Disclosures: Brien reports no relevant financial disclosures.
November 20, 2020
4 min read

8-month-old boy presents with rash, thought to be MRSA infection

Disclosures: Brien reports no relevant financial disclosures.
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James H. Brien

An 8-month-old boy is brought to your clinic with a diaper rash. He had been seen a few days earlier in an urgent care clinic, where it was thought to be an infection with MRSA and treated with trimethoprim-sulfamethoxazole, or TMP-SMX.

This diagnosis was supported by a recent history of a minor skin infection on his arm with MRSA. However, he was brought to your clinic with the persistent rash and the development of some pain. On further history, the mother recalls that she thought there were a few small blisters present early on.

The patient’s past medical history is that of a healthy infant with no other problems, and his immunizations are up to date. His mother’s pregnancy, labor and vaginal delivery were normal with no complications or perinatal problems. His family history reveals that his father has frequent cold sores, with one recently treated and resolved with a 3-day course of valaciclovir. There have been no other sick contacts, and the patient does not attend day care.

His review of systems is positive only for the chief complaint. Specifically, his appetite and activity are normal, and the parents deny any recent episodes of diarrhea, past episodes of diaper rash or any other skin lesions or problems.

His exam is that of a healthy, happy and active baby with normal vital signs. The only positive finding is a rash about the penis and scrotum (Figures 1 and 2) showing some healing ulcerative lesions with some shallow, irregular-shaped erosions.

Figure 1. Upon examination, the patient had a rash about the penis and scrotum. Source: James H. Brien, DO.

Figure 2. Upon examination, the patient had a rash about the penis and scrotum. Source: James H. Brien, DO.

No lab tests are obtained in your clinic, but a culture done at the first visit to the urgent care clinic grew MRSA. However, the parents do not feel that there has been any improvement with the TMP-SMX that was prescribed, along with some over-the-counter topical diaper rash cream.


  • The patient is a healthy, 8-month-old, fully immunized male, with a diaper rash associated with a positive culture for MRSA.
  • Family history is positive only for the father, who had a recent cold sore; no other known sick contacts.
  • The rash appears resistant to TMP-SMX therapy and topical diaper rash cream.

What’s your next step?

A. Rx oral acyclovir
B. Full sepsis workup
C. Explore possible abuse
D. Choices A and C

The answer is D — begin acyclovir for cutaneous herpes simplex virus (HSV) infection and explore possible abuse. The diagnosis can be made with a high degree of confidence based on the history of vesicles and the appearance of ulcerative lesions alone if the examiner is familiar with the typical course and appearance of cutaneous HSV. If the patient had been seen earlier, typical vesicles would likely be seen, as shown on the face of the patient in Figure 3 who has classic HSV about the eye — another common location. However, if unsure, a herpes PCR can be performed from a sample of the lesion. In either case, lesions about the genitalia should be sampled for legal reasons in the event that abuse is possible. Acyclovir should be started as soon as the diagnosis of HSV is suspected, as early therapy results in more rapid resolution and limits further spread.

Figure 3. Vesicles around the eye caused by herpes simplex virus. Source: James H. Brien, DO.

In babies and young children with genital HSV infection, a review of red flags for abuse should be pursued, including eating and sleeping disorders, developmental delay, unusual sexual play and unusual fear of strangers. Additionally, in abusive parents, an angry response and poor cooperation, along with inconsistent or changing stories, are common and should prompt further investigation. To read more about these red flags, I would recommend the reference below (Ozyurt and colleagues). While the reference was written by child psychiatrists in Turkey, in many U.S. children’s hospitals, forensic pediatricians are tasked to investigate suspicious cases. It is imperative not to be accusatory but rather make parents understand the importance for them that the issue be properly cleared. A likely scenario might be that the father transferred the virus from his fingers during routine care, such as cleaning and diaper changing. Subsequently, there were no red flags or concerns found with this case.

A full sepsis workup (choice B) would be appropriate if the baby were younger than 2 months of age, to evaluate for disseminated herpes. At 8 months of age, this would not be routine but should be done if the baby were sick, appeared septic or had altered mental status.

Figure 4. Atypical Stevens-Johnson syndrome. Source: James H. Brien, DO.

Other unusual genital lesions might include atypical Stevens-Johnson syndrome, which can appear strikingly similar to cutaneous HSV (Figure 4). Stevens-Johnson syndrome was featured in the September 2014 issue of IDC for those who want to read more about it.

Figure 5. Significant swelling caused by a chigger bite (Eutrombicula alfreddugesi). Source: James H. Brien, DO.

Another common cause of children having genital lesions, especially in the summer months, include chigger bites — a blood-sucking mite (Eutrombicula alfreddugesi) that was featured in the July 2002 issue. There are no vesicles with the bite of this mite, only a very small mark with lots of swelling, which can be seen in Figure 5. In spite of what is pictured in that figure, urinary catheters are almost never needed. Contact dermatitis, such as that caused by poison ivy, can cause significant swelling with itching (Figure 6). An example of this can be seen in the July 2019 column. Occasionally, it can cause discrete lesions consisting of erythematous papules and/or vesicles (Figure 7). All these conditions are usually fairly easy to distinguish from herpes simplex lesions by a good history and physical.

Figure 6. Contact dermatitis can cause significant swelling with itching. Source: James H. Brien, DO.

Figure 7. Linear array of discrete lesions caused by streaking of poison ivy causing contact dermatitis. Source: James H. Brien, DO.

Columnist comments:

Please keep in touch and send along any interesting cases you may have seen with good pictures. Also, for the good of yourself, your family and your patients, stay safe by taking proper precautions while we are still dealing with this pandemic. Additionally, you should have had your annual influenza immunization by now. If not, GET IT SOON. The possibility of coinfection with influenza and COVID-19 could significantly increase the severity of the illness, as well as complicate therapy. While steroid therapy may be recommended for severe cases of COVID-19, that can actually prolong viral shedding of influenza, according to the CDC.


CDC. Testing and treatment of 2020-2021 seasonal influenza during the COVID-19 pandemic. Accessed November 9, 2020.

Ozyurt G, et al. Düünen Adam. 2015;doi:10.5350/DAJPN2015280411.