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Objectives: To estimate the prevalence of chondrocalcinosis and calcium pyrophosphate dihydrate deposition disease (CPPD) in patients with low alkaline phosphatase (ALP) levels and a positive ALPL genetic study (+GT) for hypophosphatasia (HPP) compared to those with the same biochemical abnormality and a negative genetic test (-GT). As a secondary objective, to analyze the biochemical factors associated with its presence in subjects with ALPL variants., Methods: Seventy-eight subjects with persistently low ALP levels and ALPL genetic test were included. Baseline and 24-mo knee ultrasounds were performed in 42 + GT and 36 -GT subjects, in whom the fibrocartilage, hyaline cartilage of menisci, tendons, and synovial fluid were scanned to detect calcium pyrophosphate deposits. A MyLabTwice ultrasound machine (Esaote) with a multifrequency linear array transducer (4-13 MHz) was used., Results: A higher percentage of chondrocalcinosis was observed in the +GT group [9/42 (21.4%)] compared to the -GT group [2/36 (5.6%), p =.045)]. Two patients (4.76%), both in the +GT group, had arthritis secondary to CPPD. No new cases were identified at the 24-mo control. When comparing +GT patients with and without chondrocalcinosis, ALP levels were lower, and pyridoxal-5'-phosphate (PLP) and phosphate levels were higher in the former group ( p <.05). Logistic regression analysis revealed that higher PLP levels are associated with the presence of chondrocalcinosis (OR: 1.1; 95% confidence interval, CI, 1.001-1.012)., Conclusions: Chondrocalcinosis was a frequent ultrasonographic finding in HPP. Arthritis secondary to calcium pyrophosphate deposits, however, proved less prevalent. Genetic causes, such as HPP, should be considered when evaluating patients with chondrocalcinosis in clinical practice., Competing Interests: P.A. and C.T. have received fees for advisory board participation from Alexion Pharmaceuticals and have been recipients of a research grant from this biopharmaceutical company, but not for this original manuscript. The rest of authors declare that they do not have any other conflict of interest regarding the publication of this article., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society for Bone and Mineral Research.)

The SUNFLOWER study was initiated in Japan and South Korea to clarify the course of X-linked hypophosphatemic rickets/osteomalacia (XLH); delineate its physical, mental, and financial burdens; and collect information on treatment. Here, we report cross-sectional data at the time of patient enrollment to better understand the real-world management and complications in patients with XLH and examine the effect of XLH on quality of life (QOL). This is an ongoing, longitudinal, observational cohort study of patients with a diagnosis of XLH. Data from 147 patients (118 in Japan and 29 in South Korea) were evaluated. In total, 77 children (mean age, 9.7 yr; 67.5% female) and 70 adults (mean age, 37.6 yr; 65.7% female) were enrolled. PHEX gene mutations were confirmed in 46/77 (59.7%) children and 37/70 (52.9%) adults. Most patients in both age groups were receiving a combination of phosphate and active vitamin D at baseline. The mean height Z-score was -2.21 among adults (male: -2.34; female: -2.14). The mean Rickets Severity Score in children was 1.62. Whereas children appeared to have low pain levels (mean revised faces pain scale score, 1.3), adults reported mild-to-moderate pain (mean Brief Pain Inventory pain severity, 2.02). Mean QOL in children (assessed using the 10-item short-form health survey for children) was low, with a score below normative level for physical functioning. In adults, results from the Western Ontario and McMaster Universities osteoarthritis index indicated the presence of pain, stiffness, and decreased physical function. The respective mean total days/year of work/school non-attendance due to symptoms/complications and management of XLH were 0.7 and 3.0 among adults, and 6.4 and 6.1 among children. Our findings reconfirmed a relationship between disease and QOL in patients with XLH. We anticipate that these data will be important in enabling clinicians to understand the daily reality of patients with XLH., Competing Interests: N.N. received support for the present manuscript (eg, funding and medical writing support funding) from Kyowa Kirin Co., Ltd. to the author’s institution; consulting fees and payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing, or educational events from Kyowa Kirin; and served a leadership or fiduciary role as Director for the Japanese Society for Pediatric Endocrinology (JSPE), Chair for the Bone and Mineral Metabolism Committee of the JSPE, and Chair for the Scientific Program Committee of the Asia Pacific Paediatric Endocrine Society (APPES). N.I. received support for the present manuscript (eg, funding and medical writing support funding) from Kyowa Kirin Co., Ltd. to the author’s institution, and grants and consulting fees from Kyowa Kirin Co., Ltd. Division of Therapeutic Development for Intractable Bone Diseases, Graduate School of Medicine and Faculty of Medicine, The University of Tokyo is an endowment department, supported with Kyowa Kirin Co., Ltd. T.M. received support for the present manuscript (eg, funding and medical writing support funding) from Kyowa Kirin Co., Ltd. to the author’s institution; consulting fees from Kyowa Kirin Co., Ltd., and Alexion Pharmaceuticals Inc.; and payment or honoraria for lectures, presentations, speakers’ bureaus, manuscript writing, or educational events from Kyowa Kirin Co., Ltd., Alexion Pharmaceuticals Inc., Amgen Inc., Chugai Pharmaceuticals Co., Ltd., and Novo Nordisk. H.G.K. received grants or contracts from ChongKunDang, Handok, Kyowa Kirin, Amgen, Apellis Pharmaceuticals, and AstraZeneca; consulting fees from Handok and Kyowa Kirin; payment or honoraria for lectures, presentations, speakers’ bureaus, manuscript writing or educational events from Alexion, Handok, and Kyowa Kirin; and participated on a Data Safety Monitoring Board or Advisory Board for Bayer. T.K. received support for the present manuscript (eg, funding and medical writing support funding) from Kyowa Kirin Co., Ltd. to the author’s institution; and consulting fees from Kyowa Kirin Co., Ltd. A.S. received support for the present manuscript (eg, funding and medical writing support funding) from Kyowa Kirin Co., Ltd. to the author’s institution; consulting fees from Chugai Pharmaceutical (to the author’s institution), Daiichi Sankyo (to the author’s institution), Kyowa Kirin (to the author’s institution), Takeda Pharmaceutical Company Limited (to the author and author’s institution), and Shionogi Pharma (to the author); and payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events from AbbVie, Asahi Kasei Corporation, AstraZeneca PLC, Astellas Pharma, Bayer Yakuhin, Bristol Myers Squibb, Chugai Pharmaceutical, Daiichi Sankyo, Eisai, Janssen Pharmaceutical, Kissei Pharmaceutical, Kyowa Kirin, Mallinckrodt Pharmaceuticals, Merck Biopharma, Maruho, Mitsubishi Tanabe Pharma Corporation, Nipro Corporation, Novo Nordisk Pharma, Nippon Shinyaku, Ono Pharmaceutical, Pfizer, Takeda Pharmaceutical Company Limited, Taisho Pharmaceutical, and Torii Pharmaceutical. D.K. received support for the present manuscript (eg, funding and medical writing support funding) from Kyowa Kirin Co., Ltd. to the author’s institution and consulting fees from Kyowa Kirin Co., Ltd. Y.N. is an employee of Kyowa Kirin Co., Ltd. S.F. received support for the present manuscript (eg, funding and medical writing support funding) from Kyowa Kirin Co., Ltd. and consulting fees from Kyowa Kirin Co., Ltd. K.O. has received consulting fees and payment or honoraria from Kyowa Kirin Co., Ltd., and served a leadership or fiduciary role in the JSPE. O.M. declares no competing interests., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society for Bone and Mineral Research.)

Hypophosphatasia (HPP), caused by loss-of-function mutations in the ALPL gene encoding tissue-nonspecific alkaline phosphatase (TNAP), is characterized by skeletal and dental hypomineralization that can vary in severity from life-threatening to milder manifestations only in adulthood. PHOSPHO1 deficiency leads to early-onset scoliosis, osteomalacia, and fractures that mimic pseudo-HPP. Asfotase alfa, a life-saving enzyme replacement therapy approved for pediatric-onset HPP, requires subcutaneous injections 3 to 6 times per week. We recently showed that a single injection of an adeno-associated virus vector serotype 8 harboring TNAP-D 10 (AAV8-TNAP-D 10 ) effectively prevented skeletal disease and prolonged life in Alpl -/- mice phenocopying infantile HPP. Here, we aimed to determine the efficacy of AAV8-TNAP-D 10 in improving the skeletal and dental phenotype in the Alpl Prx1/Prx1 and Phospho1 -/- mouse models of late-onset (adult) HPP and pseudo-HPP, respectively. A single dose of 3 × 10 11 vector genomes per body (vg/b) was injected intramuscularly into 8-week-old Alpl Prx1/Prx1 and wild-type (WT) littermates, or into 3-day-old Phospho1 -/- and WT mice, and treatment efficacy was evaluated after 60 days for late-onset HPP mice and after 90 days for Phospho1 -/- mice. Biochemical analysis showed sustained serum alkaline phosphatase activity and reduced plasma PP i levels, and radiographic images, micro-computed tomography (micro-CT) analysis, and hematoxylin and eosin (H&E) staining showed improvements in the long bones in the late-onset HPP mice and corrected scoliosis in the Phospho1 -/- mice. Micro-CT analysis of the dentoalveolar complex did not reveal significant changes in the phenotype of late-onset HPP and pseudo-HPP models. Moreover, alizarin red staining analysis showed that AAV8-TNAP-D 10 treatment did not promote ectopic calcification of soft organs in adult HPP mice after 60 days of treatment, even after inducing chronic kidney disease. Overall, the AAV8-TNAP-D 10 treatment improved the skeletal phenotype in both the adult HPP and pseudo-HPP mouse models. This preclinical study will contribute to the advancement of gene therapy for the improvement of skeletal disease in patients with heritable forms of osteomalacia. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research., Competing Interests: JLM is a consultant for Aruvant. JLM and KM are co‐inventors of a patent application for the use of viral‐mediated administration of mineral‐targeted TNAP for the treatment of HPP and pseudo‐HPP. FAO, FFM, YK, SN, CF, and BLF state that they have no conflicts of interest., (© 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.)

Tumor-induced osteomalacia (TIO) is a rare cause of impaired bone mineralization mediated by the osteocyte-derived, phosphaturic hormone: fibroblast growth factor 23 (FGF23). The case is presented of a previously healthy 45-year-old man who developed fragility fractures at multiple sites (initially metatarsals, eventually ribs, hips, spine, scapula, and sacrum) resulting in rapid functional deterioration, weakness, and the inability to bear weight and ambulate without a walker. Workup for secondary causes of bone loss was negative except for mild hypogonadotropic hypogonadism with normal pituitary MRI and hypophosphatemia that persisted despite aggressive supplementation. Testosterone was initiated but discontinued 6 months later because of deep vein thrombosis and pulmonary embolism, likely provoked by his new sedentary state, in addition to smoking history and possibly testosterone usage. Serum FGF23 was nonelevated at 138 mRU/mL (44-215). A genetic panel for OI variants was negative for a causal mutation. At the age of 48, 3 years after his initial fracture, he was referred to our academic endocrine clinic. We ruled out additional mutations that lead to hypophosphatemic rickets, including phosphate-regulating endopeptidase homolog, X-linked. PET/CT looking for a potential TIO locus revealed uptake in the left suprapatellar recess. Biopsy was consistent with a phosphaturic mesenchymal tumor. FGF23 was repeated for a preoperative baseline and now found to be elevated at 289 mRU/mL. In retrospect, it is likely that the initial level was inappropriately elevated for the degree of hypophosphatemia. After resection, he experienced marked improvement in physical function, decreased pain, and resolution of renal phosphate wasting. The principals of establishing a robust clinical diagnosis of TIO should be emphasized, excluding other entities and avoiding pitfalls in the interpretation of laboratory testing. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research., (© 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.)

Genetically modified mice have provided novel insights into the mechanisms of activation and inactivation of vitamin D, and in the process have provided phenocopies of acquired human disease such as rickets and osteomalacia and inherited diseases such as pseudovitamin D deficiency rickets, hereditary vitamin D resistant rickets, and idiopathic infantile hypercalcemia. Both global and tissue-specific deletion studies leading to decreases of the active form of vitamin D, calcitriol [1,25(OH) 2 D], and/or of the vitamin D receptor (VDR), have demonstrated the primary role of calcitriol and VDR in bone, cartilage and tooth development and in the regulation of mineral metabolism and of parathyroid hormone (PTH) and FGF23, which modulate calcium and phosphate fluxes. They have also, however, extended the spectrum of actions of calcitriol and the VDR to include, among others: modulation, jointly and independently, of skin metabolism; joint regulation of adipose tissue metabolism; cardiovascular function; and immune function. Genetic studies in older mice have also shed light on the molecular mechanisms underlying the important role of the calcitriol/VDR pathway in diseases of aging such as osteoporosis and cancer. In the course of these studies in diverse tissues, important upstream and downstream, often tissue-selective, pathways have been illuminated, and intracrine, as well as endocrine actions have been described. Human studies to date have focused on acquired or genetic deficiencies of the prohormone vitamin D or the (generally inactive) precursor metabolite 25-hyrodxyvitamin D, but have yet to probe the pleiotropic aspects of deficiency of the active form of vitamin D, calcitriol, in human disease. © 2020 American Society for Bone and Mineral Research © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research., (© 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.)

We describe two women with a misdiagnosed fracturing bone disease who were treated erroneously with i.v. zoledronate. Over the next year, they suffered marked clinical and radiographic deterioration in skeletal disease. Both were eventually diagnosed with hypophosphatemic osteomalacia secondary to acquired Fanconi syndrome (caused by light-chain myeloma in one case and tenofovir treatment in the other). Appropriate treatment with phosphate supplementation was instituted with clinical improvement. These cases illustrate the importance of not missing osteomalacia in adults presenting with fractures, and the potentially damaging effects of treatment with long-acting inhibitors of bone resorption in these circumstances. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research., (© 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.)

X-linked hypophosphatemia (XLH) is a disease caused by abnormally elevated FGF23 levels, which cause persistent hypophosphatemia accompanied by subsequent reduction in bone mineralization that presents as rickets or osteomalacia. Burosumab is a fully human monoclonal antibody targeting FGF23 that is under development for the treatment of FGF23-related hypophosphatemia including XLH. The safety, tolerability, and proof of concept of burosumab have been evaluated in patients with XLH in previous studies conducted in countries outside of Asia. The objective of this study was to evaluate the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and expression of anti-drug antibodies in Japanese and Korean adults with XLH. This was a multicenter, sequential dose-escalation, open-label, single-dose study. This study began with cohort 1 (s.c. dose of burosumab 0.3 mg/kg), after which the dose was escalated sequentially in cohort 2 (s.c. dose of burosumab 0.6 mg/kg) and cohort 3 (s.c. dose of burosumab 1.0 mg/kg). The PK of burosumab were linear within the dose range of 0.3 to 1.0 mg/kg. The PD effects such as serum phosphorus concentration, serum 1,25[OH] 2 D 3 concentration, and ratio of tubular maximum reabsorption rate of phosphate to glomerular filtration rate (TmP/GFR) were elevated after a single s.c. administration. The area under the receiver-operating characteristic curve from 0 to t (AUC 0-t ) values calculated using the change from baseline values of serum phosphorus, serum 1,25(OH) 2 D 3 , and TmP/GFR were correlated with the AUC 0-t of burosumab. Furthermore, no serious adverse events (AEs), deaths, remarkable increase or decrease in the corrected calcium or intact PTH levels, or signs of nephrocalcinosis or its worsening were observed after treatment. Some AEs and drug-related AEs were observed; however, there were no clinically meaningful tendencies. The positive effects and acceptable safety profile seen in this study are encouraging for Japanese and Korean patients with XLH., (© 2018 The Authors published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.)