LRP5 and osteoporosis: Gain‐of‐function mutations in LRP5 and LRP6 can also cause extreme HBM.7, 8 Together these sclerosing bone dysplasias are characterized by mandible enlargement with tori of the palate and mandible, bone overgrowth leading to nerve compression, a tendency to sink when swimming, and, importantly, resistance to fracture.5, 7, 9 These important gene discoveries validate the study of rare monogenic HBM as an approach to identify novel therapeutic targets for drug development toward osteoporosis treatments.