Common and Not-so-Common Rashes in Kids

Dermatology for Primary Care

Charles P. Vega, MD; Temitayo A. Ogunleye, MD


May 02, 2018

Clinicians see many skin conditions in the primary care setting. Medscape talked with a family physician, Charles P. Vega, MD, and a dermatologist, Temitayo A. Ogunleye, MD, to learn their thoughts about how to best diagnose and manage dermatology-related symptoms in primary care. This consultation is the fourth in a series addressing these common concerns.

Vega: Today, we are going to be talking about something quite relevant to primary care, but on which I think we can always can use a refresher: viral exanthems in children. It is also an important issue from a public health standpoint, because we're talking about infectious illness, some of which can be quite dangerous. And of course, we want to be aware of those.

I'll set the stage and then hand over to you, Tayo.

Ogunleye: Sounds great.

A Happy Toddler With a Rash

Vega: Our first case is an almost 1-year-old girl with intermittent fever to a temperature of 39.2°C for 4 days, responsive to antipyretics. Her only other symptom is clear rhinorrhea. Her fever abated yesterday. Today she has developed a light pink maculopapular rash that began on her chest, and is now also present on her neck and arms. Her past clinical history is essentially negative. Immunizations are up to date, with the exception that she has not yet had her 12-month well-child exam or immunizations.

Figure 1. Example of viral exanthem. Image from Medscape.

On physical exam, she is happy, nontoxic, and playing. Other than the rash, there are no other significant findings on exam. So, Tayo, just looking at that thumbnail of a case, what are you thinking?

Ogunleye: I think the two main things that I would think of are a viral exanthem or, if we're missing part of the history, a drug eruption. There are a couple of pieces of information that we would need to narrow down the differential diagnosis for a viral exanthem. One important factor is that she is well-appearing and playing. Another important factor that you described in the case is that she had a high fever the day before, and then the rash appeared. All of those things make me think of roseola as a possible diagnosis.

Vega: Roseola caused by human herpesvirus 6 tends to be more benign compared with the other major viral illness on the differential to consider, which is measles. Many of us may never have seen this vaccine-preventable illness, although with rising rates of vaccine refusals, we are now seeing outbreaks in the United States. Can you refresh us on how you distinguish between the two?

Ogunleye: The presentation in roseola classically is that a child with a high fever develops a rash after the fever abates. In general, these children are well-appearing, playing, and eating well. Other than their rhinorrhea and fever, they don't look ill.

In contrast, with measles, patients look more ill. Typically, the illness is present for about 3-4 days before the rash develops, and while patients still appear sick. With measles, in addition to fever, always keep in mind the three Cs: cough, conjunctivitis, and coryza (Figure 2). The rash usually begins on the face (Figure 3) and then moves down the neck and the rest of the body over the course of a few days.

Figure 2. Example of ill-appearing child with coryza and conjunctivitis. Image from Medscape.

Figure 3. Exanthematous eruption seen with measles. Image courtesy of DermNet NZ.

Vega: So the key is the general well-being of the child in question and the pattern of the fever, because that fever with measles will probably continue for at least a couple days after the rash, whereas usually in roseola, the fever is either very mild or gone by the time they present with their rash.

The other thing is always to do a good oropharyngeal exam, because Koplik spots, which are those gray-white papules—they might have an erythematous base—are pathognomonic for measles (Figure 4). If I find them, I am going to be very concerned about who else has been affected and talk to public health about those things.

Figure 4. Koplik spots. Image from Medscape.

Ogunleye: Exactly! The quality of the rash isn't necessarily specific, but the well-being of the child, timing of the fever, and other findings can be helpful.

The final condition that you could think of is rubella (Figure 5). On occasion, these children can have Forchheimer spots, which are nonspecific small petechiae on the soft palate/uvula. This finding is not pathognomonic for rubella, however. In general, rubella has a shorter course, and the rash appears more quickly. In traditional measles, you'll notice the rash appear during days 3-4, whereas in rubella, the rash will come on typically after the first day of symptoms.

Figure 5. Exanthematous eruption associated with rubella infection. Image courtesy of DermNet NZ.

Vega: You also indicated that a drug eruption should be considered. A history is paramount. In this case, the child's only medications have been antipyretics. But that is a good reminder to all of us that these presentations will not always have an infectious cause.

Continuing on the subject of viral exanthems, let's throw in one more twist. What if I were to add that this child also has some very bright red cheeks? That might change the way you think about this case quite a bit, right?

Ogunleye: Absolutely. The first thing you would consider with that description is erythema infectiosum, which we commonly refer to as "fifth disease." This is caused by parvovirus B19. These well-appearing kids present with a flat, bright red or rosy rash on the cheeks that lasts for about 1-3 days, followed by development of a lacy, reticular rash on their body (Figure 6).

Figure 6. Slapped cheek appearance (a) and reticular/lacy rash (b) associated with erythema infectiosum. Images courtesy of DermNet NZ.

Vega: On serology, about 1 in 5 children will be positive for parvovirus B19, although the rates of children developing that clinical picture are much lower. It usually occurs in the winter or spring. Fifth disease usually occurs in outbreaks. So if you see one child with erythema infectiosum, there's probably a lot more out there as well.


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