Teen with itchy feet and sores after mowing the lawn

What’s your diagnosis?

Be on the lookout for this common summertime problem.

James H. Brien, DO

A healthy, 17-year-old male seeks care of a sore right foot. He first noticed some small bumps with associated intense itching on both feet and ankles 4 days earlier after mowing his yard barefoot. This resulted in frequent scratching of both feet. His mother informed him that the pruritic bumps were caused by chigger bites, often referred to as “mower’s mites” and recommended that he take a swim in their pool, which she thought would kill the mites.

One day later, he developed an area of erythema with mild pain on the dorsum of his right foot. Two days later (the day of presentation), he sought care because of progression of the pain, swelling and erythema associated with the sores over the dorsum of his right foot (Figure 1, showing the area of concern on the right foot and the left foot and ankle for comparison, with multiple papular lesions on both feet and ankles, some of which appear to be scratched open). Figure 2 shows a closer view of the left foot and ankle, revealing numerous discrete lesions, again with evidence of being scratched with minimal inflammation. Figure 3 shows a closeup view of the right foot, revealing two large areas of bloody discharge on a large area of erythematous edema, with a lingering proximal papule nearby that is not involved within the area of concern.

Figure 1. Both ankles and feet showing numerous papular lesions and the swelling and erythema of the dorsome of the right foot. Image: James H. Brien, DO

Figure 2. Closeup of left foot and ankle. Image: James H. Brien, DO

Figure 3. Closeup of area of infection on dorsum of right foot. Image: James H. Brien, DO

What’s your diagnosis?

A. Mycobacterium marinum

B. Staphylococcus aureus

C. Streptococcus pyogenes

D. Vibrio vulnificus

Answer and discussion

The best answer is Staphylococcus aureus, which is by far the most common cause of soft tissue infections associated with injuries, including aggressive scratching. The reason for the scratching in this case was due to the intense itching associated with chigger bites. The proper name for this blood-sucking mite is Eutrombicula alfreddugesi, which is commonly found in grass and weeds in the warmer months. Unlike scabies, this mite takes a blood meal then leaves, whereas the scabies mite (Sarcoptes scabiei) will burrow into the skin, where it will live and lay eggs. They both result in such intense pruritus due to the digestive enzyme they secrete in the biting process that most people cannot resist scratching to the point of breaking the cutaneous barrier. While it is possible that almost any colonizing bacteria can take advantage of the broken cutaneous barrier to result in an infection with cellulitis, Staphylococcus aureus is by far the most common. The patient received 10 days of culture-directed oral therapy with good results.

Streptococcus pyogenes (group A streptococcus) soft tissue infections differ from S. aureus in some important ways, chiefly by possessing several virulence factors that move the infection along much faster, oftentimes with associated blistering and lymphangitis (Figure 4, a 3-year-old with group A streptococcus that started with minor, superficial injury). It is also more likely to result in necrosis of the tissue if not treated promptly. Many experts recommend using aggressive therapy with penicillin, as well as clindamycin (for its antitoxin effect). The case in Figure 4 can be seen in the September 2013 issue of Infectious Diseases in Children.

Figure 4. Group A streptococcus cellulitis, showing blistering and spread to the lymphatic channels up the leg. Image: James H. Brien, DO

The other choices, Mycobacterium marinum, a slow-growing nontuberculous mycobacteria; and Vibrio vulnificus, a gram-negative rod that lives in brackish or salt water, are both “water bugs” that can result in cutaneous infections via opportunistic injury that usually occurs while in a body of water containing either of these organisms. There is nothing unique about the appearance of the lesions caused by either of these organisms. However, in the case of Vibrio vulnificus, it may look similar to group A streptococcus lesions with blistering, and if the patient has an immune deficiency, the infection can rapidly progress to a life-threatening stage. It can also be acquired by eating uncooked, contaminated shellfish. In the case description above, the patient took a swim in their backyard pool, which, by the way, is not likely to help with resolution of the effects of chigger bites. Additionally, it would be extremely unlikely that either of these organisms would be found in a backyard pool, the vast majority of which are treated with chlorine. Also, it is a misinformed notion that swimming would get rid of the chiggers, which, as noted above, are on the skin long enough only to take a blood meal, then they leave.

Columnist comments

Vaccine hesitancy is again a front-page story with the measles outbreak that began in the southern plains of Texas in early March. To review the key features of the disease, I would refer you to my column from June 2019 at the link below:

https://www.healio.com/news/pediatrics/20190611/a-relevant-case-from-1989-a-12yearold-presents-with-fever-and-rash

That column presents a typical case of measles, and some others from a large outbreak we had in Texas in 1989. By the year 2000, measles was declared eradicated from the United States; not bad for the most contagious disease on earth. I am not going to state the obvious about the nonsense that has been repeatedly proven wrong regarding the safety and effectiveness of this vaccine, or the destructive and life-threatening potential of measles. I will just say, “Good luck and do the best you can in your practices.”