LRP5 and osteoporosis-pseudoglioma syndrome: It has been reported that loss-of-function mutations of the LRP5 gene cause osteoporosis-pseudoglioma (OPPG), an autosomal recessive disease characterized by low bone mass and childhood fractures [15], whereas the LRP5 G171V mutation is associated with autosomal dominant high bone mass (HBM) traits [16–18].