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A 10-year-old boy with a pruritic lesion
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A 10-year-old boy presented to his pediatrician in Abilene, Texas, with a mildly pruritic, erythematous lesion on his right leg, which was thought to be an insect bite, possibly that of a spider. It soon developed a vesiculo-pustular appearance with an erythematous base, and four days later, he noted a ring of erythema developing around the site. About a week later, the ring had spread, as shown in figure 1.
Further history revealed that the boy had been camping with friends about two weeks before his first visit. There were numerous insects, including ticks, seen during the camping trip. The patient recalled some itching in the same area of his right leg, which he scratched through his jeans, and did not think anymore about it. There was no tick seen at the site of itching, but he did remove one from his hair, and other campers removed several embedded ticks from themselves. There were numerous mosquito bites, as well.
Pediatric Infectious Disease, Scott and White's Children's Health Center and Associate Professor of Pediatrics,
Texas A&M University, College of Medicine, Temple, Texas.
e-mail: jhbrien@aol.com
The boy’s past medical history is unremarkable. His immunizations are up to date, and he has no other complaints. Except for the rash on his leg, his examination was otherwise normal, with normal vital signs.
No lab tests were done.
What’s your diagnosis?
- Babesia microti
- Borrelia recurrentis
- Rickettsia rickettsii
- Borrelia burgdorferi
Answer
Everyone knows that this is Lyme disease, so to make it more interesting, I thought I would ask for the cause.
The history and physical finding of a rash consistent with erythema migrans (EM) makes early localized Lyme disease, which is caused by Borrelia burgdorferi (choice D), the most likely diagnosis. The tick was apparently and unknowingly scratched off sometime after it had embedded and transmitted the organism.
Studies have shown that attachment must occur for at least 48 hours before the vector can transmit the organism. One might ask how a tick can be on a patient that long without being noticed. There are a couple of reasons: (1) the infecting tick is usually the nymphal form of the deer tick (Ixodes scapularis), which is very small and easy to go unnoticed. Even if the tick is completely engorged, it is smaller than the head of a straight pin and can be scratched off without notice; (2) if you know the natural behavior of boys on a camping trip, you know they are not likely to be spending time looking for ticks or notice if one is scratched off, certainly not if the tick is on a covered location, such as under his jeans.
The characteristic ring-shaped rash may be small or so large that it may be hard to recognize, as shown in figures 2 and 3, courtesy of Mike Weir, MD. The EM rash initially occurs at the site of the tick bite, usually within one to two weeks of the bite, but “satellite” lesions may later occur as a result of bacteremic spread to other skin sites. This is referred to as early-disseminated Lyme disease.
Other less common manifestations of early disseminated Lyme disease include cranial nerve palsies, particularly of the facial nerve (VII), as well as lymphocytic meningitis, conjunctivitis, joint and muscle pain and carditis. Late Lyme disease is usually manifested by recurrent arthritis and rarely neurologic manifestations.
Making the diagnosis
Diagnosis of early localized disease is usually clinical. Serology at this stage is likely to be negative, even if done in a reliable lab, and culture of a skin lesion is not usually available. Serology in those treated early in the infection may never develop detectable antibodies. Those who test positive on the screening tests should have the test confirmed by the Western blot technique, usually at a reference lab.
The patient above was treated empirically without serologic testing. The lesion progressed to develop a small necrotic center that healed without complication as the erythema resolved. The treatment of choice for a patient this age (10 years) with early-localized Lyme disease would be either doxycycline for those old enough or amoxicillin for two to three weeks. Second-line drugs would include cefuroxime or one of the macrolides. Treatment regimens for early disseminated and late disease depend on the manifestations. I would consult the references below for treatment details.
Borrelia recurrentis is one of the causative organisms of relapsing fever, which, as the name implies, results in recurrent febrile episodes, often accompanied by a variety of systemic symptoms mimicking influenza. Borrelia recurrentis is a louse-borne organism that does not occur in the United States but rather in various African countries, and it can have a high mortality rate among the weak and malnourished if untreated.
The initial febrile phase may last a few days to a week, followed by an afebrile period of variable duration, from days up to a few weeks. Subsequent febrile relapses are typically less severe and brief. The tick-borne relapsing fever that may be seen in this country is mostly caused by Borrelia hermsii. Diagnosis may be made visually in a thin or thick smear of blood or by serology. The spirochetes can be cultured from blood on special media, but this is seldom done due to its lack of sensitivity. Preferred treatment is tetracycline, erythromycin or penicillin.
Rocky Mountain spotted fever, the disease caused by Rickettsia rickettsii, is also a tick-borne disease that typically begins with fever, headache, myalgias and gastrointestinal symptoms and the “spotted” rash. The rash ranges from maculopapular to petechial, beginning on the wrists, hands, ankles and feet, then spreading toward the trunk. Diagnosis can be rapidly made with polymerase chain reaction of biopsy tissue from the rash, but this is not readily available. Culture of the organism is hazardous and not recommended. Therefore, diagnosis is usually made serologically with paired sera, but because of the lethal potential, one cannot wait for confirmation to treat. The treatment of choice is doxycycline, regardless of the patient’s age. Chloramphenicol is an alternate, if you can find it.
Babesiosis is the disease caused by Babesia microti, another tick-transmitted, intraerythrocytic protozoa. If clinically symptomatic, it produces a flu-like illness with fever and a variety of constitutional symptoms lasting several weeks. Diagnosis is made by showing the typical intraerythrocytic tetrad-appearing protozoa on a blood smear, as shown in figure 4, sometimes by serendipity. The recommended treatment is with clindamycin plus quinine or atovaquone plus azithromycin for 10 days.
Dr. Brien’s commentary
Last month, I mentioned that James Shira, Colonel, Medical Corps, U.S. Army (retired) (figure 5) is a candidate for president-elect of the AAP. You might ask, “why would I suddenly become politically active with the Academy and single out this outstanding pediatrician for special commentary?” Well, since you asked, I’ll tell you; in 1977, I won one of the very competitive spots in the PL-1 class at Fitzsimons Army Medical Center in Denver.
I know it may be hard for many of you to believe, but I was not the brightest penny in the bank, and by the fall, academic weaknesses began to show. Jim Shira was my department chief (chair) and program director. He could have dropped the hammer and gotten me out with the certainty of picking up an off-cycle resident in December of 1977. But instead, he devised a plan of remediation with the help of my chief resident, Jim Bowen (now a child psychiatrist in Flagstaff, Ariz.), to get me up to speed. Through COL Shira’s leadership, I overcame many of my weaknesses (there’s always some left) and graduated from the residency two and a half years later. When COL Shira retired from the Army Medical Corps, he went on to have a highly successful second career at The Denver Children’s Hospital, where he became chair of the department of pediatrics.
Why mention this embarrassing, and thankfully short, chapter in my life? You can easily read all about the medical missionary activities and awards Dr. Shira has received and important positions he has held, both within the Academy and elsewhere, in the material provided by the Academy at www.aap.org. However, that information cannot reflect the intangible qualities that make Jim a perfect candidate for this important position.
Many people have held leadership positions that are not good leaders. They are what I call “professional leaders;” those who seek positions for reasons other than serving and representing their organization and/or subordinates.
A few gifted people are excellent leaders who seem to naturally posses this intangible quality to which I am referring. As I personally learned very early in my career (30 years ago), Jim Shira is one of those “natural” leaders. I know there are those of you who are politically active and others who run in the other direction. I consider myself somewhere in the middle; not really interested in holding office, but we should all recognize the important value of the Academy in promoting child health care and professional development.
COL Shira has a natural ability to lead this organization and the compassion needed to completely dedicate himself to this noble cause. So, even if you are not active politically, I encourage you to just take a few minutes this summer to get involved, learn about the candidates and vote. Voting begins online on Friday, Aug. 31, and ends at 2 PM Central Time, on Monday, Oct. 1. I am still not the shiniest penny in the bank, but much of what I am, Jim Shira made me. Plus, the bankers do not seem to mind much.
By the time this issue comes out, I will have returned from a medical CME trip to northern Iraq (Erbil, Kurdistan), where a small group of us infectious disease types will be teaching a three-day Hospital Infection Control Course to Iraqi physicians. Hopefully I will have some pictures to share and perhaps an interesting case or two to show in the subsequent issue(s).
I would like to thank Jay Capra, MD, a former Scott & White pediatric resident, for contributing this interesting case of Lyme disease, which we do not often see in the central Texas area. Jay is proudly pictured with his family in figure 6 at his son’s recent graduation from Marine Corps Boot Camp in San Diego.
For more information:
- 2006 AAP Red Book
- Anything written by Eugene Shapiro, MD.
What’s Your Diagnosis? is a monthly case study featured in Infectious Diseases in Children, with treatment information and discussion to follow.