September 2002

A 10-year-old girl presented to the clinic with a sore on her nose. She had first noticed it the day before when it was just a small bump. Upon awakening, it had become larger, with some blistering component and with a second lesion appearing nearby. She was unsure, but it may have started as an insect bite, as there was some initial itching. She also complained of some bumps that tended to reoccur on her lower extremities that had also flared up at this time. These extremity bumps had intermittently occurred for a couple of years with no itching or other sensations. They only bothered the parents. She had neither fever nor other complaints and was otherwise in good health. Her immunizations were up to date. There were no sick contacts and no one else at home had any rash or skin lesions. There had been no travel and she takes no medications. The only animal exposure is to a healthy family dog.

Examination revealed a blistering lesion on the tip of the nose and a new, similar-appearing lesion near the right nostril that is not blistering but had a cluster of small vesicles in the center (figures 1, 2). Examination of the rest of the skin revealed a rough-feeling papular rash on the extensor surface of the lower extremities (figure 3). There were also some similar lesions on the extensor surface of her upper extremities that she was unaware of having. As seen in figure 3, most of these lesions had a very small whitish dome on an erythematous base.

Part I. What’s the most likely cause of the nose lesions?

1. Staphylococcus aureus
2. Streptococcus pyogenes
3. Herpes simplex
4. Both A & C

Part II. What’s your diagnosis of the rash in figure 3?

1. Molluscum contagiosum
2. Staphylococcal folliculitis
3. Erythema toxicum
4. Keratosis pilaris

Answer

The answer to the first question is a little tricky without culture confirmation, but it is most likely due to herpes simplex virus (HSV) alone (C). The cluster of vesicles in the newer lesion is fairly consistent with HSV. And if these vesicles become confluent, the lesion can take on a blistering or bullous appearance. This can occur in a fairly short period of time (within two days of vesiculation). However, I have cultured both HSV and Staphylococcus aureus from a different patient with a similar lesion on his forehead (figure 4). In that patient, there appeared to be surrounding cellulitis that improved with antibiotic therapy, but the persistence of the vesicles prompted the HSV culture. The S. aureus recovered was assumed to be an epidermolytic toxin-producing strain causing the blistering that is seen. So if the progression of the lesion does not seem to be taking a typical course in appearance or duration, consider a mixed infection.

Part II

By coincidence, this patient also had a condition known as keratosis pilaris. This is a fairly common condition that appears to be the result of the formation of keratin plugs within the follicles, although the exact pathogenesis remains unclear. While it can occur anywhere, it tends to occur mostly on the extensor surfaces of the extremities, especially the upper arms. Some lesions may become inflamed. This condition can be found in patients from toddlers to middle age, and occasionally beyond. There also tends to be a family history in most patients. Reassurance and a skin moisturizer is usually all that’s needed for treatment. Some experts may recommend a keratolytic agent, but it will eventually resolve on its own.

Some may confuse keratosis pilaris with molluscum contagiosum (figure 5, from Jim Bass). However, molluscum lesions are larger, dome-shaped lesions that form as a result of infection with a poxvirus in the genus Molluscipoxvirus. Each lesion contains a core of whitish material that contains the virus. It is transmissible through direct contact or via fomites, and in some situations can be considered a sexually transmitted disease. Treatment can be by freezing with liquid nitrogen, electrocautery, mechanical removal or tincture of time.

Folliculitis is simply the inflammation of follicles. This may occur for a variety of reasons from a variety of organisms, but the appearance is the same: pustules on an erythematous base (figure 6). It is also usually self-limiting, but if associated with cellulitis, systemic antibiotics directed against staph are indicated. One should treat the underlying condition if known, such as microtrauma to the skin from rubbing of tight pants, etc.

Erythema toxicum is ruled out because of the age. This is a benign skin condition of unknown etiology of the newborn. It also appears like a vesicle or a pustule on an erythematous base that may be fairly discrete or broad. If the lesions occur in a cluster (figure 7), it could resemble HSV. They tend to occur within the first few days of life and are usually resolved by the second week. The contents of the lesions contain numerous eosinophils. Treatment is reassurance and to protect the baby from unnecessary testing.

There are numerous other skin conditions of children that could be included in this discussion if space allowed. But there are many books that do a much better job discussing these conditions than I can do. As usual, I recommend any pediatric dermatology book with Dr. William L. Weston’s name on it. Regarding these conditions, if it’s not in one of his books, you’ll probably never see it.

Closing Comment: Don’t forget, influenza and RSV season is coming soon. Now is the time to start identifying your high-risk patients for immunization and prophylaxis (respectively). Hopefully in the near future, the live, cold-adapted influenza nasal spray vaccine will be available, which will avoid the need for yet another stick. While you’re at it, you might also check to be sure your high-risk patients have had the pneumococcal vaccine as well as their other routine immunizations. They need every break they can get.