SP7 and juvenile Paget disease: Juvenile Paget disease (JPD, MIM # 239000) is mainly caused by biallelic inactivating mutations in the TNFRSF11B gene that encodes osteoprotegerin (OPG) [1, 2], although mutations in other genes, including TNFRSF11A encoding receptor activator of nuclear factor-κB (RANK) [3] and specificity protein7 (SP7) encoding osterix [4], have been causally linked with JPD [5].