# Bartonellosis in a Renal Transplant Recipient: Scratching More Than the Surface

## TL;DR

A renal transplant recipient with fever of unknown origin was diagnosed with bartonellosis after a delayed recognition of a cat scratch and advanced diagnostic testing.

## Contribution

This case emphasizes the importance of considering zoonotic infections in immunosuppressed patients and the diagnostic value of PCR and PET-CT.

## Key findings

- Bartonella henselae was diagnosed in a renal transplant recipient via PCR and PET-CT after initial misdiagnosis.
- Treatment with azithromycin resolved fever and inflammatory markers, with imaging showing splenic normalization.
- The case underscores the need for a high suspicion of zoonotic infections in transplant patients with unexplained symptoms.

## Abstract

Fever of unknown origin (FUO) presents a significant diagnostic challenge in renal transplant recipients due to their immunosuppressed state, which predisposes them to a broad spectrum of potential non-infectious and infectious causes, including atypical pathogens. Among these, Bartonella henselae, the agent of bartonellosis or cat scratch disease (CSD), is a rare but significant pathogen in this population, capable of causing several systemic manifestations, including hepatosplenic involvement. We describe the case of a 60-year-old male renal transplant recipient who presented with FUO, diarrhea, and hepatosplenomegaly six months post transplantation. The absence of classical features of CSD such as regional lymphadenopathy, along with the initial omission of relevant exposure history, delayed diagnosis. A comprehensive diagnostic workup, guided by a thorough review of history that revealed a cat scratch three weeks prior to presentation, positive polymerase chain reaction (PCR) testing for B. henselae, and positron emission tomography-computed tomography (PET-CT) findings of increased splenic uptake with a nodular lesion, corroborated the diagnosis of bartonellosis with splenic involvement. Treatment with azithromycin led to complete resolution of fever and inflammatory markers, and follow-up imaging demonstrated normalization of splenic abnormalities. This case highlights the importance of maintaining a high index of suspicion for zoonotic infections in renal transplant recipients, leveraging advanced diagnostic tools, and tailoring antimicrobial therapy to accommodate immunosuppressive regimens.