A 25-year-old woman comes to the office due to a small ulcer on the right upper thigh. She went camping yesterday and while she was putting her pants on she suddenly had a feeling of being bitten over her right upper thigh. She ignored it, but the pain has been increasing. She has had no abdominal pain or difficulty breathing. The patient has no medical problems and takes no medications. Temperature is 36.8 C (98.2 F), blood pressure is 116/72 mm Hg, and pulse is 74/min. Physical examination shows an erythematous and painful ulcer on the lateral aspect of the right upper thigh; the remainder of the examination is unremarkable. Which of the following complications is most likely to develop in this patient over the next few days?

Question

A 25-year-old woman comes to the office due to a small ulcer on the right upper thigh.  She went camping yesterday and while she was putting her pants on she suddenly had a feeling of being bitten over her right upper thigh.  She ignored it, but the pain has been increasing.  She has had no abdominal pain or difficulty breathing.  The patient has no medical problems and takes no medications.  Temperature is 36.8 C (98.2 F), blood pressure is 116/72 mm Hg, and pulse is 74/min.  Physical examination shows an erythematous and painful ulcer on the lateral aspect of the right upper thigh; the remainder of the examination is unremarkable.  Which of the following complications is most likely to develop in this patient over the next few days?

Quizplus · Accepted Answer

This patient's clinical presentation, with a small ulcer developing at the site of a recent bite, is highly suggestive of a brown recluse spider bite. Such bites commonly occur as patients are putting their clothes on. They are often painless and may initially go unrecognized, but some bites are painful or cause a burning sensation. Many cases result in a small papule that heals in days to weeks. However, in some cases, a deep skin ulcer develops at the bite site over the course of a few days, with an erythematous halo and a necrotic center that can progress to an eschar. With basic wound management, the lesion often heals without scarring. Debridement should be avoided in the early stages of necrosis but may facilitate healing once the lesion is stable and well-demarcated; severe cases may require skin grafting. (Choice A) By contrast to brown recluse spider bites, black widow spider bites often lead to more pronounced local and systemic manifestations due to effects of the toxin. These include muscle pain (a prominent finding), abdominal rigidity (sometimes mimicking a surgical abdomen), and muscle cramps (seen in >60% of patients). Wound ulceration is uncommon, and patients commonly develop nausea and vomiting within hours of the bite, making this an unlikely diagnosis in this patient. (Choice B) Arthritis, arrhythmias, and facial palsy can occur as late complications of Lyme disease; these typically do not develop until months after the tick bite. The initial rash, erythema migrans, is classically a target lesion with central clearing (not ulceration) at the site of tick bite. The tick must remain attached for ~48 hours before transmission occurs. (Choices C and D) Hemoglobinuria, bleeding, and muscle paralysis may be seen with snakebites, which would cause severe local pain, swelling, and discoloration within hours of the bite. Educational objective: Brown recluse spider bites can cause a deep necrotic ulcer at the bite site. The ulcer can progress over days to an eschar.

A 25-Year-Old Woman Comes to the Office Due to a Small