Subacute, tetracycline-responsive, granulomatous osteomyelitis in an adult man, consistent with Q fever infection.

Osteomyelitis due to Coxiella burnetii infection is a rare condition in adults. We report the case of a healthy young man presenting with subacute osteomyelitis of the left cheek bone, evolving gradually after an episode of acute febrile illness. Histological evaluation confirmed subacute granulomatous inflammation. Despite antibody titres not reaching the standard cut-off for chronic Q fever (phase I IgG 1/160, phase II IgG 1/2560), osteomyelitis was radiologically and histologically confirmed. A 6-month course of doxycycline/hydroxychloroquine brought clinical and radiological cure while various conventional antibiotic treatments had failed to improve the clinical condition. Currently, at 6-month follow-up, no relapse has occurred and antibody titres have declined. A shorter course of doxycycline/hydroxychloroquine than that used for chronic Q fever osteomyelitis may be sufficient to treat subacute Q fever osteomyelitis in some cases.