# Treatment-Resistant Femoral Lymph Node Abscess Caused by Cat Scratch Disease: A Case Confirmed by Polymerase Chain Reaction

## TL;DR

A child with a rare, treatment-resistant lymph node abscess caused by cat scratch disease was diagnosed using PCR, showing the value of molecular testing in unusual cases.

## Contribution

Demonstrates the clinical utility of PCR for diagnosing atypical cat scratch disease cases when traditional methods are inconclusive.

## Key findings

- PCR confirmed Bartonella henselae DNA in lymph node tissue, aspirate, and serum samples.
- Empirical therapy and serology failed to provide a definitive diagnosis.
- Molecular diagnostics improved diagnostic accuracy and avoided unnecessary procedures.

## Abstract

Cat scratch disease (CSD), a zoonosis caused by Bartonella henselae, frequently presents as localized lymph node swelling near sites of inoculation, such as scratches or bites. Here, we report a rare pediatric case of CSD in an eight-year-old girl, manifesting as a treatment-resistant femoral lymph node abscess. The patient had a history of chronic exposure to domestic cats. Initial empirical therapy was ineffective, and serology alone was inconclusive. A definitive diagnosis was established by detecting B. henselae DNA using polymerase chain reaction (PCR) from lymph node tissue, aspirate, and serum samples obtained during incision and drainage. This case highlights the clinical utility of molecular diagnostic techniques, such as PCR, in atypical CSD presentations and supports their early use to improve diagnostic accuracy, guide appropriate therapy, and avoid unnecessary invasive procedures.