LRP5 and osteoporosis: Atypical femoral fractures (AFFs) have been reported in individuals with the following monogenic bone disorders and their associated genes: osteogenesis imperfecta (COL1A1/COL1A2), pycnodysostosis (CTSK), hypophosphatasia (ALPL), X-linked osteoporosis (PLS3), osteopetrosis, X-linked hypophosphatemia (PHEX), and osteoporosis-pseudoglioma syndrome (lipoprotein receptor-related protein 5 (LRP5)) [1].