A previously healthy 40-year-old woman presented to a U.S. primary care clinic with complaints of a month-long fever and swelling in her right armpit that had persisted for three weeks, despite a course of trimethoprim-sulfamethoxazole. On examination, a non-indurated, enlarged lymph node was observed in the right axilla with overlying skin redness, and a scar surrounded by papules was noted on her right index finger. The patient recalled being bitten by a stray kitten two and a half months before admission. Suspecting cat scratch disease, she was prescribed azithromycin. Doctors Reena Wadhwa and Vilert Loving from the Ochsner Health System in New Orleans reported this case in The New England Journal of Medicine.
After the antibiotic course, the fever resolved, but the lymphadenopathy persisted. An ultrasound revealed an enlarged lymph node with an adjacent fluid collection. Core needle biopsy demonstrated caseous necrosis surrounded by histiocytes and granulomatous inflammation. PCR of the tissue sample and serum IgG testing were positive for Bartonella henselae. This confirmed the diagnosis of cat scratch disease (fe lignosis, Mollaret’s granuloma), a lymphogenously spread zoonotic infection transmitted by cats and, less commonly, dogs, monkeys, or guinea pigs. The patient was started on doxycycline and rifampin. Three weeks into treatment, the lymphadenopathy worsened, and purulent drainage began from the lymph node, prompting surgical debridement of the inflammatory focus. Three months after beginning therapy, all symptoms had completely resolved.
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