Pleural effusion caused by Rickettsia felis infection.

INTRODUCTION: Rickettsia felis, a Gram-negative obligate intracellular prokaryotic organism, causes human infections with atypical clinical presentations, commonly including fever, fatigue, headache, and maculopapular rash. CASE PRESENTATION: This study presents a rare case of pleural effusion (PE) associated with R. felis infection, confirmed through targeted next-generation sequencing (tNGS). The patient showed significant clinical improvement and resolution of PE following empirical moxifloxacin followed by pathogen-directed therapy with rifampicin and azithromycin, along with supportive measures for circulation and immune function. CONCLUSIONS: This case report aims to enhance early diagnosis and therapeutic strategies for R. felis infections by sharing the diagnostic and management experience.