Management of Coxiella burnetii Endocarditis in a Child With Congenital Heart Disease.

A 6-year-old male patient with pulmonary atresia and recent valve replacement with a Melody valve presented with a 6-week history of fever and cough. He was diagnosed with Coxiella burnetii endocarditis based on a C. burnetii Phase I IgG antibody titre of 1:65,536 and increased metabolic activity surrounding his prosthetic cardiac valve on positron emission tomography scan. Treatment was initiated with doxycycline and hydroxychloroquine. However, despite dose escalation, target plasma concentrations were not achieved. The patient experienced rapid clinical improvement, and serological markers declined gradually. Antimicrobial therapy was discontinued after 40 months, as predefined serological criteria were met, clinical course was favourable, and a follow-up positron emission tomography scan demonstrated a significant reduction in metabolic activity around the prosthetic valve. Up to 23 months after cessation of therapy, the patient showed no evidence of active C. burnetii endocarditis during follow-up. The Melody valve maintained its function, and valve replacement was not required. Clinicians should employ an individualised treatment approach to children with C. burnetii endocarditis.