November 2007

An 11-year-old male from a small central Texas town was referred to the pediatric infectious diseases clinic for evaluation of a persistent sore on his right leg.

The history of the chief complaint began two months earlier when the patient injured the same area of his right leg.

The injury occurred as he ran through his back yard and tripped on a piece of heavy gauge wire, the kind used in cement jobs that happened to be sticking up out of the ground.

The wire punctured his right leg at the anterior, mid-tibia area. The injury initially healed without complication until some swelling was noted a few weeks later. The patient’s recollection was not precise. The mother also noted the swelling about three to four weeks after the injury; about the time it began to have some spontaneous drainage of a thin, yellowish material.

He was taken to a clinic to be evaluated, but a culture was not obtained, and treatment with double-strength trimethoprim/sulfamethoxazole (TMP/SMX) and doxycycline was begun for presumed methicillin-resistant Staphylococcus aureus (MRSA) cellulitis. He continued taking the antibiotics for 10 days without improvement.

As the intermittent drainage persisted, he returned for follow up and was given another 10-day course of TMP/SMX, because the mother admitted that he might not have complied with the directions given with the first course. During that visit, a sample of the drainage was obtained for Gram stain and culture. The stain showed no white blood cells or bacteria. Ten days later the culture became positive. He was then referred to surgery, where some granulomatous tissue was debrided and sent to the pediatric infectious disease clinic.

His past medical history was unremarkable. There had been no travel, camping or insect bites. His family and social history were unremarkable, with no one else in the family having had any similar problems. His immunizations were documented up to date. The only animal exposure was to the family cat, but he denied any close contact with the cat.

Examination revealed a healthy-appearing 11-year-old male in no acute distress. The only positive finding was the sore on his right leg (Figures 1, 2 & 3). As shown, it has an ulcerative appearance with a scant, blood-tinged discharge. There is some mild swelling about the sore, but minimal erythema beyond the raised rim of the lesion. Plain radiographs of the leg are shown in Figures 4 & 5, and were read as normal.

What’s Your Diagnosis?

1. Cutaneous leishmaniasis
2. Methicillin-resistant Staphylococcus aureus
3. Cat scratch disease
4. Mycobacterium fortuitum

Answer

The culture revealed the answer to be D, Mycobacterium fortuitum.

As mentioned at the beginning, this is a challenging case without knowing the results of the culture. But there are clues in the history, which was taken directly out of his chart, and examination, as shown in the figures. There is nothing diagnostic about the appearance of the lesion. It represents a chronic granulomatous, ulcerative skin lesion that might resemble many causes.

Cutaneous leishmaniasis may result in a similar ulcer, as shown in figure 6, a case I saw in the Middle East during the first Gulf War. You might have ruled it out by the fact that the child was from central Texas without recent travel, however, earlier this year, there were nine cases of cutaneous Leishmaniasis (Leishmania mexicana) identified in several communities around Dallas, Texas, none of whom had any travel to known endemic areas. While Dallas is not in central Texas, it is probably just a matter of time before similar cases are seen there as well. Prior to these cases, Leishmaniasis was endemic in this hemisphere only in southern Texas and points south. The agent is transmitted by the bite of the female sand fly, and may initially go unnoticed. The main clue in this case is that the sore on the patient presented began with an injury, not an insect bite.

The chronic draining sore of a node infected with Bartonella henselae (Cat scratch disease) can have a similar appearance. This usually happens as a result of performing a surgical incision and drainage of a suppurative cat scratch node, as shown in figure 7. Like with atypical mycobacteria, these lesions may drain for months. But again, the patient presented had an injury, not a cat scratch preceding the sore. Also, there was no adenopathy of the area that preceded the development of the sore, as one would expect in cat scratch disease.

There are several reasons MRSA would not be a choice. A draining MRSA abscess would not look like a granulomatous lesion. It would also not be a chronic sore. The pus draining is going to be continuous, not intermittent, opaque, yellow and usually copious, as shown in figure 8. A side note, my recommendation is not to use a combination of TMP/SMX and doxycycline for presumed MRSA. The only advantage would be in the event that the organism was resistant to one or the other, but not both. I believe a better option for empiric therapy for most cases of acute cellulitis/ abscess is oral clindamycin, which is also effective against group A strep, which may initially look the same. If you are seeing clindamycin resistance or inducible resistance in your community, then I would use one of these other options (provided the child is at least 8 years of age if using a tetracycline), and make sure a culture is done.

Back to the patient presented; Mycobacterium fortuitum is in the nontuberculous Mycobacteria category of “rapid growers.” They can often be recovered in as little as three to seven days and are frequently associated with wound and underlying bone infections, according to the 2006 Red Book. It appears to be fairly ubiquitous in the southeastern United States, all the way over to Texas, so that is where most cases are diagnosed and reported to the CDC. This particular strain was sensitive to clarithromycin, as well as all other drugs tested, although it was only intermediate to tetracycline. Therefore, he was treated with clarithromycin for two months, along with the surgical debridement, with a good outcome. Follow up 10 months later revealed no evidence of residual infection. This was a relatively minor infection with this organism. For the more severe infections, patients may require a combination of at least two drugs given IV in the initial stage of therapy, especially while awaiting sensitivities.

To read more about tuberculous or nontuberculous Mycobacterium infections, I would go to the Red Book for a quick reference or to anything written by Jeffrey R. Starke, MD, such as his chapter in Feigin and Cherry’s Textbook of Pediatric Infectious Diseases.

It may be my imagination, but I seem to be consulted on more uncultured or late-cultured infections nowadays than in decades past. It is my impression that physicians assume the cause of infections prematurely and have more confidence in our current antimicrobials than they should. We are also witnessing a reluctance in many surgeons to go after the cause in many infectious disease cases, such as abscesses of all types, infected bones and joints, ventriculo-peritoneal shunts, etc. I may be showing my age, but I can remember when us medical types had to bar the door to keep the surgeons from taking our patient’s to the operating room prematurely. Nowadays, it seems like we can’t “dynamite-em” into action. So, I think this is a shared problem between our medical and surgical colleagues alike. I can proudly say, “I have NEVER seen pus that I did not culture.” If this patient had been cultured at the first visit when there was drainage seen, the diagnosis would have been made much earlier, and earlier is always better.

Please keep in touch and have a Happy Thanksgiving. And please give a little extra thought (and maybe a care package) to our military personnel at this time of the year.