click image for source.

2. Roseola: Caused by one of two human herpesviruses (HHV-6 and HHV-7), infection occurs throughout the year in infants and toddlers. Symptoms include irritability, swelling of the eyes, and a very high, sudden fever (>102 °F), followed by the development of pink non-itchy rash with raised or flat lesions on the trunk, arms and legs. Because of the high fever, febrile seizures can occur but are not common.

Roseola rash. Click image for source.

3. Hand, foot, and mouth disease (HFMD). Not to be confused with foot and mouth disease, which occurs in livestock, HFMD can be caused by one of many different enteroviruses, most commonly Coxsackie A and Enterovirus-71. Symptoms are variable due to diversity among the enteroviruses, but can include moderate fever, malaise, vomiting, sore throat, general cold-like symptoms, diarrhea, loss of appetite, and raised lesions on the hands, feet and mouth (hence the name). As the fever reduces, a pink non-itchy rash may also appear on the body and head. Perhaps the most notable trademark of HFMD is its prevalence in daycares and early school-age children during the summer and early fall. The viruses that cause HFMD can also cause cold-like symptoms and aseptic meningitis (with very bad headaches) in adults.

Raised lesions on the mouth from HFMD. Click image for source

Raised lesions on the hands from HFMD. Click image for source.

Body rash proceeding fever with HFMD. Click image for source.

So here’s a case study for all you wannabe clinicians. Monkey began experiencing a runny nose and mild cough last week, and became especially fussy as the weekend inched closer. By Saturday evening, he had a very mild fever (~100 °F), was VERY fussy, constantly wanted to be held by mama or dada, and would lay his head on the floor of his nursery while trying to play (seriously pathetic to watch). Motrin helped his fussiness some, mainly by helping him fall asleep. By late Sunday night, Monkey’s fever had risen to ~102 °F, and he had snot constantly pouring out of his nose. He had a few lose stools on Sunday and Monday, but only one that I would have characterized as diarrhea.

Monday was Monkey’s 9-month check-up, so we got a complete look-over from the pediatrician. His weight was lower than expected, but it was assumed this was possibly due to him recently starting table foods (only a small portion of food actually makes it to his mouth right now, but his coordination is slowly improving) and mama’s milk supply taking a hit due to travel and stress from job interviews. Monkey’s ears were clear, but he had a very red throat. I was starting to come down with a stuffy nose and slight cough, very common after I travel, so we all assumed this was just a little cold virus making its way through the Dr. O family. By Monday evening, Monkey’s fever was all but gone, and Tuesday morning, Hubby and I woke up to a perfectly happy baby boy. He returned to daycare Wednesday, fever free. Wednesday afternoon, I noticed a rash all over his head and body when I picked him up from daycare. I proceeded to freak out, microbiologist mama style, and called the help line at our local children’s hospital.

Today I’m feeling much better, as is Monkey, although he still has a rash lingering on his legs, arms and cheeks this morning. So what do you think Monkey had/has? Leave your probing questions and diagnoses in the comments!

Our diagnosis is here. Let me know if you think we’re way off base. 😉

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15 thoughts on “Viral exanthems: what this microbiologist didn’t know about rashes

  1. What is it about rashes that makes us FREAK OUT??!!

    I would say Fifth disease…but I’m no clinician either. Just another mama who equally freaks out where rashes are concerned 🙂

    Hope your job interviews are going well.

  2. My mom wondered the same thing when I mentioned the rash yesterday morning, so that was one of the first questions I asked around here. GAS (Group A Strep) is actually very rare in infants, but it does occur. However, the rash for GAS is very distinctive (click for picture) and feels like sandpaper. Monkey’s rash was light pink, more speckled, and completely flat – I couldn’t feel anything on his skin. Additionally, the scarlet fever rash generally appears with the symptoms, as it’s caused by an exotoxin that the bacteria makes, whereas Monkey’s rash appeared a day or two after he started getting better.

    Good guess – but no dice 🙂

  3. his fever didn’t seem high enough for Roseola, and the kiddos I’ve know that had it got the rash pretty quickly after the fever broke. Sounds more like Fifth’s disease from what you put in the post, but I’ve not been around it before. From what I understand, hand foot and mouth is highly contagious and my friends said it made for a REALLY miserable baby that refused to eat, or nurse, for days because his mouth hurt. If monkey just has a red throat but not sores then I would count it out.
    My kiddo had all sorts of rashes as a baby. Although some were from allergic reactions, others were just a mystery.

    I really want to know more about the job interview stuff. I’m glad to hear they are going well though!

  4. ok, even though the fever only got to 102, I still think it was Roseola. just about every case I’ve heard of where a kid was miserable for a few days then got a rash has been roseola, so that’s my final answer 🙂

  5. I thought it was fairly common for kids to get rashes after a viral infection, especially if they had a fever (so says my pediatrician). My oldest son didn’t, but my middle son does. It freaked me out the first time around, but not any more. As I understand it, it need not be the virus that itself causes a rash; the rash is more like an allergic reaction (my middle son has multiple food allergies so he’s prone to hives I would say), i.e. a systemic after-the-fact reaction to the virus. (Obviously, this is my layperson understanding).

  6. My kids have gotten all three of the rashes that you mentioned above (Hoo-ray for, daycare!)

    Before I give my opinion, some quick questions. how is Monkey acting? Does he seem normal other than the rash? Is he scratching the rash (Does it itch)? Are his stools still loose?

  7. That was basically what the doctor’s office and hospital help line nurses told me, too. It’s mostly true, but somewhat simplified. Not all fevers or viral infections result in a rash (adenovirus, which causes sore throats, for example). The rashes resulting from infection with different viruses vary as well. So there’s something specific about how the immune response reacts to each of the above viruses, resulting in the rash. Other viruses cause a rash themselves (measles and mumps), and some cause none.

  8. No itchiness, and he was feeling absolutely fine by the time the rash appeared. Prior to the rash, he was extremely inactive, would lay down anywhere if we didn’t pick him up, and cried this horrible cry when the motrin wore off…like I haven’t heard him cry since he was a colicky newborn. Very sad:(

  9. So the diagnosis was (drumroll, please) – hand, foot, and mouth disease. Although Monkey never had the rash on his hands or feet or in his mouth, he displayed all the other “textbook” symptoms, including the diarrhea and general cold-like symptoms (aside from the sore throat). The post-fever rash also looked more like HFMD than fifths disease or roseola. In addition, mama and dada have had horrible summer colds since Monkey got sick, a trademark of what adults go through with enterovirus. The biggest reason for the diagnosis, however, was that our region is experiencing a HUGE outbreak of HFMD right now.

    It’s a guess of course, and without some sort of diagnostic test (PCR is the preferred option these days) to use on Monkey’s snot, it’s going to have to stay a guess. Hubby promised me we get a booger sample next time Monkey gets sick…what a good Hubby. 🙂

  10. Honestly, I now know why I’m not a diagnostician. I was totally thinking along the lines of 5th disease, especially since he seemed to be acting normal and didn’t have the rash on his hands/mouth. Glad every one is doing better!

  11. When my kid had HFM disease he never got a rash, just pretty prominent white pustules in the back of his throat, which is how the pediatrician diagnosed it in 10 seconds. He also had really high fever for nearly 5 days and was really miserable…
    Poor Monkey.

  12. Like you I am a microbiologist by training, and just returned from a trip to the pediatrician for the same reason. My baby woke up with a rash on his trunk, after one week of fever and a lab confirmed diagnosis of adenovirus. The doctor used the exact same terminology viral exanthem due to adenovirus infection. Baby had been miserable for a while, but was very happy having stopped having a fever and diarrhea. The rash seems to not bother him at all.

  13. I am curious as your picture of the rash and almost identical story as my almost 2 year old, how long did the rash part stay? Her rash didn’t appear until after her fever was gone and was feeling/acting normal again. But it has been just over 2 weeks and the rash is still everywhere and seems to be spreading. Thinking I should return to the dr???

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