In 2001, inactivating mutations in LRP5 were identified as the causative genetic basis for OPPG.(37) Analysis showed that Lrp5 was expressed by cells in the osteoblast lineage, but not by osteoclasts, and much of the subsequent work has focused on this cell type as the central mediator of its actions on bone. Here, LRP5 is linked to osteoporosis-pseudoglioma syndrome.