Toddler develops pustular lesions on right hand following stinging pain
What’s your diagnosis?
Click Here to Manage Email Alerts
A 3-year-old girl came running into her house, crying loudly with pain in her right hand.
Her mother noticed several flat red marks, but no break in the skin, and she assumed they were insect bites or stings. She applied some calamine lotion and gave her a cookie. The stinging eventually stopped, and the child stayed in the house the rest of the day. The next morning, the red spots developed into relatively painless pustular lesions, with a mild pruritic component. Out of concern for infection, the mother took the child to the primary care provider, who found her to be a healthy 3-year-old with several pustular lesions on her right hand (Figure 1).
What’s your diagnosis?
A. Blistering dactylitis
B. Solenopsis invicta stings
C. Herpetic whitlow
D. Polistes apachus stings
Answer and discussion
This is a case of stings by the fire ant, or Solenopsis invicta (choice B). We should be glad these insects are small, otherwise they might well dominate the world. Few things in nature can defeat these small warriors. However, a commercial poison that comes as a bait (Amdro for example) can eradicate a fire ant mound.
If their mound is disturbed, they will immediately come after the source en masse (Figures 2 and 3).
Because my assistant got scared and ran home, I had to finish an experiment by myself that showed that fire ants were able to reach 12 inches from their mound within 30 seconds, as shown using a sheet of paper taped to a yardstick (Figure 4).
When these ants get on you, they immediately sting repeatedly, often resulting in two to three stings at the same site, causing most children to go running home (like my assistant). The sting sites are very painful, leaving erythematous marks at first, which then become papular. By the next day, a pustule has formed (again, see Figure 1) with mild pruritus, tempting the provider to treat with an anti-staph antibiotic, but it is not needed. These are usually “hot stovetop” moments that teach people to stay away from fire ants. The insects tend to live in the Southern states but are creeping north, especially with climate change.
Blistering distal dactylitis refers to a discrete blister on the tip of the finger (Figure 5) and is almost always caused by group A strep. I usually sterilely prick the blister to drain the fluid and culture it, and then I treat with a short course of oral antibiotic, like any other group A strep infection (unless it comes back positive for Staphylococcus aureus).
A herpetic whitlow can have discrete pustules or larger blister-like lesions, where multiple vesicles and pustules have coalesced. Classically, the sore is on the tip of the finger but can be found anywhere along the finger or the hand (Figure 6).
Polistes apachus is the genus and species of the common yellow wasp, AKA paper wasp (Figures 7 and 8).
These creatures will also attack from the air en masse if their paper-like nest is disturbed. Unlike bees but like the fire ant, these wasps can sting multiple times each.
The sting will result in immediate pain, with diffuse swelling within minutes (Figure 9).
Common analgesics and a cookie will usually get things back to normal. Figure 10 shows the reflex exposure of the stinger in a wasp dead from insect spray.
Columnist comments
Since we are in the summer now, keep a lookout on your property for fire ant mounds and wasp nests, often found in the overhanging eves of roofs or other structures that give protection from the rain. When seen, teach your children to stay clear of them. Otherwise, they may learn the hard way, like touching a hot stovetop.
For more information:
Brien is a member of the Healio Pediatrics Peer Perspective Board and an adjunct professor of pediatric infectious diseases at McLane Children's Hospital, Baylor Scott & White Health, in Temple, Texas. He can be reached at jhbrien@aol.com.