A previously healthy 40-year-old woman presented to a primary care clinic in New Orleans with a one-month history of fevers and a three-week history of swelling in her right armpit that had not abated with a course of trimethoprim-sulfamethoxazole (Bactrim, an antibiotic). On physical examination, there was tender lymphadenopathy (swollen lymph nodes) with overlying erythema (redness) in the right axilla (armpit) (see photo). A cluster of papules and a scar were noted on the distal (outer) right index finger, where the patient recalled being bitten by a stray kitten 2.5 months before presentation. Owing to concern for cat scratch disease (formerly known as cat scratch fever, thank you Ted Nugent), azithromycin was prescribed.
The fevers abated but the swollen lymph nodes persisted; therefore, further evaluation was performed. Ultrasound of the right axilla showed enlarged lymph nodes with an adjacent fluid collection. Polymerase-chain-reaction testing of a tissue specimen was positive for Bartonella henslae. IgG serologic testing for bartonella was also positive. A diagnosis of cat scratch disease was confirmed. Treatment with doxycycline and rifampin (both antibiotics) was given. Three weeks after initiation of treatment, the lymphadenopathy had worsened and the lymph nodes were leaking pus, so debridement (opening and cleaning of the wound) was performed. Three months after treatment, the symptoms had resolved.
Cat scratch disease is fairly common and, following interaction with a cat, often a young stray, symptoms start with redness and/or swelling and a small boil at the site of the cat scratch. This is often followed by generalized symptoms, such as fever, malaise, chills, aches and pain, and backache as well as non-painful swelling and redness at the local lymph nodes, either armpit or groin. The causative agent, as in this case, is the bacterium Bartonella henslae, found in the saliva of cats, especially young cats. While antibiotics will usually shorten the duration of symptoms, the disease is usually self-limited.
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