Osteomyelitis is usually related to trauma, surgery, immunocompromised patients, IV drug abuse, poor vascular supply, diabetes, sickle cell disease or peripheral neuropathy. We report an unusual case of femur osteomyelitis without any of these risk factors.

A 31 years old male, light smoker, presented at the Emergency Room for pain in the left thigh for about a month, without any previous event. He had 2 previous visits to the hospital with similar diffuse complaints interpreted as irradiated low back pain. He was pale, feverish but no signs of local inflamation. His left knee ROM was 30°-15°-0°. He had no neurologic deficits. Blood tests showed high WBC count and PCR (400mg/L). After contrasted CT showing an 1,2×6×2,5cm abcess the patient was taken to the OR for irrigation and debridment.

The day after the patient did a MRI that showed extended femur osteomyelitis and adjacent myositis (images). He underwent new surgery for a more extensive irrigation and debridment, femur medular canal included, from where a large pus quantity erupted.

The hemocultures and bone biopsys, revealed a Multissensible Strep. Alfa-hemolitic (S. anginosus) and appropriate antibiotherapy was implemented (Amoxicillin/Clavulanate). He slowed improve till 11th day when he showed rise of PCR and a new MRI showed the same inflammatory process. He underwent new surgery but no pus was visible. He gradually improved, started hyperbaric oxygen therapy and was discharged on the 28th day after the first surgery, continuing antibiotherapy at home for a total of 8 weeks.

Transthoracic Ecography was normal, as well Brucella, HIV, and other serologies.

Three weeks later, the patient again presented to the ER with fever and rise of inflammatory markers in blood, consistent with recurrence of the infection. The patient was taken to the OR for surgical debdridment and irrigation, but this time the cultures showed a multissensible Gemella haemolysans, possible contamination during the hyperbaric oxygen therapy sessions.

This is the case of a healthy young adult with an idiopathic femur osteomyelitis, initially misinterpreted for irradiated low back pain, that recurred after the first medical and surgical successful treatment, with an unusual agent.