Review Question - QID 216564

This patient is presenting with constitutional symptoms (e.g., fever, tachycardia, hypotension, and chills) followed by the rapid development of buboes (lymph node inflammation) and comes from the southwestern part of the United States with likely exposure to fleas (animal sanctuary in New Mexico). This timeline of his symptomology and exposure history is most consistent with bubonic plague, which is caused by Yersinia pestis.

The bubonic plague is a deadly disease characterized by lymphatic system infection by Yersinia pestis. It is a gram-negative, intracellular, non-motile, facultative anaerobe. Rats and prairie dogs are reservoirs while fleas are the transmission vector for the pathogen. Outbreaks are known to occur in the Southwest USA. Disease progression begins within 1 week of an infected flea bite with the development of constitutional symptoms. Swelling secondary to lymph node inflammation known as buboes also manifest. Septicemic and pneumonic plague can develop if bacteria invade the bloodstream and lungs, respectively. With organ failure occurring in the late stage, symptoms such as hematemesis, gangrene, and coma can eventually be seen. Management involves supportive care and antibiotics (aminoglycosides are first-line).

Perry et al. performed a thorough review of Yersinia pestis. For the United States, squirrels (as opposed to rats) have been the most common source of the plague. They note that while the plague is not currently a prevalent disease in humans, the pathogen is widespread in different zoonotic loci. Given that it will not likely be eliminated, they recommend continued research into the disease.

Incorrect Answers:
Answer 1: Chlamydia trachomatis can cause lymphogranuloma venereum (LGV). Specifically, serovars L1-L3 are the culprit. LGV is a sexually transmitted disease characterized by the development of painless genital ulcers/papules and inguinal/femoral buboes. This patient did not develop any genital lesions and also developed axillary buboes. Doxycycline is the recommended treatment.

Answer 2: Pasteurella multocida causes pasteurellosis. It is commonly associated with a bite or scratch injury from cats or dogs. Patients can quickly present with signs of infection (erythema, edema, pain, etc.) at the injury site. Osteomyelitis can develop in more complicated cases. This patient did not express any injuries from animals and did not have any obvious skin injuries. First-line therapy is amoxicillin and clavulanic acid.

Answer 3: Sporothrix schenckii causes sporotrichosis. It occurs after inoculation of the fungus, most commonly through the skin. Hence, the disease is also known as "rose gardener" disease. It is classically characterized by ulcerated nodules involving local draining lymphatics. Despite the small wound on his hand, there are no other signs of ulceration along the lymphatic tract. Itraconazole is used for treatment.

Answer 4: Wuchereria bancrofti causes lymphatic filariasis. Following its transmission by mosquitoes, the proliferation of the parasite disrupts lymphatics. This pathogenesis leads to the classic association with lymphedema, which is not observed in this patient. Abnormal lymphatic drainage also leads to increased infection susceptibility. Triple therapy with ivermectin, albendazole, and diethylcarbamazine is recommended for treatment.

Bullet Summary:
Yersinia pestis causes bubonic plague, which is characterized by constitutional symptoms and the rapid development of buboes.