[Q fever: bone marrow characteristic granuloma].

Q fever is a worldwise zoonosis, caused by an obligate intracellular bacterium, Coxiella burnetii. In humans, acute disease, when symptomatic, can manifest by a flu-like illness, pneumonia or hepatitis. Patients with predisposing conditions can evolve with chronic disease, which major clinical presentation is endocarditis with negative routine blood cultures. Histological studies of Q fever based on infected organs biopsies (liver and bone marrow) have demonstrated a distinctive type of granuloma, typically appearing as a "doughnut" granuloma, characterized by a central clean space surrounded by inflammatory cells and rimmed with an eosinophilic fibrinoid material. We describe a 37-year-old man, admitted to hospital for persistent fever. Bone marrow biopsy showed the characteristic "doughnut" granuloma, suggesting a Q fever. Diagnosis was then confirmed by serological tests for C. burnetii.