LRP5 and osteoporosis-pseudoglioma syndrome: Although homozygous loss-of-function and gain-of-function mutations in the LRP5 gene (OMIM #603506) have been previously described as causative of osteoporosis pseudoglioma syndrome (OPGG) (MIM 259770) and high BMD syndrome (MIM 601884) [12,13], respectively, recent evidence has suggested that polymorphisms of this gene could also the cause of reduced bone mass and size [14,15,16].