Most practitioners think that rashes and lesions of the fingers are relatively straightforward to diagnose and manage. But you will likely encounter some real “stumpers” in your lengthy careers that will produce much consternation and confusion. You must be willing to consider the unusual diagnosis, pathogen, or medication response. Each one of the following eight cases will hopefully teach some of the nuances about the pediatric “digital” world. Unless otherwise stated, each of the following cases was age-appropriately fully vaccinated and had a normal physical examination and vital signs.
This previously healthy 2-year-old white boy presented to your office with a painful blister on the lateral edge of the index fingertip within the past 24 hours (see Figure 1). The lesion is only slightly reddened at the base of the bullous lesion, which makes a herpetic whitlow less likely to be hiding underneath the bullous lesion. In addition, he has no history of or exposure to herpes simplex cold sores or lesions. It certainly appears to be a straightforward case of bullous impetigo — but is it? You decide to start empiric antibiotic therapy, but only after you have incised the lesion with a needle or blade and have also obtained a bacterial culture. When the lesion is unroofed, you do not observe any small circular fiery red herpetic-like lesions. However, you remember that for fingertip bullous lesions you must readjust your therapy specifically and accordingly. Why?
Figure 1. A 2-year-old white boy with painful pus-filled blister of the left index finger for the past 24 hours. Images courtesy of Stan L. Block, MD, FAAP.
A 12-year-old white girl presented to your office with both classic types of impetiginous lesions: the honey-crusted red-based round flat lesion of impetigo simplex proximally, and the early singular pus-filled blister of “bullous impetigo” distally (see Figure 2). You are aware that most impetigo sores — even the bullous lesions — are caused by Staphylococcus aureus. However, about 10% to 25% may be also caused by Streptococcus pyogenes, either as a sole pathogen but mostly as a co-pathogen. Similar to most US locales, you also have observed a 75% rate of methicillin-resistant S. aureus (MRSA) among the S. aureus skin lesions in your area. Thus, you will most likely opt for antibiotic coverage of MRSA in this case, instead of a cephalosporin that only has coverage for both S. pyogenes and methicillin-sensitive S. aureus.1 For outpatients, choosing coverage for MRSA means choosing between a very poorly palatable antibiotic (clindamycin) or an antibiotic with no S. pyogenes coverage (trimethoprim-sulfamethoxazole [TMP-SMX]). The latter choice will often require obtaining a bacterial culture of the lesion, in case the pathogen is S. pyogenes. With the clindamycin choice, you must also keep in mind that occasional strains of MRSA have developed resistance as well.1 Thus, careful follow-up, at least by phone contact, over the next few days may be prudent.
Figure 2. A 12-year-old white girl with a 3-day history of blisters on her right leg. The proximal lesion has burst, developing into typical impetigo, whereas the distal blister remains intact and is representative of the uncommonly observed bullous impetigo (similar to Figure 1).
A 10-year-old healthy boy presented to your office with this very painful, mildly reddened lesion of the proximal lateral nail (see Figure 3). You surmise that it is a commonly observed paronychia, most of which are caused by S. aureus, and in particular MRSA. Thus, you elect to treat this patient similar to the child with impetigo in Case 2.
Figure 3. A 10-year-old white boy presenting with a painful and reddened paronychia of the index…