Fibrin ring granulomas in Rickettsia typhi infection.

We describe a 71-year-old man hospitalized for fever and productive cough. Laboratory investigation showed anemia, thrombocytopenia, elevated transaminases, hyponatremia, and hypoalbuminemia. Computerized tomography of the abdomen, thorax, and sinuses, echocardiography, and a gallium scan did not reveal the source of the fever. The patient remained febrile despite courses of piperacillin-tazobactam/azithromycin and ceftriaxone/vancomycin. A bone marrow biopsy showed fibrin ring granulomas, and 2 rickettsial serologic panels were positive for Rickettsia typhi infection and negative for Q fever. The patient was given doxycycline, and the fever resolved within 48 h. We propose that fibrin ring granulomas also occur in murine typhus.