Bilateral atraumatic neck of femur fractures secondary to tenofovir-induced fanconi syndrome

Background: Tenofovir is an effective drug in the treatment of chronic hepatitis B. However, it has been associated with adverse complication of Fanconi syndrome due to proximal renal tubule dysfunction. This leads to severe hypophosphatemia and osteomalacia which predisposed patients to fragility fractures. Case report: Here, we report the case of a 67-year old man on tenofovir for chronic hepatitis B, presenting with bilateral atraumatic neck of femur (NOF) fractures. Bone mineral density (BMD) scan of the lumbar spine revealed a low T-score of −2.6. Laboratory studies revealed severe hypophosphatemia and hypocalcemia and high alkaline phosphate concentration. A diagnosis of tenofovir-induced Fanconi syndrome was made. Tenofovir was replaced with entecavir and after appropriate optimization with the help of endocrinologist, he underwent a total hip replacement via a direct anterior approach of the more symptomatic left hip. At 1-month post-operation, he was asymptomatic and ambulating well. Conclusion: High index of suspicion and early identification of Fanconi syndrome is required in bilateral atraumatic neck of femur fractures to treat the underlying disorder while planning for surgical intervention. Treatment of NOF fractures in patients with Fanconi syndrome should be a total hip replacement after discontinuing tenofovir and subsequent correction of any electrolyte abnormalities.