Juvenile Paget's Disease From Heterozygous Mutation of SP7 Encoding Osterix (Specificity Protein 7, Transcription Factor SP7)

• Published in: Bone (New York, N.Y.) Vol. 137; p. 115364
• Main Authors: Whyte, Michael P., Campeau, Philippe M., McAlister, William H., Roodman, G. David, Kurihara, Nori, Nenninger, Angela, Duan, Shenghui, Gottesman, Gary S., Bijanki, Vinieth N., Sedighi, Homer, Veis, Deborah J., Mumm, Steven
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.08.2020
• Subjects: Alkaline phosphatase; Bone remodeling; Child, Preschool; Dental pathology; Dento-osseous disease; Female; Fractures; Homozygote; Humans; Hyperostosis; Hyperphosphatasemia; Measles virus; Mutation - genetics; Osteitis Deformans - genetics; Osteoblast; Osteoclast; Osteoprotegerin; Osteoprotegerin - genetics; Osteosclerosis; Osterix; Paget bone disease; RANK Ligand; Sequence Deletion; Sp7 Transcription Factor; Transcription Factors; Woven bone; Young Adult; Dental pathology; Alkaline phosphatase; Dento-osseous disease; Paget bone disease; Osteoclast; Bone remodeling; Hyperostosis; Osteoprotegerin; Hyperphosphatasemia; Fractures; Osterix; Osteoblast; Osteosclerosis; Woven bone; Measles virus
• ISSN: 8756-3282; 1873-2763
• DOI: 10.1016/j.bone.2020.115364

Juvenile Paget's disease (JPD) became in 1974 the commonly used name for ultra-rare heritable occurrences of rapid bone remodeling throughout of the skeleton that present in infancy or early childhood as fractures and deformity hallmarked biochemically by marked elevation of serum alkaline phosphatase (ALP) activity (hyperphosphatasemia). Untreated, JPD can kill during childhood or young adult life. In 2002, we reported that homozygous deletion of the gene called tumor necrosis factor receptor superfamily, member 11B (TNFRSF11B) encoding osteoprotegerin (OPG) explained JPD in Navajos. Soon after, other bi-allelic loss-of-function TNFRSF11B defects were identified in JPD worldwide. OPG inhibits osteoclastogenesis and osteoclast activity by decoying receptor activator of nuclear factor κ-B (RANK) ligand (RANKL) away from its receptor RANK. Then, in 2014, we reported JPD in a Bolivian girl caused by a heterozygous activating duplication within TNFRSF11A encoding RANK. Herein, we identify mutation of a third gene underlying JPD. An infant girl began atraumatic fracturing of her lower extremity long-bones. Skull deformity and mild hearing loss followed. Our single investigation of the patient, when she was 15 years-of-age, showed generalized osteosclerosis and hyperostosis. DXA revealed a Z-score of +5.1 at her lumbar spine and T-score of +3.3 at her non-dominant wrist. Biochemical studies were consistent with positive mineral balance and several markers of bone turnover were elevated and included striking hyperphosphatasemia. Iliac crest histopathology was consistent with rapid skeletal remodeling. Measles virus transcripts, common in classic Paget's disease of bone, were not detected in circulating mononuclear cells. Then, reportedly, she responded to several months of alendronate therapy with less skeletal pain and correction of hyperphosphatasemia but had been lost to our follow-up. After we detected no defect in TNFRSF11A or B, trio exome sequencing revealed a de novo heterozygous missense mutation (c.926C>G; p.S309W) within SP7 encoding the osteoblast transcription factor osterix (specificity protein 7, transcription factor SP7). Thus, mutation of SP7 represents a third genetic cause of JPD. •Juvenile Paget's disease (JPD) features heritable, remarkably fast, bone turnover.•Onset is typically early childhood with skeletal pain, fracture, and deformity.•Deactivation or activation of TNFRSF11B (OPG) or A (RANK), respectively, causes JPD.•We identify altered SP7 encoding osterix as the third genetic basis for JPD.