Cardiovascular Outcomes of KCNJ5 mutated Aldosterone-Producing Adenoma: A Systematic Review

BACKGROUND

While clinical features of KCNJ5-mutated aldosterone-producing adenoma (APA) have been reported, evidence of its clinical outcomes is lacking. We aimed to synthesize available literature about the associations between KCNJ5 mutation with cardiovascular and metabolic outcomes among patients with APA.

METHODS

In this systematic review of observational studies, MEDLINE and EMBASE were searched through August 2022. Two independent authors screened the search results and extracted data from eligible observational studies investigating cardiovascular or metabolic outcomes between KCNJ5-mutated APAs and KCNJ5-non-mutated APAs. Risk of Bias In Non-randomized Studies of Interventions was used to assess the quality of the included studies.

RESULTS

A total of 573 titles/abstracts were screened and after the expert opinion of the literature, 20 were read the full text, of which 12 studies were included. Across three studies comparing the baseline or change in the cardiac function between KCNJ5-mutated APAs and KCNJ5-non-mutated APAs, all studies reported the association between impaired cardiac functions and KCNJ5 mutation status. Among six studies evaluating the cure of hypertension after surgery, all studies showed that KCNJ5 mutation was significantly associated with the cure of hypertension. In quality assessment, seven studies were at serious risk of bias, while the remaining studies were at moderate risk of bias.

CONCLUSIONS

This systematic review provided evidence of the significant association between KCNJ5 mutation and unfavorable cardiovascular outcomes in patients with primary aldosteronism. Further research is needed to improve the quality of evidence on this topic and elucidate the underlying mechanisms of the potential burden of KCNJ5 mutation.

Extended curettage for tumour-induced osteomalacia in the bone

BACKGROUND

extended curettage is generally used to treat infiltrative bone tumours. However, the extent of the curettage performed in previous studies remains unclear. This study aimed to investigate the efficacy of extended curettage for bone tumour-induced osteomalacia.

METHODS

we included 12 patients with tumour-induced osteomalacia who underwent extended curettage at our hospital between 2000 and 2022. Extended curettage was applied in cases where tumour resection could cause functional impairment or necessitate complex reconstruction. We investigated patients' clinical and oncological outcomes.

RESULTS

patients had a mean age of 55 (24-81) years, and the median follow-up duration after surgery was 3.9 (1.0-14.0) years. The causative tumours were located in the pelvis and lumbar spine. Imaging revealed the tumours to be of the sclerotic, intertrabecular, lytic and mixed types. Intraoperative 3D fluoroscopy was used in 10 patients. Extended curettage with high-speed burring and adjuvant therapy with cauterization using an electric scalpel and ethanol resulted in a remission rate of 83%; no recurrence or metastasis was observed in cases of early postoperative biochemical remission. In cases where the causative tumour was at the lumbar spine and ischium close to the acetabulum, no postoperative biochemical remission was observed, and conservative treatment was continued. Except for one patient with a tumour in the lumbar spine, all patients could walk without a cane.

CONCLUSIONS

extended curettage for bone tumour-induced osteomalacia is oncologically and functionally favourable, especially in cases where resection of the causative tumour could cause functional impairment or necessitate complex reconstruction.

A novel pathogenic variant in fibroblast growth factor 23 outside the furin-recognizing RXXR motif in an autosomal dominant hypophosphatemic rickets patient

INTRODUCTION

Autosomal dominant hypophosphatemic rickets (ADHR) is caused by pathogenic variants in the fibroblast growth factor 23 (FGF23) gene, which plays a key role in the regulation of phosphorus metabolism. FGF23 has the RXXR motif recognized by furin, leading to cleavage between R179 and S180 and thereby inactivating the protein's function. Previously reported variants in FGF23 causing ADHR occurred only affecting residues R176 or R179, which are located in the RXXR motif, leading to impaired cleavage. Impairment of protein cleavage increases bioactive FGF23 levels, subsequently resulting in the development of ADHR.

CASE PRESENTATION

A 13-year-old boy with ADHR with the appearance of rickets on bone radiographs as well as documented hypophosphatemia was found to have a novel S180I variant in the FGF23 gene. Unlike previously reported pathogenic variants, this novel variant was located outside the RXXR motif. Subsequently, western blotting showed that the S180I mutant was resistant to proteolysis than the wild-type, similar to pathogenic variants model mutant (R176Q/R179Q).

CONCLUSION

The novel variant in FGF23 presented herein, found in a patient with ADHR, is the first pathogenic variant found outside the typical furin recognition sequence. It exhibits proteolysis resistance due to impaired cleavage.

Acquired Forms of Fibroblast Growth Factor 23-Related Hypophosphatemic Osteomalacia

Fibroblast growth factor 23 (FGF23) is a pivotal humoral factor for the regulation of serum phosphate levels and was first identified in patients with autosomal dominant hypophosphatemic rickets and tumor-induced osteomalacia (TIO), the most common form of acquired FGF23-related hypophosphatemic rickets/osteomalacia (FGF23rHR). After the identification of FGF23, many other inherited and acquired forms of FGF23rHR were reported. In this review article, the detailed features of each acquired FGF23rHR are discussed, including TIO, ectopic FGF23 syndrome with malignancy, fibrous dysplasia/McCune-Albright syndrome, Schimmelpenning- Feuerstein-Mims syndrome/cutaneous skeletal hypophosphatemia syndrome, intravenous iron preparation-induced FGF23rHR, alcohol consumption-induced FGF23rHR, and post-kidney transplantation hypophosphatemia. Then, an approach for the differential diagnosis and therapeutic options for each disorder are concisely introduced. Currently, the majority of endocrinologists might only consider TIO when encountering patients with acquired FGF23rHR; an adequate differential diagnosis can reduce medical costs and invasive procedures such as positron emission tomography/computed tomography and venous sampling to identify FGF23-producing tumors. Furthermore, some acquired FGF23rHRs, such as intravenous iron preparation/alcohol consumption-induced FGF23rHR, require only cessation of drugs or alcohol to achieve full recovery from osteomalacia.

The pathophysiology of hypophosphatemia

After identification of fibroblast growth factor (FGF) 23 as the pivotal regulator of chronic serum inorganic phosphate (Pi) levels, the etiology of disorders causing hypophosphatemic rickets/osteomalacia has been clarified, and measurement of intact FGF23 serves as a potent tool for differential diagnosis of chronic hypophosphatemia. Additionally, measurement of bone-specific alkaline phosphatase (BAP) is recommended to differentiate acute and subacute hypophosphatemia from chronic hypophosphatemia. This article divides the etiology of chronic hypophosphatemia into 4 groups: A. FGF23 related, B. primary tubular dysfunction, C. disturbance of vitamin D metabolism, and D. parathyroid hormone 1 receptor (PTH1R) mediated. Each group is further divided into its inherited form and acquired form. Topics for each group are described, including "ectopic FGF23 syndrome," "alcohol consumption-induced FGF23-related hypophosphatemia," "anti-mitochondrial antibody associated hypophosphatemia," and "vitamin D-dependent rickets type 3." Finally, a flowchart for differential diagnosis of chronic hypophosphatemia is introduced.

The 2023 Guidelines for the management and treatment of glucocorticoid-induced osteoporosis

INTRODUCTION

Although synthetic glucocorticoids (GCs) are commonly used to treat autoimmune and other diseases, GC induced osteoporosis (GIOP) which accounts for 25% of the adverse reactions, causes fractures in 30-50% of patients, and markedly decreases their quality of life. In 2014, the Japanese Society for Bone and Mineral Research (JSBMR) published the revised guidelines for the management and treatment of steroid-induced osteoporosis, providing the treatment criteria based on scores of risk factors, including previous fractures, age, GC doses, and bone mineral density, for patients aged ≥18 years who are receiving GC therapy or scheduled to receive GC therapy for ≥3 months.

MATERIALS AND METHODS

The Committee on the revision of the guidelines for the management and treatment of GIOP of the JSBMR prepared 17 clinical questions (CQs) according to the GRADE approach and revised the guidelines for the management and treatment of GIOP through systematic reviews and consensus conferences using the Delphi method.

RESULTS

Bisphosphonates (oral and injectable formulations), anti-RANKL antibody teriparatide, eldecalcitol, or selective estrogen receptor modulators are recommended for patients who has received or scheduled for GC therapy with risk factor scores of ≥3. It is recommended that osteoporosis medication is started concomitantly with the GC therapy for the prevention of fragility fractures in elderly patients.

CONCLUSION

The 2023 guidelines for the management and treatment of GIOP was developed through systematic reviews and consensus conferences using the Delphi method.

A PAI-1 antagonist ameliorates hypophosphatemia in the Hyp vitamin D-resistant rickets model mouse

Congenital fibroblast growth factor 23 (FGF23)-related hypophosphatemic rickets/osteomalacia is a rare bone metabolism disorder characterized by hypophosphatemia and caused by genetic abnormalities that result in excessive secretion of FGF23. Hyp mice are a model of X-linked hypophosphatemia (XLH) caused by deletion of the PHEX gene and excessive production of FGF23. The purpose of this study was to investigate the potential of TM5614 as a therapeutic agent for the treatment of congenital FGF23-related hypophosphatemic rickets and osteomalacia in humans by administering TM5614 to Hyp mice and examining its curative effect on hypophosphatemia. After a single oral administration of TM5614 10 mg·kg-1 to female Hyp mice starting at 17 weeks of age, the serum phosphate concentration increased with a peak at 6 h after administration. ELISA confirmed that TM5614 administration decreased the intact FGF23 concentration in the blood. Expression of 25-hydroxyvitamin D-1α-hydroxylase protein encoded by Cyp27b1 mRNA in the kidney was suppressed in Hyp mice, and treatment with 10 mg·kg-1 of TM5614 normalized the expression of 25-hydroxyvitamin D-1α-hydroxylase protein and Cyp27b1 mRNA in the kidneys of these mice. Our data indicate that oral administration of TM5614 ameliorates hypophosphatemia in Hyp mice, suggesting that TM5614 may be an effective treatment for congenital FGF23-related hypophosphatemic rickets and osteomalacia.

Cartilage tissues regulate systemic aging via ectonucleotide pyrophosphatase/phosphodiesterase 1 in mice

Aging presents fundamental health concerns worldwide; however, mechanisms underlying how aging is regulated are not fully understood. Here, we show that cartilage regulates aging by controlling phosphate metabolism via ectonucleotide pyrophosphatase/phosphodiesterase 1 (Enpp1). We newly established an Enpp1 reporter mouse, in which an EGFP-luciferase sequence was knocked-in at the Enpp1 gene start codon (Enpp1/EGFP-luciferase), enabling detection of Enpp1 expression in cartilage tissues of resultant mice. We then established a cartilage-specific Enpp1 conditional knockout mouse (Enpp1 cKO) by generating Enpp1 flox mice and crossing them with cartilage-specific type 2 collagen Cre mice. Relative to WT controls, Enpp1 cKO mice exhibited phenotypes resembling human aging, such as short life span, ectopic calcifications, and osteoporosis, as well as significantly lower serum pyrophosphate levels. We also observed significant weight loss and worsening of osteoporosis in Enpp1 cKO mice under phosphate overload conditions, similar to global Enpp1-deficient mice. Aging phenotypes seen in Enpp1 cKO mice under phosphate overload conditions were rescued by a low vitamin D diet, even under high phosphate conditions. These findings suggest overall that cartilage tissue plays an important role in regulating systemic aging via Enpp1.

The Effect of Asfotase Alfa on Plasma and Urine Pyrophosphate Levels and Pseudofractures in a Patient With Adult-Onset Hypophosphatasia

Hypophosphatasia (HPP) is an inherited disease caused by variants of the ALPL gene encoding tissue-nonspecific alkaline phosphatase. Adult-onset HPP (adult HPP), known as a mild form of HPP, develops symptoms involving osteomalacia after the age of 18 years. Asfotase alfa (AA) is a modulated recombinant human alkaline phosphatase (ALP) that has been established as a first-line therapy for severe forms of HPP, such as perinatal and infantile forms. We described a 64-year-old female who presented with pseudofractures in bilateral femur diaphyses and impaired mobility. Low serum ALP activity and a high concentration of urine phosphoethanolamine indicated the diagnosis of HPP, which was confirmed by the identification of a homozygous variant in the ALPL gene (c.319G > A; p.Val107Ile). An in vitro transfection experiment to measure the ALP activity of this novel variant protein was performed, resulting in 40% of the residual enzymatic activity compared with the wild type. AA was initiated to facilitate the union of pseudofracture and to improve mobility. After 6 months, radiographic images revealed the disappearance of fracture lines, and improvement of ambulatory ability was confirmed by the 6-minute walk test (525 to 606 m). The EQ-5D-5L index was also improved (0.757 to 0.895). Within a follow-up period, the levels of urine pyrophosphate corrected by urine creatinine (uPPi/Cre) declined in parallel with the level of plasma PPi (plasma PPi: 6.34 to 1.04 μM, uPPi/Cre: 226.8 to 75.4 nmol/mg). The beneficial effect of AA on pseudofracture healing in adult HPP was presented, although the application of AA should be restricted to patients exhibiting relatively severe manifestations. In addition, a novel pathogenic variant of the ALPL gene was identified with the supportive result of functional analysis. Furthermore, when monitoring patients with HPP treated with AA, uPPi/Cre might be a convenient substitute for plasma PPi, which requires immediate filtration after blood sampling. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Enlarged right atrium predicts pacemaker implantation after atrial fibrillation ablation in patients with tachycardia-bradycardia syndrome

Introduction

Although catheter ablation (CA) of tachycardia-bradycardia syndrome (TBS) in patients with atrial fibrillation (AF) is considered to be an effective treatment strategy, pacemaker implantations (PMIs) are often required even after a successful CA. This study aimed to elucidate the clinical predictors of a PMI after CA.

Methods

From 2011 to 2020, 103 consecutive patients diagnosed with TBS were retrospectively enrolled in the study. Among the 103 patients, 54 underwent a PMI and 49 CA of AF. During 47.4 ± 35.4 months after 1.4 ± 0.6 CA sessions, 37 (75.5%) of 49 patients were free from atrial arrhythmia recurrences. PMIs were performed in 11 patients (PMI group) and the remaining 38 did not receive a PMI (non-PMI group).

Results

When comparing the PMI and non-PMI groups, there were no differences in the basic mean heart rate (P = 0.36), maximum pauses detected by 24-hour Holter-monitoring (P = 0.61), and other clinical parameters between the two groups while the right atrial area index was larger (42.1 ± 24.0 vs. 21.8 ± 8.4 cm2/m2 P = 0.002) in the PMI group than non-PMI group. The ROC curve analysis showed that the optimal cutoff point of the ratio of the right atrial area index to the left atrial area index for predicting a PMI following CA was 0.812 (Sensitivity 72.7%, specificity 71.1%, positive predictive value 42.1%, negative predictive value 90.0%, diagnostic accuracy 71.4%, AUC = 0.81).

Conclusion

Right atrial enlargement prior to CA was considered to be one of the risk factors for a PMI after CA of AF.

FGF23-related hypophosphatemia in a patient with small cell lung cancer: a case report and literature review

Although there are a few case reports of patients with small cell lung cancer developing hypophosphatemia, detailed information on this condition is scarce. A 52-year-old patient with advanced stage small cell lung cancer developed hypophosphatemia (1.1 mg/dL) during chemotherapy. A reduced level of the tubular reabsorption of phosphate concomitant with an inappropriately elevated level of fibroblast growth factor (FGF) 23 (48.4 pg/mL) was noted, leading to the diagnosis of FGF23-related hypophosphatemia. Laboratory data also showed hypercortisolemia with an elevated ACTH level and hyponatremia with an inappropriately unsuppressed level of antidiuretic hormone (ADH). These data suggested the overproduction of FGF23 in addition to ACTH and ADH. Because the octreotide loading test did not present a suppressive effect on ACTH or FGF23 levels, the patient was treated with phosphate supplementation, active vitamin D and metyrapone, which partially improved the serum phosphate and cortisol levels. Even after two subsequent courses of chemotherapy, the small cell lung cancer progressed, and the FGF23 level was further elevated (83.7 pg/mL). Although it is very rare, FGF23-related hypophosphatemia is one of the hormonal disturbances that could be observed in patients with small cell lung cancer. This article reviews similar clinical conditions and revealed that advanced states of malignancy seemed to be associated with the development of renal wasting hypophosphatemia, especially in lung cancer and prostate cancer. Therefore, the parameters related to hypophosphatemia should be monitored in patients with advanced small cell lung cancer to prevent the development of hypophosphatemic osteomalacia.

Genetics of Diffuse Idiopathic Skeletal Hyperostosis and Ossification of the Spinal Ligaments

PURPOSE OF REVIEW

The study aims to provide updated information on the genetic factors associated with the diagnoses 'Diffuse Idiopathic Skeletal Hyperostosis' (DISH), 'Ossification of the Posterior Longitudinal Ligament' (OPLL), and in patients with spinal ligament ossification.

RECENT FINDINGS

Recent studies have advanced our knowledge of genetic factors associated with DISH, OPLL, and other spinal ossification (ossification of the anterior longitudinal ligament [OALL] and the yellow ligament [OYL]). Several case studies of individuals afflicted with monogenic disorders, such as X-linked hypophosphatemia (XLH), demonstrate the strong association of fibroblast growth factor 23-related hypophosphatemia with OPLL, suggesting that pathogenic variants in PHEX, ENPP1, and DMP1 are associated with FGF23-phosphate wasting phenotype and strong genetic factors placing patients at risk for OPLL. Moreover, emerging evidence demonstrates that heterozygous and compound heterozygous ENPP1 pathogenic variants inducing 'Autosomal Recessive Hypophosphatemic Rickets Type 2' (ARHR2) also place patients at risk for DISH and OPLL, possibly due to the loss of inhibitory plasma pyrophosphate (PPi) which suppresses ectopic calcification and enthesis mineralization. Our findings emphasize the importance of genetic and plasma biomarker screening in the clinical evaluation of DISH and OPLL patients, with plasma PPi constituting an important new biomarker for the identification of DISH and OPLL patients whose disease course may be responsive to ENPP1 enzyme therapy, now in clinical trials for rare calcification disorders.

Central odontogenic fibroma with amyloid: a diagnostically challenging case

Odontogenic fibroma is a rare benign mesenchymal odontogenic tumor, with its histological diversity possibly posing diagnostic challenges. A case of the amyloid variant of central odontogenic fibroma, with epithelial cells in perineural and intraneural locations, is reported herein. The 46-year-old female patient had experienced discomfort related to her anterior right hard palate for approximately 25 years. Clinical examination revealed a depression in the anterior hard palate, and radiographic examination showed a well-defined radiolucent lesion with root resorption of the adjacent teeth. Histologically, the well-circumscribed tumor was composed of hypocellular collagenous connective tissue with small islands of odontogenic epithelium. In addition, the juxta-epithelial deposition of amyloid globules without calcification and epithelial cells in perineural and intraneural locations were observed, which posed a diagnostic challenge in differentiating the lesion from the non-calcifying variant of calcifying epithelial odontogenic tumor and sclerosing odontogenic carcinoma. However, on the basis of the clinical and radiographic findings, which were suggestive of a benign and slowly progressive process given the corticated, unilocular radiolucency, the considerable root resorption, and the long history of this finding in an otherwise healthy patient, the final diagnosis was amyloid variant of central odontogenic fibroma. Increased recognition of this variant of odontogenic fibroma and its differentiation from other more aggressive lesions could help the clinician to avoid overdiagnosis and overtreatment.

A Novel Long Noncoding RNA in Osteocytes Regulates Bone Formation through the Wnt/β-Catenin Signaling Pathway

The vast majority of transcribed RNAs are noncoding RNAs. Among noncoding RNAs, long noncoding RNAs (lncRNAs), which contain hundreds to thousands of bases, have received attention in many fields. The vast majority of the constituent cells in bone tissue are osteocytes, but their regulatory mechanisms are incompletely understood. Considering the wide range of potential contributions of lncRNAs to physiological processes and pathological conditions, we hypothesized that lncRNAs in osteocytes, which have not been reported, could be involved in bone metabolism. Here, we first isolated osteocytes from femurs of mice with osteocyte-specific GFP expression. Then, through RNA-sequencing, we identified osteocyte-specific lncRNAs and focused on a novel lncRNA, 9530026P05Rik (lncRNA953Rik), which strongly suppressed osteogenic differentiation. In the IDG-SW3 osteocyte line with lncRNA953Rik overexpression, the expression of Osterix and its downstream genes was reduced. RNA pull-down and subsequent LC-MS/MS analysis revealed that lncRNA953Rik bound the nuclear protein CCAR2. We demonstrated that CCAR2 promoted Wnt/β-catenin signaling and that lncRNA953Rik inhibited this pathway. lncRNA953Rik sequestered CCAR2 from HDAC1, leading to deacetylation of H3K27 in the Osterix promoter and consequent transcriptional downregulation of Osterix. This research is the first to clarify the role of a lncRNA in osteocytes. Our findings can pave the way for novel therapeutic options targeting lncRNAs in osteocytes to treat bone metabolic diseases such as osteoporosis.

Recurrent bilateral adrenal infarction with myelodysplastic/myeloproliferative neoplasm-unclassifiable (MDS/MPN-U): a case report

BACKGROUND

Bilateral adrenal infarction is rare and only a small number of cases have been reported so far. Adrenal infarction is usually caused by thrombophilia or a hypercoagulable state, such as antiphospholipid antibody syndrome, pregnancy, and coronavirus disease 2019. However, adrenal infarction with myelodysplastic/myeloproliferative neoplasm (MDS/MPN) has not been reported.

CASE PRESENTATION

An 81-year-old man with a sudden severe bilateral backache presented to our hospital. Contrast-enhanced computed tomography (CT) led to the diagnosis of bilateral adrenal infarction. Previously reported causes of adrenal infarction were all excluded and a diagnosis of MDS/MPN-unclassifiable (MDS/MPN-U) was reached, which was considered to be attributed to adrenal infarction. He developed a relapse of bilateral adrenal infarction, and aspirin administration was initiated. Partial primary adrenal insufficiency was suspected as the serum adrenocorticotropic hormone level was persistently high after the second bilateral adrenal infarction.

CONCLUSION

This is the first case of bilateral adrenal infarction with MDS/MPN-U encountered. MDS/MPN has the clinical characteristics of MPN. It is reasonable to assume that MDS/MPN-U may have influenced bilateral adrenal infarction development, considering the absence of thrombosis history and a current comorbid hypercoagulable disease. This is also the first case of recurrent bilateral adrenal infarction. It is important to carefully investigate the underlying cause of adrenal infarction once adrenal infarction is diagnosed, as well as to assess adrenocortical function.

Patterns of symptoms and insufficiency fractures in patients with tumour-induced osteomalacia

The aim of this study was to report the patterns of symptoms and insufficiency fractures in patients with tumour-induced osteomalacia (TIO) to allow the early diagnosis of this rare condition. The study included 33 patients with TIO who were treated between January 2000 and June 2022. The causative tumour was detected in all patients. We investigated the symptoms and evaluated the radiological patterns of insufficiency fractures of the rib, spine, and limbs. The mean age of the patients was 57 years (24 to 87), and the mean duration of pain from onset to time of presentation was 3.9 years (0.75 to 23). The primary symptoms were low back pain (ten patients), chest wall pain (eight patients), and hip pain (eight patients). There were symptoms at more sites at the time of presentation compared with that at the time of the onset of symptoms. Bone scans showed the uptake of tracer in the rib (100%), thoracic and lumbar vertebrae (83%), proximal femur (62%), distal femur (66%), and proximal tibia (72%). Plain radiographs or MRI scans identified femoral neck fractures in 14 patients, subchondral insufficiency fractures of the femoral head and knee in ten and six patients, respectively, distal femoral fractures in nine patients, and proximal tibial fractures in 12 patients. Thoracic or lumbar vertebral fractures were identified in 23 of 29 patients (79.3%) when using any imaging study, and a biconcave deformity was the most common type of fracture. Insufficiency fractures in patients with TIO caused spinal pain, chest wall pain, and periarticular pain in the lower limbs. Vertebral fractures tended to be biconcave deformities, and periarticular fractures of the hips and knees included subchondral insufficiency fractures and epiphyseal or metaphyseal fractures. In patients with a tumour, the presence of one or more of these symptoms and an insufficiency fracture should suggest the diagnosis of TIO.

Intact Fibroblast Growth Factor 23 Concentrations in Hypophosphatemic Disorders

OBJECTIVE

Evaluation of circulating fibroblast growth factor 23 (FGF23) concentrations plays a key role in the differential diagnosis of patients presenting with hypophosphatemia. FGF23 concentrations obtained by different immunoassays are not comparable and subsequently, differences in the clinical performance of the assays might arise. In this study, we evaluated the clinical performance of the Medfrontier FGF23 Intact immunoassay (MedFrontier, Minaris Medical Co, Ltd, Tokyo, Japan) in clinically relevant hypophosphatemic conditions.

METHODS

Intact FGF23 (iFGF23) was measured in serum samples from 61 patients with FGF23-dependent hypophosphatemia (42-tumor induced osteomalacia [TIO] and 19-X-linked hypophosphatemia [XLH]); 8 patients with FGF23-independent hypophosphatemia (6-Fanconi Syndrome and 2-Vitamin D dependent rickets); 10 normophosphatemic patients; 15 chronic kidney disease (CKD) stage-2/3 and 20 CKD stage-4/5 patients; and a healthy control population. Disease-specific differences in measured iFGF23 concentrations and FGF23 concentration association with phosphate concentrations were reported.

RESULTS

iFGF23 concentrations were significantly elevated in 90% and 84% of TIO and XLH hypophosphatemia patients as compared to healthy controls (both TIO and XLH, P = .0001). There was no significant correlation between iFGF23 and phosphate concentrations (P = .74 and P = .86) for TIO and XLH, respectively. Patients with CKD showed a significant increase in serum iFGF23 as the estimated glomerular filtration rate decreased (ρ = -0.79, P ≤ 0.0001).

CONCLUSIONS

This study evaluated the clinical performance of the MedFrontier iFGF23 assay in a large cohort of XLH and TIO Caucasian and Asian patients. The clinical sensitivity of this iFGF23 assay is appropriate for clinical use.

Clinical performance of a new intact FGF23 immunoassay in healthy individuals and patients with chronic hypophosphatemia

While the positive association between automated intact fibroblast growth factor (FGF) 23 measurement kit (Determinar CL FGF23 [CL]) and the former assay (Kainos [KI]), and clinical utility of CL was well established, the clinical performance of Medfrontier FGF23 (MED), which was the manual intact FGF23 measurement kit with same antibody set as CL, has not yet been validated. Therefore, this study aims to compare MED FGF23 levels to KI FGF23 levels. A total of 380 samples were collected from healthy individuals, and 200 samples were collected from 20 patients with chronic hypophosphatemia. The intact FGF23 level of each sample was measured by KI and MED. Among the healthy individuals, the reference range of MED FGF23 levels was 18.6-59.8 pg/mL when calculated as the average ± 2 standard deviations. When compared with KI FGF23 levels, MED FGF23 levels were lower than KI levels both among samples from healthy individuals (KI FGF23, 40.9 [interquartile (IQR), 31.1-50.6]; MED FGF23, 38.0 [IQR, 31.5-45.7]; p value = 0.02) and among samples from patients with chronic hypophosphatemia (KI FGF23, 172.5 [IQR, 115.8-290.7]; MED FGF23, 130.2 [IQR, 93.6-247.0]; p value = 0.003). The linear regression analysis showed that the correlation between KI FGF23 and MED FGF23 was interpreted as a slope of 0.83 with a y-intercept of 0.53, revealing good linearity (R² = 0.99). This study showed that the discrepancy between KI and MED was very similar to the previously reported data between KI and CL.

Effect of conventional treatment on dental complications and ectopic ossifications among 30 adults with XLH

CONTEXT

Conventional treatment of XLH was reported to prevent dental complications, but whether the preventive effect was different among different types of teeth, including anterior teeth and molar teeth, is uncertain. Evidence of the preventive effect of conventional treatment on ectopic ossifications is also limited.

OBJECTIVE

To compare dental complications and ectopic ossifications among XLH adults with early (< 5 years old) or late (≥5 years old) conventional treatment.

METHODS

This retrospective observational study included a total of 30 adults with XLH using orthopantomograms, spinal computed tomography scans and X-rays of hip/knee joints. Dental complications, including decayed, missing filled (DMF) index and devitalized tooth, apical periodontitis, and periodontitis, were evaluated. The index of ossification of the anterior/posterior longitudinal ligament and yellow ligament (OA/OP/OY index) and the sum of the OA/OP/OY index (OS index) were utilized to evaluate the severity of spinal ligament ossification. The severity of the hip/knee osteophytes was evaluated by the Kellgren-Lawrence (KL) classification.

RESULTS

The number of sound teeth was significantly lower, and the DMF index was significantly higher in patients with late treatment. The severity of dental complications in the anterior tooth and molar tooth, OA/OP/OY/OS index, and KL grade were not significantly different among patients with early treatment and those with late treatment.

CONCLUSION

Early treatment could prevent dental complications but did not prevent ectopic ossification in adult patients with XLH. The difference in the preventive effect was not observed among different types of teeth.

Machine Learning-Based Prediction of Elevated PTH Levels Among the US General Population

CONTEXT

Although elevated parathyroid hormone (PTH) levels are associated with higher mortality risks, the evidence is limited as to when PTH is expected to be elevated and thus should be measured among the general population.

OBJECTIVE

This work aimed to build a machine learning-based prediction model of elevated PTH levels based on demographic, lifestyle, and biochemical data among US adults.

METHODS

This population-based study included adults aged 20 years or older with a measurement of serum intact PTH from the National Health and Nutrition Examination Survey (NHANES) 2003 to 2006. We used the NHANES 2003 to 2004 cohort (n = 4096) to train 6 machine-learning prediction models (logistic regression with and without splines, lasso regression, random forest, gradient-boosting machines [GBMs], and SuperLearner). Then, we used the NHANES 2005 to 2006 cohort (n = 4112) to evaluate the model performance including area under the receiver operating characteristic curve (AUC).

RESULTS

Of 8208 US adults, 753 (9.2%) showed PTH greater than 74 pg/mL. Across 6 algorithms, the highest AUC was observed among random forest (AUC [95% CI] = 0.79 [0.76-0.81]), GBM (AUC [95% CI] = 0.78 [0.75-0.81]), and SuperLearner (AUC [95% CI] = 0.79 [0.76-0.81]). The AUC improved from 0.69 to 0.77 when we added cubic splines for the estimated glomerular filtration rate (eGFR) in the logistic regression models. Logistic regression models with splines showed the best calibration performance (calibration slope [95% CI] = 0.96 [0.86-1.06]), while other algorithms were less calibrated. Among all covariates included, eGFR was the most important predictor of the random forest model and GBM.

CONCLUSION

In this nationally representative data in the United States, we developed a prediction model that potentially helps us to make accurate and early detection of elevated PTH in general clinical practice. Future studies are warranted to assess whether this prediction tool for elevated PTH would improve adverse health outcomes.

Utility of Multimodality Approach Including Systemic FGF23 Venous Sampling in Localizing Phosphaturic Mesenchymal Tumors

Context

Tumor-induced osteomalacia (TIO) is one of the most common forms of acquired fibroblast growth factor 23 (FGF23)-related hypophosphatemia and is usually caused by phosphaturic mesenchymal tumors (PMTs). Although the complete resection of PMTs can cure TIO, preoperative localization of tumors by standard imaging modalities is often challenging. In addition to ¹⁸F-fluoro-2-deoxy-D-glucose positron emission tomography-computed tomography (FDG-PET) and ¹¹¹In-pentetreotide scintigraphy (SRS), systemic FGF23 venous sampling (FGF23VS) has been used to help localize PMTs in specialized institutions.

Objective

This study aimed to evaluate the diagnostic performance of each imaging test and their combinations in localizing PMTs.

Methods

In an observational retrospective study of patients with adult-onset FGF23-related osteomalacia who underwent all 3 imaging studies (FDG-PET, SRS, and FGF23VS), the rate of successful preoperative localization of the tumors was evaluated only in the patients with pathological diagnoses of PMTs, considering the possibility that pathogenesis of patients without identified tumors might be due to other causes such as late-onset hereditary FGF23-related hypophosphatemia.

Results

A total of 30 Japanese patients with TIO (median age, 60 years [range, 28-87 years]; 10 women [33.3%]) were included in the study. The success rate of preoperative localization for each test and combinations of 2 or 3 tests among 18 patients with PMTs was as follows: 72% (FDG-PET), 72% (SRS), 94% (FGF23VS), 89% (FDG-PET, SRS), 100% (FDG-PET, FGF23VS), 94% (SRS, FGF23VS), and 100% (FDG-PET, SRS, and FGF23VS).

Conclusion

We observed the highest localization rate of PMTs in patients with identified PMTs with the combination of FDG-PET and FGF23VS.

The effect of burosumab on intact and C-terminal FGF23 measurements

OBJECTIVE

To investigate the effect of CRYSVITA® (burosumab-twza) on FGF23 measurements in an intact and a C-terminal immunoassay.

METHODS

An intact serum FGF23 (MedFrontier) and a C-terminal plasma FGF23 assay (Immutopics) were used. Serum/plasma pools were spiked to span the burosumab therapeutic range (1.4-11.3 μg/ml) and FGF23 recovery was assessed. Patient serum and plasma samples obtained pre and post-burosumab treatment were evaluated on both assays and compared with corresponding phosphorus measurements RESULTS: Spiking burosumab (1.4-11.3 μg/ml) into sample pools resulted in a dose-dependent negative analytical interference on intact FGF23 measurements and no significant interference for C-terminal FGF23 measurements. However, more than a 500-fold median increase (post- vs. pre-burosumab administration) in in vivo FGF23 concentrations were observed by both assays.

CONCLUSIONS

Therapeutic concentrations of burosumab result in a negative analytical interference of the intact, but not the C-terminal FGF23 immunoassay. Despite this in vitro analytical interference in the intact assay, relatively large elevations of both intact FGF23 and C-terminal FGF23 measurements were observed in vivo following burosumab administration. Following burosumab administration, FGF23 measurements must be interpreted within the clinical context of the patient and other relevant biomarker results.

SUMMARY

This article describes a negative analytical interference by burosumab in an intact FGF23 immunoassay. The recovery of C-terminal FGF23 is not significantly affected by the presence of burosumab. In vivo, both assays demonstrate extreme FGF23 elevations in the presence of the drug. Furthermore, the measurement of FGF23 blocked by burosumab is not clinically useful regarding hypophosphataemia.

Incidence of ossification of the spinal ligaments in acromegaly patients

Some previous case reports have implied a relationship between acromegaly and ossification of the spinal ligaments. However, there have been no reports of a case series exploring the incidence of ossification of the spinal ligaments in patients with acromegaly. To this end, computed tomography (CT) of the spine in 10 consecutive patients with acromegaly was examined in this study. Five out of 10 patients had ossification of the spinal ligaments. Among them, two patients had ossification of the posterior longitudinal ligament (OPLL), which was noticeably higher than the prevalence of OPLL in the general adult population (1.9–4.3 %). Body mass index was significantly higher in the group with spinal ligament ossification (p = 0.03), but there were no significant differences in age, sex, serum phosphate, albumin-adjusted calcium, growth hormone (GH), standard deviation of insulin-like growth factor-1 (IGF-1), or the incidence of diabetes mellitus between the groups with or without ossification of the spinal ligaments. The ossification index (OS index) was used to determine the severity of spinal ligament ossification, and there were no significant correlations between the OS index and GH or IGF-1 (p = 0.51 and 0.75, respectively). This study was the first to report a high prevalence of spinal ossification in patients with acromegaly. In conclusion, this study suggested a possible association between acromegaly and ossification of the spinal ligaments, although the number of patients was insufficient to draw a conclusion. Acromegaly patients should be tested to confirm, or rule out, spinal ossification, and further studies to clarify the underlying mechanism of spinal ossification in acromegaly patients are warranted.

Efficacy of Burosumab in Adults with X-linked Hypophosphatemia (XLH): A Post Hoc Subgroup Analysis of a Randomized Double-Blind Placebo-Controlled Phase 3 Study

The anti-fibroblast growth factor 23 monoclonal antibody burosumab corrects hypophosphatemia in adults with X-linked hypophosphatemia (XLH) and improves pain, stiffness, physical function, and fatigue. This post hoc subgroup analysis used data from the 24-week placebo-controlled period of a phase 3 study in 134 adults with XLH (ClinicalTrials.gov NCT02526160), to assess whether the benefits of burosumab are evident in 14 clinically relevant subgroups defined by baseline demographic and functional criteria, including sex, Brief Pain Inventory-short form (BPI-SF) Average And Worst Pain, region, race, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC®) Stiffness, Physical Function and Pain domains and total score, use of opioid/other pain medication, active fractures/pseudo-fractures, and 6-min walk test distance. There were no statistically significant interactions between any of the subgroups and treatment arm for any endpoint. Higher proportions of subjects achieved mean serum phosphate concentration above the lower limit of normal (the primary endpoint) with burosumab than with placebo in all subgroups. For the key secondary endpoints (WOMAC Stiffness and Physical Function; BPI-SF Worst Pain) individual subgroup categories showed improvements with burosumab relative to placebo. For additional efficacy endpoints, burosumab was favored in some subgroups but differences were not significant and confidence intervals were wide. For some endpoints the treatment effect is small at 24 weeks in all subjects. This subgroup analysis shows that burosumab was largely superior to placebo across endpoints in the 14 clinically relevant subgroup variables at 24 weeks and is likely to benefit all symptomatic adults with active XLH.

A Mild Case of Autosomal Recessive Osteopetrosis Masquerading as the Dominant Form Involving Homozygous Deep Intronic Variations in the CLCN7 Gene

Osteopetrosis is a heterogeneous group of rare hereditary diseases characterized by increased bone mass of poor quality. Autosomal-dominant osteopetrosis type II (ADOII) is most often caused by mutation of the CLCN7 gene leading to impaired bone resorption. Autosomal recessive osteopetrosis (ARO) is a more severe form and is frequently accompanied by additional morbidities. We report an adult male presenting with classical clinical and radiological features of ADOII. Genetic analyses showed no amino-acid-converting mutation in CLCN7 but an apparent haploinsufficiency and suppression of CLCN7 mRNA levels in peripheral blood mononuclear cells. Next generation sequencing revealed low-frequency intronic homozygous variations in CLCN7, suggesting recessive inheritance. In silico analysis of an intronic duplication c.595-120_595-86dup revealed additional binding sites for Serine- and Arginine-rich Splicing Factors (SRSF), which is predicted to impair CLCN7 expression. Quantitative backscattered electron imaging and histomorphometric analyses revealed bone tissue and material abnormalities. Giant osteoclasts were present and additionally to lamellar bone, and abundant woven bone and mineralized cartilage were observed, together with increased frequency and thickness of cement lines. Bone mineralization density distribution (BMDD) analysis revealed markedly increased average mineral content of the dense bone (CaMean T-score + 10.1) and frequency of bone with highest mineral content (CaHigh T-score + 19.6), suggesting continued mineral accumulation and lack of bone remodelling. Osteocyte lacunae sections (OLS) characteristics were unremarkable except for an unusually circular shape. Together, our findings suggest that the reduced expression of CLCN7 mRNA in osteoclasts, and possibly also osteocytes, causes poorly remodelled bone with abnormal bone matrix with high mineral content. This together with the lack of adequate bone repair mechanisms makes the material brittle and prone to fracture. While the skeletal phenotype and medical history were suggestive of ADOII, genetic analysis revealed that this is a possible mild case of ARO due to deep intronic mutation.

Improvement in Quality of Life via Catheter Ablation for Atrial Fibrillation in Patients Undergoing Hemodialysis Therapy

Background

Methods

Results

Conclusions

Clinical Challenges in Diagnosis, Tumor Localization and Treatment of Tumor-Induced Osteomalacia: Outcome of a Retrospective Surveillance

Tumor-induced osteomalacia (TIO) is an acquired fibroblast growth factor 23 (FGF23)-related hypophosphatemic osteomalacia caused by phosphaturic mesenchymal tumors (PMTs) developed in the bone or soft tissue. Diagnostic delay should be addressed, and ideal techniques to localize PMTs and efficient treatment options should be explored to improve the outcomes of this rare disease. To clarify the detailed clinical course and outcomes of TIO patients, retrospective questionnaire surveys were conducted among physicians from the Japanese Society for Bone and Mineral Research (JSBMR) and the Japan Endocrine Society (JES). The primary survey collected the number of TIO patients between January 2007 and December 2018. The secondary survey aimed to obtain the detailed characteristics, laboratory data, and outcomes. Eighty-eight patients (52 males, mean: 52 years old) were included, and 24 patients were clinically diagnosed with TIO without localized PMTs. The median duration from the onset to detection of high FGF23 levels was 3.4 years, with 77 patients being initially misdiagnosed. Among the methods used to detect small, localized PMTs (≤10 mm), fluorine-18-fluorodeoxyglucose-positron emission tomography/computed tomography and somatostatin receptor scintigraphy were less sensitive than somatostatin receptor positron emission tomography/computed tomography (SRPET/CT). Systemic venous sampling (SVS) of FGF23 was performed in 53 patients; among them, SVS was considered useful for detecting localized PMTs in 45 patients with diverse tumor sizes. Finally, 45 patients achieved biochemical remission by surgery, 39 patients continued pharmaceutical treatment, including burosumab (11 patients), and four patients died. These results encouraged us to further increase the awareness of TIO and to improve the accessibility of SRPET/CT and SVS. Further evidence about the efficacy of new pharmaceutical treatments is awaited. © 2022 American Society for Bone and Mineral Research (ASBMR).

Radiological evaluation of pseudofracture after the administration of asfotase alfa in an adult with benign prenatal hypophosphatasia: A case report

Hypophosphatasia (HPP) is a congenital disorder with decreased activity of tissue-nonspecific alkaline phosphatase. Asfotase alfa is the only treatment approved for HPP and improves the impairment of bone mineralization. Although several previous studies have reported the efficacy of asfotase alfa to treat fractures and pseudofractures in patients with HPP, there are only a few reports with a detailed description of the healing process. In this case report, we present an 18-year-old female patient with benign prenatal HPP who received asfotase alfa to treat her pseudofracture. At the age of 17, a pseudofracture developed in her left tibia after repetitive gymnastic exercise for months. Following observation over a year, she was referred to our department. X-ray images indicated a narrow radiolucent band in the mid-diaphysis of her left tibia, and bone scintigraphy showed nuclide accumulation in the same region. Replacement therapy with asfotase alfa was started, resulting in pain relief in two months, and the disappearance of nuclide accumulation on bone scintigraphy and union of the pseudofracture on X-ray after two years. This is the first case report describing the detailed pseudofracture healing process in a patient with benign prenatal HPP initiating asfotase alfa.

Identification of ENPP1 Haploinsufficiency in Patients With Diffuse Idiopathic Skeletal Hyperostosis and Early-Onset Osteoporosis

Homozygous ENPP1 mutations are associated with autosomal recessive hypophosphatemic rickets type 2 (ARHR2), severe ossification of the spinal ligaments, and generalized arterial calcification of infancy type 1. There are a limited number of reports on phenotypes associated with heterozygous ENPP1 mutations. Here, we report a series of three probands and their families with heterozygous and compound heterozygous ENPP1 mutations. The first case (case 1) was a 47-year-old male, diagnosed with early-onset osteoporosis and low-normal serum phosphate levels, which invoked suspicion for hypophosphatemic rickets. The second and third cases were 77- and 54-year-old females who both presented with severe spinal ligament ossification and the presumptive diagnosis of diffuse idiopathic skeletal hyperostosis (DISH). Upon workup, fibroblast growth factor 23 (FGF23) was noted to be relatively high in case 2 and serum phosphorous was low-normal in case 3, and the diagnoses of X-linked hypophosphatemic rickets (XLH) and ARHR2 were considered. Genetic testing for genes related to congenital hypophosphatemic rickets was therefore performed, revealing heterozygous ENPP1 variants in cases 1 and 2 (case 1, c.536A>G, p.Asn179Ser; case 2, c.1352A>G, p.Tyr451Cys) and compound heterozygous ENPP1 variants in case 3 constituting the same variants present in cases 1 and 2 (c.536A>G, p.Asn179Ser and c.1352A>G, p.Tyr451Cys). Several in silico tools predicted the two variants to be pathogeneic, a finding confirmed by in vitro biochemical analysis demonstrating that the p.Asn179Ser and p.Tyr451Cys ENPP1 variants possessed a catalytic velocity of 45% and 30% compared with that of wild-type ENPP1, respectively. Both variants were therefore categorized as pathogenic loss-of-function mutations. Our findings suggest that ENPP1 mutational status should be evaluated in patients presenting with the diagnosis of idiopathic DISH, ossification of the posterior longitudinal ligament (OPLL), and early-onset osteoporosis. © 2022 American Society for Bone and Mineral Research (ASBMR).

Burden of disease of X-linked hypophosphatemia in Japanese and Korean patients: a cross-sectional survey

The burden of disease of X-linked hypophosphatemia (XLH) in East Asia is poorly understood. This was a cross-sectional study using an online questionnaire to evaluate health-related quality of life (HRQOL) and disease complications in Japanese and Korean patients with XLH. Adults with XLH and the caregivers of children <18 years of age with XLH in Japan and Korea were surveyed. Respondents disclosed demographic data, family history, diagnostic history, medical history, surgical history, disease-specific clinical symptoms, treatment, medications, and use of ancillary equipment. Patient-reported outcomes (PROs; the Western Ontario and McMaster Universities Osteoarthritis Index, the brief pain inventory, and the 36-item short form health survey version 2) were used to assess pain, disability, and HRQOL in adults. Of those surveyed, all 14 children (100%) and 30/32 adults (93.8%) were receiving treatment for XLH. However, despite oral phosphate and active vitamin D use, short stature, gait abnormalities, dental conditions, and decreased physical function were reported. Stapling of the growth plates was reported in 14.3% of children but no adults. Adult patients reported high rates of bone pain (59.4%) and joint pain (65.6%). Caregivers of children with XLH also reported the occurrence of bone pain (35.7%) and joint pain (35.7%). Many adult patients had a history of impaired renal function (9.5%), nephrocalcinosis (15.6%), hyperparathyroidism (15.6%), and parathyroidectomy (6.3%), all of which are associated with conventional XLH treatments. These data show that patients (both pediatric and adult) continue to have symptoms such as pain, disability, and various complications despite receiving conventional therapies.

Hemodynamic Collapse Caused by Cardiac Dysfunction and Abdominal Compartment Syndrome in a Patient with Mitochondrial Disease

We herein report a case of mitochondrial disease with heart and intestinal tract involvement resulting in hemodynamic collapse. A 66-year-old woman was transferred to our hospital because of cardiogenic shock. Vasopressors were administered, and a circulatory support device was deployed. However, her hemodynamics did not improve sufficiently, and we detected abdominal compartment syndrome caused by the aggravation of chronic intestinal pseudo-obstruction as a complication. Insertion of a colorectal tube immediately decreased the intra-abdominal pressure, improving the hemodynamics. Finally, we diagnosed her with mitochondrial disease, concluding that the resulting combination of acute heart failure and abdominal compartment syndrome had aggravated the hemodynamics.

Massive calcification around large joints in a patient subsequently diagnosed with adult-onset hypophosphatasia

We report a 64-year-old Japanese woman with a history of progressive loss of motor function and painful swelling of large joints. At the age of 54, profound calcification appeared around the shoulder and hip joints, which did not heal after repeated surgical resections. Iliac bone biopsy revealed osteomalacic changes. Laboratory data showed low serum alkaline phosphatase (ALP) activity and a high urine phosphoethanolamine (PEA) concentration with normal serum calcium, phosphate, and fibroblast growth factor 23 (FGF23) levels. Subsequent genetic analysis of the ALPL gene confirmed the diagnosis of hypophosphatasia (HPP) with the identification of a heterozygous single nucleotide deletion, c.1559delT (p.Leu520ArgfsX86). We started a mineral-targeted enzyme replacement therapy, asfotase alfa (AA), to treat the patient's musculoskeletal symptoms. A follow-up bone biopsy after 12 months of AA treatment showed improvement of osteomalacia. Calcified deposits around the large joints were unchanged radiographically. To our knowledge, this is the first report of a patient with an adult-onset HPP who presented with profound calcification around multiple joints. Nonspecific clinical signs and symptoms in patients with adult-onset HPP often result in delayed diagnosis or misdiagnosis. We propose that bone biopsy and genetic analysis should be considered along with laboratory analysis for all patients with ectopic calcification around joints of unknown etiology for accurate diagnosis and better treatment.

Performance evaluation of the new chemiluminescent intact FGF23 assay relative to the existing assay system

INTRODUCTION

This study assessed the performance of a new fully automated immunoassay for fibroblast growth factor (FGF) 23 (Determinar CL FGF23 CL) among healthy individuals and those with chronic hypophosphatemia compared with the previous assay (Kainos FGF23 KI).

MATERIALS AND METHODS

A total of 380 serum samples from healthy participants were collected to determine the reference range of FGF23 levels with CL. A total of 200 serum samples from 22 hypophosphatemic patients were collected simultaneously to compare the difference in FGF23 levels between CL and KI. The Mann-Whitney U test and linear regression analysis were adopted to assess the differences and linearity between the two assays.

RESULTS

The median FGF23 levels among healthy individuals was 31.7 (interquartile: 26.4-37.5) pg/mL. When the reference range was calculated as the mean  ± 2 standard deviation (2SD), it was 16.1-49.3 pg/mL. A total of 363 individuals (96%) among normal cases fell in this range. Among 200 samples from patients with chronic hypophosphatemic disorder, the median FGF23 levels analyzed by CL and KI were 123.0 (90.2-237.7) and 172.5 (115.8-290.7) pg/mL. KI yielded significantly higher FGF23 values than CL (p < 0.001). A linear regression model revealed the correlation between KI (x) and CL (y), which had a slope of 0.76 with a y-intercept of -0.32 and high linearity (R² = 0.99).

CONCLUSION

The new measurement kit yielded lower FGF23 values when compared with the previous assay. Clinicians should consider this discrepancy when they assay intact FGF23 values with CL.

Clinical performance of a novel chemiluminescent enzyme immunoassay for FGF23

INTRODUCTION

Measurement of fibroblast growth factor 23 (FGF23) has been reported to be clinically useful for the differential diagnosis of chronic hypophosphatemia. However, assays for research use only are available in Japan. Thus, the objective of this study was to examine the clinical utility of a novel and automated chemiluminescent enzyme immunoassay for the measurement of FGF23.

MATERIALS AND METHODS

Participants were recruited from July 2015 to January 2017 at six facilities in Japan. Thirty-eight patients with X-linked hypophosphatemic rickets (XLH 15 males, 23 females, age 0-66 years), five patients with tumour-induced osteomalacia (TIO 3 males, 2 females, age 60-73 years), and twenty-two patients with hypophosphatemia (11 males, 11 females, age 1-75 years) caused due to other factors participated in this study.

RESULTS

With the clinical cut-off value of FGF23 at 30.0 pg/mL indicated in the Diagnostic Guideline of Rickets/Osteomalacia in Japan, the sensitivity and specificity of FGF23-related hypophosphatemic rickets/osteomalacia without vitamin D deficiency (disease group-1) were 100% and 81.8%, respectively, which distinguished it from non-FGF23-related hypophosphatemia (disease group-2). Furthermore, the diagnostic sensitivity of FGF23-related hypophosphatemia with vitamin D deficiency remained at 100%. Among the four patients with FGF23 levels ≥ 30.0 pg/mL in disease group-2, two patients with relatively higher FGF23 values were suspected to have genuine FGF23-related hypophosphatemia, due to the ectopic production of FGF23 in pulmonary and prostate small cell carcinomas.

CONCLUSION

The novel FGF23 assay tested in this study is useful for the differential diagnosis of hypophosphatemic rickets/osteomalacia in a clinical setting.

Burosumab treatment in adults with X-linked hypophosphataemia: 96-week patient-reported outcomes and ambulatory function from a randomised phase 3 trial and open-label extension

Objectives

To report the impact of burosumab on patient-reported outcomes (PROs) and ambulatory function in adults with X-linked hypophosphataemia (XLH) through 96 weeks.

Methods

Adults diagnosed with XLH were randomised 1:1 in a double-blinded trial to receive subcutaneous burosumab 1 mg/kg or placebo every 4 weeks for 24 weeks (NCT02526160). Thereafter, all subjects received burosumab every 4 weeks until week 96. PROs were measured using the Western Ontario and the McMaster Universities Osteoarthritis Index (WOMAC), Brief Pain Inventory-Short Form (BPI-SF) and Brief Fatigue Inventory (BFI), and ambulatory function was measured with the 6 min walk test (6MWT).

Results

Subjects (N=134) were randomised to burosumab (n=68) or placebo (n=66) for 24 weeks. At baseline, subjects experienced pain, stiffness, and impaired physical and ambulatory function. At week 24, subjects receiving burosumab achieved statistically significant improvement in some BPI-SF scores, BFI worst fatigue (average and greatest) and WOMAC stiffness. At week 48, all WOMAC and BPI-SF scores achieved statistically significant improvement, with some WOMAC and BFI scores achieving meaningful and significant change from baseline. At week 96, all WOMAC, BPI-SF and BFI achieved statistically significant improvement, with selected scores in all measures also achieving meaningful change. Improvement in 6MWT distance and percent predicted were statistically significant at all time points from 24 weeks.

Conclusions

Adults with XLH have substantial burden of disease as assessed by PROs and 6MWT. Burosumab treatment improved phosphate homoeostasis and was associated with a steady and consistent improvement in PROs and ambulatory function.

Trial registration number

NCT02526160.

Surgical margin for phosphaturic mesenchymal tumors in soft tissues: An analysis of the radiological histopathological correlation

BACKGROUND

Phosphaturic mesenchymal tumors primarily cause tumor-induced osteomalacia, a rare paraneoplastic syndrome, and half occur in soft tissues. There are few reports about the surgical margins of these tumors. This study aimed to clarify the optimal surgical margin for phosphaturic mesenchymal tumors by analyzing radiological and histopathological features.

METHODS

This study included eight cases, seven primary and one recurrent, of tumor-induced osteomalacia caused by soft-tissue phosphaturic mesenchymal tumors that were surgically treated between January 2000 and January 2019. We evaluated the radiological and histopathological features of all tumors and investigated the correlation of these features, the surgical margin, and recurrence of hypophosphatemia.

RESULTS

The tumors were located in superficial (n = 5) and deep (n = 3) tissues. Six of the eight tumors had a clear boundary, but five had an irregular margin. Three tumors had a hypointense rim on T2-weighted images, indicating fibrous tumor encapsulation. Histopathological analysis revealed infiltrative growth in six of the eight tumors, which correlated with an irregular margin seen on imaging. Although there was no recurrence in patients treated with an intended wide margin >1 cm, one of the three patients treated with marginal tumor resection experienced a recurrence of hypophosphatemia, with histopathological analysis showing infiltration of subcutaneous fat. In contrast, two tumors with clear boundaries, regular margins, and fibrous capsule seen on imaging, had no infiltrative growth and were cured by marginal resection. In one recurrent case, tumor infiltration was observed in the previous surgical scar, which was not detected on preoperative imaging.

CONCLUSIONS

Soft-tissue phosphaturic mesenchymal tumors with an irregular boundary seen on imaging tend to be infiltrative, especially into subcutaneous fat, and should be treated by at least a 1-cm wide margin resection. Tumors with a fibrous capsule with clear and regular margins are cured by marginal margin resection. These findings could inform surgeons' decisions regarding the resection of soft-tissue phosphaturic mesenchymal tumors.

Incidence of Complications in 25 Adult Patients With X-linked Hypophosphatemia

CONTEXT

Adults with X-linked hypophosphatemia (XLH) present complications other than osteomalacia.

OBJECTIVE

To describe the incidence and severity of comorbidities in adults with XLH.

METHODS

This observational retrospective study included a total of 25 adults with XLH with thorough investigations, including spinal computed tomography scans, x-rays of hip/knee joints and Achilles tendons, abdominal ultrasounds, and audiograms. The index of ossification of the anterior/posterior longitudinal ligament and yellow ligament (OA/OP/OY index) and the sum of OA/OP/OY index (OS index) were utilized to evaluate the severity of spinal ligament ossification. The Kellgren-Lawrence (KL) classification was adopted to evaluate the severity of the hip/knee osteophytes.

RESULTS

The participants consisted of 13 male patients and 12 female patients from 21 families, with a median age of 43 (range, 18-72) years. In all, 20 patients (80%) showed spinal ligament ossification. The median OA/OP/OY/OS indices were 2 (0-22), 0 (0-15), 6 (0-13), and 12 (0-41), respectively. Hip/knee osteophytes were reported in 24 (96%) and 17 cases (68%). The median KL grade was 3 in the hip joint and 2 in the knee joint, and 18 cases (72%) developed enthesopathy in the Achilles tendon. Nephrocalcinosis and hearing impairment were observed in 18 (72%) and 8 (32%) cases.

CONCLUSION

This study revealed a high prevalence and severity of ectopic ossification and disclosed the incidence of nephrocalcinosis and hearing impairment in adults with XLH. In cases with severe spinal ligament ossification or noticeable osteophytes around the hip/knee joints, undiagnosed XLH should be considered as a possible underlying condition.

Gastrointestinal stromal tumour lacking mutations in the KIT and PDGFRA genes in a cat

Molecular subtyping in gastrointestinal stromal tumours is a useful method for predicting the efficacy of treatment using tyrosine kinase inhibitors in humans. However, owing to the paucity of reports on mutational analyses, the association between genetic mutations and the therapeutic response to tyrosine kinase inhibitors remains unclear in feline gastrointestinal stromal tumours. In this report, we describe the case of a cat with a gastrointestinal stromal tumour which was unresponsive to tyrosine kinase inhibitors. A mutational analysis revealed that the cat lacked mutations in both the KIT and platelet-derived growth factor receptor-alpha (PDGFRA) genes. Our findings are consistent with the fact that KIT/PDGFRA wild-type gastrointestinal stromal tumours are less responsive to tyrosine kinase inhibitors in humans. This signifies the need for further evaluation and possibly individualised treatment for gastrointestinal stromal tumours in cats on the basis of mutational analyses.

Sclerostin Directly Stimulates Osteocyte Synthesis of Fibroblast Growth Factor-23

Osteocyte produced fibroblast growth factor 23 (FGF23) is the key regulator of serum phosphate (Pi) homeostasis. The interplay between parathyroid hormone (PTH), FGF23 and other proteins that regulate FGF23 production and serum Pi levels is complex and incompletely characterised. Evidence suggests that the protein product of the SOST gene, sclerostin (SCL), also a PTH target and also produced by osteocytes, plays a role in FGF23 expression, however the mechanism for this effect is unclear. Part of the problem of understanding the interplay of these mediators is the complex multi-organ system that achieves Pi homeostasis in vivo. In the current study, we sought to address this using a cell line model of the osteocyte, IDG-SW3, known to express FGF23 at both the mRNA and protein levels. In cultures of differentiated IDG-SW3 cells, both PTH_1-34 and recombinant human (rh) SCL remarkably induced Fgf23 mRNA expression dose-dependently within 3 h. Both rhPTH_1-34 and rhSCL also strongly induced C-terminal FGF23 protein secretion. Secreted intact FGF23 levels remained unchanged, consistent with constitutive post-translational cleavage of FGF23 in this cell model. Both rhPTH_1-34 and rhSCL treatments significantly suppressed mRNA levels of Phex, Dmp1 and Enpp1 mRNA, encoding putative negative regulators of FGF23 levels, and induced Galnt3 mRNA expression, encoding N-acetylgalactosaminyl-transferase 3 (GalNAc-T3), which protects FGF23 from furin-like proprotein convertase-mediated cleavage. The effect of both rhPTH_1-34 and rhSCL was antagonised by pre-treatment with the NF-κβ signalling inhibitors, BAY11 and TPCK. RhSCL also stimulated FGF23 mRNA expression in ex vivo cultures of human bone. These findings provide evidence for the direct regulation of FGF23 expression by sclerostin. Locally expressed sclerostin via the induction of FGF23 in osteocytes thus has the potential to contribute to the regulation of Pi homeostasis.

Primary bone adult T cell lymphoma with multiple skeletal lesions and debilitating painful osteolysis: a case report

There have been only a limited number of reports on primary adult T cell lymphoma/leukemia (ATL) in the bone. This is a case report of a 75-year-old patient initially reporting multiple bone pains that were attributed to osteolytic ATL. The patient developed spontaneous chest/back pain and visited a local hospital. Laboratory tests showed high levels of alkaline phosphatase (ALP), and computed tomography (CT) revealed skeletal lesions with osteolysis. Although multiple myeloma was initially suspected, the results of bone marrow aspiration and bone biopsy were inconsistent. After he was referred to our hospital, mild hypercalcemia (10.4 mg/dL) with low-normal intact parathyroid hormone (PTH) (27 pg/mL), low parathyroid hormone-related protein (PTHrP), and elevated 1,25-dihydroxy vitamin D (1,25OH₂D) levels (136 pg/mL) narrowed the differential diagnosis down to lymphomatous and granulomatous diseases, and then, the high serum soluble IL-2 receptor (3,450 U/mL) and the flower cells recognized in the peripheral blood sample suggested the involvement of ATL. Finally, the reevaluation of the iliac bone biopsy sample led us to the histological diagnosis of ATL infiltration in the bone. The subsequent two courses of chemotherapy in addition to denosumab resulted in an objective partial metabolic response indicated in 18-fluorine-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT). Although very rare, the bone involvement of ATL could be used for the differential diagnosis for local osteolytic bone pain in addition to multiple myeloma and metastatic bone diseases.

Comparison of traditional two-injection dorsal digital block versus transthecal and subcutaneous single-injection digital block: A systematic review and meta-analysis

Digital nerve block is a common procedure with several techniques, including the traditional digital nerve block, transthecal digital nerve block, and single subcutaneous palmar digital nerve block. This review aimed to evaluate the efficacy of these three methods. A systematic search was performed in the PubMed, Scopus, and Cochrane Library databases. The risk of bias of the studies was assessed using the Cochrane Collaboration's tool for assessing the risk of bias and the Risk of Bias Assessment Tool for Non-Randomized Studies. Fourteen prospective randomized controlled studies and one prospective comparative study were included. The three methods of digital block showed similar onset times, durations, injection pain and incidence of incomplete anesthesia. This review confirmed that all three methods of digital block are equally effective. Considering that patients prefer a single injection and the potential risk of complications, the single subcutaneous digital block could be more widely used.

Interim Analysis of a Phase 2 Open-Label Trial Assessing Burosumab Efficacy and Safety in Patients With Tumor-Induced Osteomalacia

Patients with tumor-induced osteomalacia (TIO), an acquired paraneoplastic condition characterized by osteomalacia due to hypophosphatemia, exhibit a similar clinical picture to those with X-linked hypophosphatemic rickets/osteomalacia (XLH). The human monoclonal anti-fibroblast growth factor 23 (FGF23) antibody burosumab (KRN23) increases serum phosphate and improves bone turnover, fracture healing, pain, and physical function in XLH patients by inhibiting circulating FGF23; thus, burosumab is expected to be an effective treatment for TIO. We report here an interim analysis of a multicenter, open-label, intraindividual dose-adjustment study of burosumab (0.3 to 2.0 mg/kg every 4 weeks) in Japanese and Korean TIO patients. The primary endpoint was the fasting serum phosphate level at each visit. Key secondary endpoints were changes over time in bone biomarkers, pharmacodynamic markers, bone histomorphometric parameters, motor function, and patient-reported outcomes. Safety was assessed based on treatment-emergent adverse events (TEAEs). Thirteen patients received burosumab treatment, of whom 4 underwent bone biopsy. The mean dose after week 112 was approximately 1.0 mg/kg. After the first burosumab administration, mean serum phosphate levels increased and remained above the lower limit of normal and in the normal range from weeks 14 to 112. Bone biomarkers initially increased, reaching maximum values at week 16 or 24, and then gradually decreased. After burosumab treatment, patients were able to walk further (evaluated by the 6-minute walk test), reported decreased pain levels, and showed a tendency toward healing of baseline fractures and pseudofractures. Two patients discontinued, one each due to disease progression and consent withdrawal. Burosumab was generally well tolerated, with no treatment-related TEAEs of grade ≥3 and no treatment-related serious AEs. In conclusion, the interim results of this first study of burosumab to treat TIO patients indicate that this drug has the potential to provide clinical benefit for patients with unresectable tumors. The full study results are eagerly anticipated. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR)..

Congenital Hyperphosphatemic Conditions Caused by the Deficient Activity of FGF23

Congenital diseases that could result in hyperphosphatemia at an early age include hyperphosphatemic familial tumoral calcinosis (HFTC)/hyperostosis-hyperphosphatemia syndrome (HHS) and congenital hypoparathyroidism/pseudohypoparathyroidism due to the insufficient activity of fibroblast growth factor (FGF) 23 and parathyroid hormone. HFTC/HHS is a rare autosomal recessive disease caused by inactivating mutations in the FGF23, UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3), or Klotho (KL) genes, resulting in the excessive cleavage of active intact FGF23 (FGF23, GALNT3) or increased resistance to the action of FGF23 (KL). Massive ectopic calcification, known as tumoral calcinosis (TC), is seen in periarticular soft tissues, typically in the hip, elbow, and shoulder in HFTC/HHS, reducing the range of motion. However, other regions, such as the eye, intestine, vasculature, and testis, are also targets of ectopic calcification. The other symptoms of HFTC/HHS are painful hyperostosis of the lower legs, dental abnormalities, and systemic inflammation. Low phosphate diets, phosphate binders, and phosphaturic reagents such as acetazolamide are the treatment options for HFTC/HHS and have various consequences, which warrant the development of novel therapeutics involving recombinant FGF23.

Altered Thyroid Function Tests Observed in Hypophosphatasia Patients Treated with Asfotase Alfa

BACKGROUND

Asfotase alfa is the only approved treatment that can normalize mineralization in patients with hypophosphatasia (HPP). Its interference in alkaline phosphatase (ALP) dependent immunoassays has been reported.

OBJECTIVE

To describe thyroid function tests interfered with by asfotase alfa and elucidate the underlying mechanism. Patients and Methods. Three patients with HPP treated with asfotase alfa were included. Thyroid hormone levels measured using five different immunoassays with or without ALP as a labeling enzyme during asfotase alfa treatment were evaluated.

RESULTS

After the initiation of asfotase alfa, three HPP patients showed low free triiodothyronine (FT3) and free thyroxine (FT4) measured with AIA-2000 (Tosoh, Tokyo, Japan), an enzyme immunoassay system that uses ALP as a labeling enzyme, but their thyroid-stimulating hormone (TSH) levels were within the normal range. The other CLEIA system using ALP as a label, AIA-CL2400 (Tosoh, Tokyo, Japan), and ALP-independent immunoassay systems demonstrated normal FT3 and FT4 levels. These data suggested that although the thyroid function of these three patients was normal, asfotase alfa interfered with the thyroid hormone measurements made with AIA-2000. AIA-2000 and AIA-CL2400 adopted one-step and delayed one-step measurements, respectively, and the same antibody was used for both immunoassays. However, asfotase alfa may be absorbed on the magnetic beads used in the AIA reagent with the AIA-2000 system but not absorbed on the microparticles used in AIA-CL2400.

CONCLUSION

Clinicians should be aware of the possible interference in thyroid function measurements by adopting specific types of immunoassays in asfotase alfa-treated HPP patients.

Prognostic value of cardiac 123I-metaiodobenzylguanidine imaging for predicting cardiac events after transcatheter aortic valve replacement

Background

In patients with aortic valve stenosis (AS), cardiac sympathetic nervous (CSN) dysfunction and its improvement after TAVR have been reported; however, the prognostic impact of CSN function remains unclear. This study investigated the prognostic value of cardiac 123I-metaiodobenzylguanidine (MIBG) imaging for the prediction of cardiac events after transcatheter aortic valve replacement (TAVR).

Methods

This study was a single-center prospective observational study that enrolled patients with AS or failed surgical bioprostheses between July 2017 and May 2019. MIBG scintigraphy was performed before and after TAVR to evaluate the delayed heart–mediastinum ratio (d-H/M). Patients were classified into three pairs of groups based on the baseline and post-TAVR d-H/M (≥2.0 or &lt;2.0) and on the presence of TAVR-related improvement of d-H/M. The study endpoints were major adverse cardiac events (MACE), including all-cause death, myocardial infarction, and hospitalization due to heart failure. The association of d-H/M with MACE following TAVR was based on a Cox proportional hazards ratio model adjusted for multiple prognostic variables.

Results

Of 187 consecutive patients who underwent TAVR, 111 (31 men; median age: 86 years) were evaluated. Over a median follow-up of 366 days, 16 (14.4%) patients had MACE. The incidence of MACE was significantly lower in patients with d-H/M improvement and/or the high post-TAVR d-H/M (≥2.0). Post-TAVR d-H/M had significant impacts on MACE, with an adjusted hazard ratio of 1.326 (95% confidence interval, 0.139–2.515; p=0.027).

Conclusions

Both d-H/M improvement and high post-TAVR d-H/M were associated with better prognosis in patients who underwent TAVR. Cardiac MIBG imaging was useful for predicting cardiac events after TAVR.

Funding Acknowledgement

Type of funding source: None