Cat scratch disease is an infection with the bacterium Bartonella henselae, passed to people through a scratch or bite from a cat, mostly kittens with fleas. It usually causes a small skin bump and then swollen, tender lymph nodes near the scratch, and most cases resolve on their own in weeks to months.
Key symptoms
- Small red bump or blister at the scratch site, 3 to 10 days after contact
- Tender, swollen lymph nodes 1 to 3 weeks later, often in the armpit or neck
- Low fever, fatigue and headache
- Red eye with a swollen node in front of the ear (Parinaud syndrome)
- Prolonged fever without a clear source in some children
What you find on exam
- Papule or scab at the scratch site
- Tender, enlarged nodes near the scratch, sometimes warm or draining
- Eye exam for conjunctivitis and vision; fundus for neuroretinitis
- Liver and spleen size
Tests
- Clinical diagnosis with cat contact and typical nodes
- Bartonella serology (IgG and IgM)
- PCR of node tissue or fluid if unclear
- Ultrasound of the node; biopsy if it keeps growing or cancer is a concern
Treatment basics
- Most cases need only supportive care: warm compresses and pain relief
- Azithromycin for 5 days to speed recovery of large nodes
- Needle drainage of a painful, fluctuant node; avoid cutting it open
- Longer combination antibiotics for eye, liver, spleen or bone disease
- Always treat immunocompromised patients, who can get bacillary angiomatosis
Red flags
- Sudden vision loss: neuroretinitis
- Confusion, seizures or coma: encephalopathy
- High fever with abdominal pain, or any infection in an immunocompromised patient
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.