# P-79. Experience of Bartonella henselae Osteomyelitis in the Pediatric Population at Texas Children’s Hospital: A Retrospective Review from 2004-2025

## TL;DR

This study reviews cases of Bartonella henselae osteomyelitis in children, highlighting its rare but possible spinal and bone presentations and treatment challenges.

## Contribution

The paper provides a retrospective analysis of pediatric Bartonella henselae osteomyelitis cases at a single hospital system over 21 years.

## Key findings

- Osteomyelitis was most commonly found in the vertebral column and pelvis in pediatric patients.
- Bartonella PCR from tissue biopsies had a low diagnostic yield, with 71.4% of tests negative.
- Azithromycin and rifampin were the most commonly used antibiotic regimens for treatment.

## Abstract

Bartonella henselae is a fastidious, aerobic, intracellular, gram-negative bacillus that causes cat scratch disease (CSD). There is a wide spectrum of presentations of CSD, the most common presentation is localized lymphadenopathy, but disseminated forms can occur reflecting likely hematogenous spread. Osteomyelitis is an unusual presentation of CSD.

Figure 1Focal hyperintense signal with abnormal enhancement in the body and pedicle of L2 on the left associated with a small left paraspinal phlegmon centered at L2.

Focal hyperintense signal with abnormal enhancement in the body and pedicle of L2 on the left associated with a small left paraspinal phlegmon centered at L2.

Figure 2Multiple small foci of eccentric marrow signal abnormality and enhancement with adjacent periostitis in the bilateral femurs.

Multiple small foci of eccentric marrow signal abnormality and enhancement with adjacent periostitis in the bilateral femurs.

This is a retrospective case series from patients from 2004 to 2025 across the Texas Children’s Hospital system. The cohort was identified using ICD9/10 codes for “osteomyelitis” and “bartonellosis” or “cat scratch disease” in both the inpatient and outpatient setting. Diagnosis is established with positive serology, a positive Bartonella spp PCR result from tissue, or positive microbial cell-free DNA sequencing (Karius) test for Bartonella henselae. Positive serology was defined as probable CSD with patients having IgM >1:16 or IgG 1:64 – 1:256, or definitive CSD defined as IgG >1:256. Osteomyelitis diagnosis was based on magnetic resonance imaging (MRI), clinical presentation, and elevated inflammatory markers.

Table 1. Demographics, exposure, presenting symptoms, diagnosis, and treatment as documented in the medical record

The ICD 9/10 codes identified 26 patients, of which 18 met criteria for Bartonella henselae osteomyelitis (Table 1). The median age of presentation was 8 years (n=18, range from 2 to 17 years), with 50% identified as white. All patients presented osteoarticular pain and all underwent MRI (Figures 1, 2). The most common sites for osteomyelitis were vertebral (55.6%) and pelvis (22.2%); 22.2% was multifocal. One patient was diagnosed based solely on Karius while all other patients had positive serology. Of the biopsies undergoing PCR (7), 5 (71.4%) were negative. The most commonly used antibiotic regimen was azithromycin and rifampin (50%), or trimethoprim-sulfamethoxazole and rifampin (27.8%) with a median duration of 31 days. One patient did not receive treatment with subsequent resolution of radiological findings.

Osteomyelitis in cat scratch disease should be suspected in patients with osteoarticular pain and positive serology. Bartonella PCR from tissue biopsy has a low diagnostic yield. More studies are needed to determine preferred treatment and duration.

All Authors: No reported disclosures