Paget ‘s Disease: Not So Typical for Atypical Femur Fracture

Introduction: Atypical femur fractures (AFF) are reported in patients taking prolonged bisphosphonate therapy, but Paget’s disease (PD) has been rarely reported as a cause of AFF. Case: 71-year-old female with past medical history of right hip osteoarthritis, seizure disorder, hypertension, and Hashimoto’s thyroiditis presented with persistent right hip pain. There was no history of trauma or fall. She had otosclerosis with bilateral hearing loss and bilateral stapedectomies. Her medications were primidone, levothyroxine, lisinopril-hydrochlorothiazide, and vitamin D. She did not smoke tobacco or drink alcohol. She had elevated serum alkaline phosphatase of 300 U/L (35–104). The X-ray of the skull was negative for any cortical thickening. CT of right femur revealed cortical thickening and coarsening of trabeculae of the proximal right femur consistent with PD and incomplete atypical subtrochanteric proximal fracture. Urine NTx 303 BCE/mM Cr (<89). Bone scan showed uptake in the R proximal femur, L distal tibia, and L3-L4 vertebral bodies suspicious of PD. DXA showed osteopenia. She was given zoledronic acid 5 mg IV. Discussion: PD leads to an increased incidence of fractures particularly of the lower extremities with most fractures transverse in nature. Non-union is not uncommon(1). Stress fractures in PD are caused by disorganized bone remodeling due to excessive breakdown and formation of bone. Our patient met the major criteria for AFF as per the ASBMR 2010 task force report but there was no exposure to bisphosphonates(2). The ASBMR task force recommended that bisphosphonates should be discontinued in patients with bisphosphonate-associated AFF due to their severely suppressed bone turnover status. On the other hand, the AFF in patients with PD may heal in response to bisphosphonate treatment. References: 1. Singer FR. Bone Quality in Paget’s Disease of Bone. Curr Osteoporos Rep. 2016;14(2):39–42. DOI:10.1007/s11914-016-0303-62. Shane E, Burr D, Ebeling PR, Abrahamsen B, Adler RA et.al. Atypical subtrochanteric and diaphyseal femoral fractures: report of a task force of the American Society for Bone and Mineral Research. J Bone Miner Res. 2010; 25:2267–2294.