A 29-year-old woman with no significant past medical history presented with malaise, fever, headache, inguinal lymphadenopathy, and a painful lesion on her ankle (Figures 1 and 2). Other pertinent findings on cutaneous examination included faint blanching 2- to 3-mm macules on her trunk. There were no oral lesions and no signs of embolic phenomena. One week prior to presentation she had returned from a South African safari. All appropriate immunizations and prophylactic medications (i.e., antimalarial prophylaxis) were obtained before her trip.
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What is the diagnosis, and what is the treatment of choice?
DISCUSSION
This patient had an imported skin disease, most likely due to Rickettsia africae, that she contracted while in South Africa on safari (Table 1) (1). Rickettsiae are gram-negative coccobacillary bacteria that are strict intracellular parasites. Rickettsiae are most commonly associated with spotted fever infections (Table 2). In South Africa, TBF is commonly attributed to Rickettsia africae, R. conorii, and R. mongolotimonae (2). The disease is usually seen in white temporary workers or tourists (hunters and campers in rural areas) in endemic areas such as South Africa or the Mediterranean basin. The parasite, which lives in the salivary glands of arthropods, is introduced into the human host during a hematophagous tick bite. In South Africa, the most common tick vector for TBF is Amblyomma hebraeum. Rickettsiae introduced into the host at the inoculation site invade the endothelium, divide by binary fusion, and spread from cell to cell via the lymphatics to infect distant endothelial cells. In response, cytotoxic CD8+ T lymphocytes are directed against rickettsiae-infected endothelial cells. Acting in concert with the proinflammatory cytokines tumor necrosis factor alpha and interferon-gamma, these T lymphocytes are critical for clearing the host of the infection (3).
Clinical course
The incubation period for TBF is …
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