They have been classified into two autosomal recessive forms caused by mutations in the SOST gene coding for sclerostin—Van Buchem’s disease (OMIM #239100) and sclerosteosis (OMIM #269500)—and an autosomal dominant high bone mass (HBM) phenotype [2], now known to comprise two disorders called LRP5 HBM (OMIM # 144750) and LRP6 HBM [3]. This evidence concerns the gene SOST and sclerosteosis.