skip to main content

Q Fever Endocarditis — SCE Infectious Diseases MCQ

Instant feedback + full explanation. One question, done properly.

HardBone & Joint InfectionQ Fever EndocarditisSCE Infectious Diseases

A 50-year-old man with a mechanical heart valve presents with low-grade fever for 6 weeks and culture-negative endocarditis despite optimal blood culture technique. He keeps pigeons at home. Coxiella burnetii phase I IgG is 1:2048 and phase II IgG is 1:512. What is the most appropriate treatment and duration?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Doxycycline 100 mg BD plus Hydroxychloroquine 200 mg TDS for at least 18 months

Phase I IgG ≥1:800 with a compatible clinical syndrome (endocarditis) is diagnostic of chronic Q fever. This is a major Duke criterion. Chronic Q fever endocarditis requires prolonged treatment: Doxycycline 100 mg BD plus Hydroxychloroquine 200 mg TDS for a minimum of 18 months (some authorities recommend 24 months or monitoring phase I IgG for decline to <1:200). Hydroxychloroquine alkalinises the phagolysosome, enhancing intracellular killing of C. burnetii. Regular ophthalmological monitoring is needed for Hydroxychloroquine retinal toxicity.

Reference: ESC 2023 – Endocarditis guidelines; UKHSA 2022 – Q fever guidance