A 54-year-old cattle farmer has four months of low-grade fever, night sweats, and progressive exertional dyspnoea. Multiple blood cultures are negative. Transoesophageal echo shows a mitral valve vegetation. Phase I IgG antibodies against Coxiella exceed 1:800. Which feature is most characteristic of this form of infective endocarditis?
- A It typically involves previously normal valves with rapid destruction
- B It accounts for the majority of blood culture-negative endocarditis cases in regions where it is endemic ✓
- C Vegetations are small and embolisation is rare
- D It responds reliably to a two-week course of ceftriaxone
Correct answer: B. It accounts for the majority of blood culture-negative endocarditis cases in regions where it is endemic
Explanation
Chronic Q fever endocarditis caused by Coxiella burnetii is one of the commonest causes of blood culture-negative endocarditis worldwide and often arises on previously damaged or prosthetic valves. Vegetations are large, embolisation is frequent, and treatment requires prolonged combination therapy with doxycycline plus hydroxychloroquine for at least 18 months. The diagnosis rests on serology with phase I IgG titre above 1:800, since blood cultures are invariably sterile.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.