Bilateral atypical femoral fractures in a patient prescribed denosumab - a case report.

Atypical fractures of the diaphyseal femoral shaft have been reported in the literature at an increasing rate over the past few years. They have been observed mostly in patients who have been on prolonged courses of bisphosphonates, with no reported cases of atypical femoral fractures in those treated with other anti-resorptive medications. A 59 year old woman sustained an atypical fracture of her right femur in March 2013. She had a past medical history of rheumatoid arthritis and osteoporosis. She had been on alendronate but it was discontinued after five years in 1999. She received denosumab by subcutaneous injection in December 2012. At follow up, she complained of pain in her left femur and a radiograph revealed atypical appearances. She was admitted in June 2013 for prophylactic nailing of the left femur. To our knowledge, this is the first reported case of bilateral atypical femoral changes in a patient prescribed denosumab. Given that denosumab has been on the market for a short time period, we expect that the number of these cases will increase with time. We emphasise previous guidance that patients who present with new onset hip or thigh pain should be screened for atypical femoral fractures.