Emerging Role of Gallium-68 DOTANOC PET/CT Guided Radiofrequency Ablation in the Treatment of Tumor-induced Osteomalacia

Tumor-induced osteomalacia (TIO) is a rare acquired form of hypophosphatemia that can be cured when the tumor responsible is completely removed. These tumors can be small and located in anatomically challenging areas, rendering surgery both risky and extensive. Radiofrequency ablation (RFA) has been explored as an effective treatment option for such tumors. We present a case of a 35-year-old man exhibiting clinical and biochemical features consistent with TIO. The culprit lesion was not detectable on the whole-body computed tomography (CT) scan. Gallium (Ga-68) DOTANOC positron emission tomography (PET)/CT showed increased uptake in the left acetabulum and magnetic resonance imaging (MRI) confirmed the location of the tumor. Given the risky anatomical location, we opted for less-invasive RFA. Following an unsuccessful attempt at CT-guided RFA of the lesion, we used real-time Ga-68 DOTANOC PET/CT guidance for precise imaging during the ablation procedure. Our patient achieved complete remission both clinically and biochemically after RFA. This response was also evident by the absence of tracer uptake in follow-up imaging. In conclusion, DOTANOC PET/CT-guided RFA can serve as a safe and effective treatment for patients with tumors causing TIO. This modality proves valuable when surgical resection is not a viable option.

Acquired disorders of phosphaturia: Beyond tumor-induced osteomalacia

Phosphate is an integral part of human cellular structure and function. Though most recognised disorders of phosphaturia are genetic in origin, phosphate loss due to acquired conditions is commonly encountered in clinical practice. Acquired hypophosphatemia is most commonly due to renal phosphate wasting and can produce significant morbidity. It also heralds future kidney damage, and continued exposure can lead to progressive kidney injury and potentially renal failure. These conditions are a diverse group of disorders with common shared mechanisms causing loss of phosphate in the urine. Renal phosphate loss can occur as an isolated entity or as a part of generalised proximal tubular dysfunction, i.e., Fanconi's syndrome. An insight into the pathophysiological mechanisms of acquired phosphaturia can help clinicians monitor their patients better and avoid potential harms.

Inherited non-FGF23-mediated phosphaturic disorders: A kidney-centric review

Phosphate is freely filtered by the glomerulus and reabsorbed exclusively in the proximal tubule by two key transporters, NaPiIIA and NaPiIIC, encoded by SLC34A1 and SLC34A3, respectively. Regulation of these transporters occurs primarily through the hormone FGF23 and, to a lesser degree, PTH. Consequently, inherited non-FGF23 mediated phosphaturic disorders are due to generalised proximal tubular dysfunction, loss-of-function variants in SLC34A1 or SLC34A3 or excess PTH signalling. The corresponding disorders are Renal Fanconi Syndrome, Infantile Hypercalcaemia type 2, Hereditary Hypophosphataemic Rickets with Hypercalciuria and Familial Hyperparathyroidism. Several inherited forms of Fanconi renotubular syndrome (FRTS) have also been described with the underlying genes encoding for GATM, EHHADH, HNF4A and NDUFAF6. Here, we will review their pathophysiology, clinical manifestations and the implications for treatment from a kidney-centric perspective, focussing on those disorders caused by dysfunction of renal phosphate transporters. Moreover, we will highlight specific genetic aspects, as the availability of large population genetic databases has raised doubts about some of the originally proposed gene-disease associations concerning phosphate transporters or their associated proteins.

Fibroblast Growth Factor 23 Neutralizing Antibody Ameliorates Abnormal Renal Phosphate Handling in Sickle Cell Disease Mice

We assessed the involvement of fibroblast growth factor 23 (FGF23) in phosphaturia in sickle cell disease (SCD) mice. Control and SCD mice were treated with FGF23 neutralizing antibody (FGF23Ab) for 24 hours. Serum ferritin was significantly increased in SCD mice and was significantly reduced in female but not male SCD mice by FGF23Ab. FGF23Ab significantly reduced increased erythropoietin in SCD kidneys. Serum intact FGF23 was significantly increased in SCD female mice and was markedly increased in SCD male mice; however, FGF23Ab significantly reduced serum intact FGF23 in both genotypes and sexes. Serum carboxy-terminal-fragment FGF23 (cFGF23) was significantly reduced in SCD IgG male mice and was markedly but not significantly reduced in SCD IgG female mice. FGF23Ab significantly increased cFGF23 in both sexes and genotypes. Serum 1,25-dihydroxyvitamin D3 was significantly increased in SCD IgG and was further significantly increased by FGF23Ab in both sexes and genotypes. Significantly increased blood urea nitrogen in SCD was not reduced by FGF23Ab. The urine phosphate (Pi)/creatinine ratio was significantly increased in SCD in both sexes and was significantly reduced by FGF23Ab. Increased SCD kidney damage marker kidney injury molecule 1 was rescued, but sclerotic glomeruli, increased macrophages, and lymphocytes were not rescued by short-term FGF23Ab. FGF23Ab significantly reduced increased phospho-fibroblast growth factor receptor 1, αKlotho, phosphorylated extracellular signal-regulated kinase, phosphorylated serum/glucocorticoid-regulated kinase 1, phosphorylated sodium-hydrogen exchanger regulatory factor-1, phosphorylated janus kinase 3, and phosphorylated transducer and activator of transcription-3 in SCD kidneys. The type II sodium Pi cotransporter (NPT2a) and sodium-dependent Pi transporter PiT-2 proteins were significantly reduced in SCD kidneys and were increased by FGF23Ab. We conclude that increased FGF23/FGF receptor 1/αKlotho signaling promotes Pi wasting in SCD by downregulating NPT2a and PIT2 via modulation of multiple signaling pathways that could be rescued by FGF23Ab.

Intracranial phosphaturic mesenchymal tumors. A case report and review of literature

Most osteomalacia-inducing tumors (OITs) are phosphaturic mesenchymal tumors (PMTs) that secrete fibroblast growth factor 23 (FGF23). These tumors usually occur in the bone and soft tissues, and intracranial OITs are rare. Therefore, intracranial OIT is difficult to diagnose and treat. This paper presents a case of intracranial OIT and shows a review of previous cases. A 45-year-old man underwent nasal cavity biopsy and treatment with active vitamin D₃ and neutral phosphate for hypophosphatemia. Amplification of FGF23 mRNA level within the tumor was detected. Subsequently, the surgical specimen was diagnosed with a PMT and was considered the cause of the patient's osteomalacia. The patient was referred to a neurosurgery department for the excision of the intracranial tumor extending to the nasal cavity. After tumor removal, the serum levels of FGF23 and phosphorus were normalized as compared to preoperative those. The patient remains disease-free, without additional treatment, approximately 10 years after surgery, with no tumor recurrence. As per the literature, intracranial OITs usually occur in patients aged 8-69 years. Bone and muscle pain are major complaints. Approximately 60% of the patients reported previously had symptoms because of intracranial tumors. In some cases, it took several years to diagnose OIT after the onset of the osteomalacia symptoms. Laboratory data in such cases show hypophosphatemia and elevated FGF23 levels. Because FGF23 levels are associated with the severity of osteomalacia symptoms, total tumor resection is recommended. PMT and hemangiopericytoma (HPC) are histologically similar, but on immunochemistry, PMT is negative for signal transducer and activator of transcription 6 (STAT6), whereas HPC is positive. FGF23 amplification is seen in PMTs but not in HPCs. Therefore, the analysis of FGF23 and STAT6 was helpful in distinguishing PMTs from HPCs. In cases of hypophosphatemia and osteomalacia without a history of metabolic, renal, or malabsorptive diseases, the possibility of oncogenic osteomalacia should be considered.

Pseudo-pheochromocytoma due to obstructive sleep apnea: a case report

SUMMARY

Obstructive sleep apnea (OSA) is a condition of intermittent nocturnal upper airway obstruction. OSA increases sympathetic drive which may result in clinical and biochemical features suggestive of pheochromocytoma. We present the case of a 65-year-old male with a 2.9-cm left adrenal incidentaloma on CT, hypertension, symptoms of headache, anxiety and diaphoresis, and persistently elevated 24-h urine norepinephrine (initially 818 nmol/day (89-470)) and normetanephrine (initially 11.2 µmol/day (0.6-2.7)). He was started on prazosin and underwent left adrenalectomy. Pathology revealed an adrenal corticoadenoma with no evidence of pheochromocytoma. Over the next 2 years, urine norepinephrine and normetanephrine remained significantly elevated with no MIBG avid disease. Years later, he was diagnosed with severe OSA and treated with continuous positive airway pressure. Urine testing done once OSA was well controlled revealed complete normalization of urine norepinephrine and normetanephrine with substantial symptom improvement. It was concluded that the patient never had a pheochromocytoma but rather an adrenal adenoma with biochemistry and symptoms suggestive of pheochromocytoma due to untreated severe OSA. Pseudo-pheochromocytoma is a rare presentation of OSA and should be considered on the differential of elevated urine catecholamines and metanephrines in the right clinical setting.

LEARNING POINTS

Obstructive sleep apnea (OSA) is a common condition among adults. OSA may rarely present as pseudo-pheochromocytoma with symptoms of pallor, palpitations, perspiration, headache, or anxiety. OSA should be considered on the differential of elevated urine catecholamines and metanephrines, especially in patients with negative metaiodobenzylguanidine (MIBG) scan results.

Hypophosphatemia in cancer patients

Dysregulation of phosphorus homeostasis resulting in hypophosphatemia is common in cancer patients and can result in serious complications and impact outcomes. Several factors, including critical illness, nutritional status, cancer type and therapy, influence the development of hypophosphatemia. Hypophosphatemia can develop as a result of phosphaturic mesenchymal tumors or as a paraneoplastic phenomenon. The clinical presentation for hypophosphatemia varies depending on the duration and severity of the hypophosphatemia and affects several organ systems. Among other serious effects, hypophosphatemia can impair tissue oxygenation and can cause hemolysis, leukocyte and platelet dysfunction, encephalopathy, seizures, arrhythmias, cardiomyopathy, rhabdomyolysis and coma. Multiple studies have demonstrated that hypophosphatemia is an adverse prognostic marker in inpatients with increased in-hospital stay, mortality and postoperative complications. The phosphate level is homeostatically regulated and maintained in a narrow range by three main hormones: parathyroid hormone, fibroblast growth factor 23 and 1,25-dihydroxyvitaminD₃. Together, these hormones regulate how the intestine, kidneys and bones traffic phosphorus. Several hematological malignancies and cancer therapies are associated with proximal tubular dysfunction (Fanconi syndrome), resulting in phosphaturia. Caution should be taken with parenteral administration of phosphate salts, because secondary complications can develop, principally due to hypocalcemia. The general approach to hypophosphatemia should target the underlying cause. Early recognition and prevention are essential and the approach to hypophosphatemia in the cancer patient, because of the nuances and complexity, should be multidisciplinary.

Unusual presentation of a five-month-old boy with NaPi2a homozygous mutation without hyperphosphaturia: Case report and review of the literature

Deletions of the NaPi2a gene and mutations in the SLC34A gene should be considered in patients with atypical presentation, without phosphaturia, with mild hypo to normal phosphatemia, and nephrocalcinosis.

Dietary Phosphorus as a Marker of Mineral Metabolism and Progression of Diabetic Kidney Disease

Phosphorus is an essential nutrient that is critically important in the control of cell and tissue function and body homeostasis. Phosphorus excess may result in severe adverse medical consequences. The most apparent is an impact on cardiovascular (CV) disease, mainly through the ability of phosphate to change the phenotype of vascular smooth muscle cells and its contribution to pathologic vascular, valvular and other soft tissue calcification. Chronic kidney disease (CKD) is the most prevalent chronic disease manifesting with the persistent derangement of phosphate homeostasis. Diabetes and resulting diabetic kidney disease (DKD) remain the leading causes of CKD and end-stage kidney disease (ESRD) worldwide. Mineral and bone disorders of CKD (CKD-MBD), profound derangement of mineral metabolism, develop in the course of the disease and adversely impact on bone health and the CV system. In this review we aimed to discuss the data concerning CKD-MBD in patients with diabetes and to analyze the possible link between hyperphosphatemia, certain biomarkers of CKD-MBD and high dietary phosphate intake on prognosis in patients with diabetes and DKD. We also attempted to clarify if hyperphosphatemia and high phosphorus intake may impact the onset and progression of DKD. Careful analysis of the available literature brings us to the conclusion that, as for today, no clear recommendations based on the firm clinical data can be provided in terms of phosphorus intake aiming to prevent the incidence or progression of diabetic kidney disease.

Assessment of Inorganic Phosphate Intake by the Measurement of the Phosphate/Urea Nitrogen Ratio in Urine

In chronic kidney disease (CKD) patients, it would be desirable to reduce the intake of inorganic phosphate (P) rather than limit the intake of P contained in proteins. Urinary excretion of P should reflect intestinal absorption of P(inorganic plus protein-derived). The aim of the present study is to determine whether the ratio of urinary P to urinary urea nitrogen (P/UUN ratio) helps identify patients with a high intake of inorganic P.A cross-sectional study was performed in 71 patients affected by metabolic syndrome with CKD (stages 2–3) with normal serum P concentration. A 3-day dietary survey was performed to estimate the average daily amount and the source of P ingested. The daily intake of P was 1086.5 ± 361.3 mg/day; 64% contained in animal proteins, 22% in vegetable proteins, and 14% as inorganic P. The total amount of P ingested did not correlate with daily phosphaturia, but it did correlate with the P/UUN ratio (p < 0.018). Patients with the highest tertile of the P/UUN ratio >71.1 mg/g presented more abundant inorganic P intake (p < 0.038).The P/UUN ratio is suggested to be a marker of inorganic P intake. This finding might be useful in clinical practices to identify the source of dietary P and to make personalized dietary recommendations directed to reduce inorganic P intake.

Urinary Fractional Excretion of Phosphorus in Dogs with Spontaneous Chronic Kidney Disease

The increase of urinary fractional excretion of phosphorus (uFEP) may indicate phosphorus retention before the onset of hyperphosphatemia in the early stages of chronic kidney disease (CKD). The hypothesis of this study is whether uFEP may increase during the early stage of CKD as a compensatory mechanism to prevent hyperphosphatemia as well as whether hyperphosphatemia in the late stages is associated with increase or decrease in uFEP in dogs with naturally occurring CKD; therefore, the aim of this study was to determine the uFEP in CKD dogs with different stages. Forty-nine CKD dogs were included, and they were divided into stage 1 (serum creatinine < 1.4 mg/dL), stage 2 (serum creatinine 1.5 to 2.0 mg/dL), stage 3 (serum creatinine 2.1 to 5.0 mg/dL) and stage 4 (serum creatinine > 5.0 mg/dL), according to the IRIS staging criteria. The stage 3 was subdivided into stage 3-A (serum creatinine 2.1 to 3.5 mg/dL) and stage 3-B (serum creatinine 3.6 to 5.0 mg/dL). The control group comprised 10 dogs, and uFEP ≤ 40% was considered as normal. A progressive increase in uFEP along the progression of CKD was found. However, similar results of uFEP levels were observed in late CKD, since there were no differences between stages 3 (A, B) and 4. Interestingly, some CKD dogs with stage 4 showed normal or reduced uFEP, besides hyperphosphatemia; conversely, some dogs in early CKD had increased uFEP values and normophosphatemia. Our findings suggest that uFEP may act as a compensatory mechanism to avoid the onset of hyperphosphatemia in early CKD, but not in later stages. uFEP assessment may be considered as an additional tool for the diagnostic and monitoring of phosphate disorders in dogs with CKD, since it may help to identify disturbances of phosphorus balance. More studies are needed to elucidate the role of uFEP in phosphorus homeostasis in dogs with CKD.

Differential regulation of renal Klotho and FGFR1 in normal and uremic rats

In renal failure, hyperphosphatemia occurs despite a marked elevation in serum fibroblast growth factor (FGF)-23. Abnormal regulation of the FGFR1-Klotho receptor complex may cause a resistance to the phosphaturic action of FGF23. The purpose of the present study was to investigate the regulation of renal Klotho and FGF receptor (FEFR)-1 in healthy and uremic rats induced by 5/6 nephrectomy. In normal rats, the infusion of rat recombinant FGF23 enhanced phosphaturia and increased renal FGFR1 expression; however, Klotho expression was reduced. Uremic rats on a high-phosphate (HP) diet presented hyperphosphatemia with marked elevation of FGF23 and an increased fractional excretion of phosphate (P) that was associated with a marked reduction of Klotho expression and an increase in FGFR1. After neutralization of FGF23 by anti-FGF23 administration, phosphaturia was still abundant, Klotho expression remained low, and the FGFR1 level was reduced. These results suggest that the expression of renal Klotho is modulated by phosphaturia, whereas the FGFR1 expression is regulated by FGF23. Calcitriol (CTR) administration prevented a decrease in renal Klotho expression. In HEK293 cells HP produced nuclear translocation of β-catenin, together with a reduction in Klotho. Wnt/β-catenin inhibition with Dkk-1 prevented the P-induced down-regulation of Klotho. The addition of CTR to HP medium was able to recover Klotho expression. In summary, high FGF23 levels increase FGFR1, whereas phosphaturia decreases Klotho expression through the activation of Wnt/β-catenin pathway.-Muñoz-Castañeda, J. R., Herencia, C., Pendón-Ruiz de Mier, M. V., Rodriguez-Ortiz, M. E., Diaz-Tocados, J. M., Vergara, N., Martínez-Moreno, J. M., Salmerón, M. D., Richards, W. G., Felsenfeld, A., Kuro-O, M., Almadén, Y., Rodríguez, M. Differential regulation of renal Klotho and FGFR1 in normal and uremic rats.

Postprandial adjustments in renal phosphate excretion do not involve a gut-derived phosphaturic factor

NEW FINDINGS

What is the central question of this study? Does a previously hypothesized signalling mechanism, believed to detect postprandial increases in intestinal phosphate and that can stimulate the kidneys to rapidly excrete phosphate, operate under physiological conditions? What is the main finding and its importance? Contrary to earlier reports, rapid signalling between the small intestine and kidney mediated by a gut-derived phosphaturic factor in response to a physiological intestinal phosphate load is not supported by the present findings; moreover, hyperphosphataemia and increased parathyroid hormone concentrations are likely to be the underlying factors responsible for the phosphaturia following a supraphysiological intestinal phosphate load. To date, the role of the small intestine in the regulation of postprandial phosphate homeostasis has remained unclear and controversial. Previous studies have proposed the presence of a gut-derived phosphaturic factor that acts independently of changes in plasma phosphate concentration or parathyroid hormone (PTH) concentration; however, these early studies used duodenal luminal phosphate concentrations in the molar range, and therefore, the physiological relevance of this is uncertain. In the present study, we used both in vivo and in vitro approaches to investigate the presence of this putative 'intestinal phosphatonin'. Instillation of 1.3 m phosphate into the duodenum rapidly induced phosphaturia, but in contrast to previous reports, this was associated with significant hyperphosphataemia and elevated PTH concentration; however, there was not the expected decrease in abundance of the renal sodium-phosphate cotransporter NaPi-IIa. Instillation of a physiological (10 mm) phosphate load had no effect on plasma phosphate concentration, PTH concentration or phosphate excretion. Moreover, phosphate uptake by opossum kidney cells was unaffected after incubation with serosal fluid collected from intestinal segments perfused with different concentrations of phosphate. Taken together, these findings do not support the concept of a gut-derived phosphaturic factor that can mediate rapid signalling between the gut and kidney, leading to increased urinary phosphate excretion, as part of normal phosphate homeostasis.

From epistaxis to bone pain-report of two cases illustrating the clinicopathological spectrum of phosphaturic mesenchymal tumour with fibroblast growth factor receptor 1 immunohistochemical and cytogenetic analyses

AIMS

Phosphaturic mesenchymal tumour (PMT) is a rare, recently described neoplastic entity. It is characterized by distinct histological features, which often occur together with oncogenic osteomalacia. Recently, a novel FN1-FGFR1 gene fusion has been described in a subset of PMTs. The aim of this study is to characterise the clinicopathological features of two PMTs, with FGFR1 immunohistochemical and cytogenetic analyses.

METHODS AND RESULTS

We present two contrasting cases of PMT, one occurring in the sinonasal region, and the other occurring in bone (proximal femur). In the former, local effects, including epistaxis and anosmia, dominated the clinical presentation, whereas the latter case presented with refractory bone pain, muscle weakness, and occult osteomalacia, the cause of which was only identified after 2 years. Both tumours showed characteristic histological features of PMT, including a monomorphic proliferation of round to ovoid cells, osteoclast-like multinucleated giant cells, and areas of 'smudgy' basophilic calcifications. Chromogenic in-situ hybridization showed fibroblast growth factor FGF-23 expression by the sinonasal tumour. By using immunohistochemistry, we also demonstrated, for the first time, FGF receptor 1 (FGFR1) protein overexpression in this tumour, for which FN1-FGFR1 gene fusion was not detected by fluorescence in-situ hybridization.

CONCLUSIONS

Our findings indicate that up-regulation of FGFR1 in phosphaturic mesenchymal tumours can occur via mechanisms other than FN1-FGFR1 fusion, raising the possibility of FGFR1 overexpression being a potential common pathway with pathophysiological and therapeutic implications.

Case report: proximal tubule impairment following volatile anesthetic exposure

The safety of contemporary volatile anesthetic agents with respect to kidney function is well established, and growing evidence suggests that volatile anesthetics even protect against ischemic nephropathy. However, studies examining effects of volatile anesthetics on kidney function frequently demonstrate transient proteinuria and glycosuria following exposure to these agents, although the cause of these findings has not been thoroughly examined. We describe the case of a patient who underwent a neurosurgical procedure, then experienced glycosuria without hyperglycemia that resolved within days. Following a second neurosurgical procedure, the patient again developed glycosuria, now associated with ketonuria. Further examination demonstrated nonalbuminuric proteinuria in conjunction with urinary wasting of phosphate and potassium, indicative of proximal tubule impairment. We suggest that transient proximal tubule impairment may play a role in the proteinuria and glycosuria described following volatile anesthetic exposure and discuss the relationship between these observations and the ability of these agents to protect against ischemic nephropathy.

Phosphaturic mesenchymal tumour mixed connective tissue variant: report of three cases with unusual histological findings

Phosphaturic mesenchymal tumour mixed connective tissue variant (PMTMCT) is a rare tumour occurring in bone and soft tissue that usually behaves in a benign manner. Elaboration of biologically active substances by this tumour gives rise to a paraneoplastic syndrome known as oncogenic osteomalacia, manifesting clinically as bone pain, generalized weakness and pathological fractures. Recognition of PMTMCT and its associated syndrome is important, as resection of the tumour in most instances results in prompt resolution of symptoms. Previously reported cases of this tumour have emphasized the consistent presence of certain histological features that are considered prerequisite for making the diagnosis of PMTMCT. We describe three cases of PMTMCT, of which two first presented with progressive symptoms of osteomalacia and one remained clinically silent aside from the symptom of a palpable lump. Our cases highlight the wide-ranging histological patterns displayed by these tumours, and draw attention to certain microscopic findings that until now have been given little if any mention. Tentacular growth pattern and satellite nodules appear to be common findings in PMTMCTs, and can make complete surgical excision of these tumours challenging. The ability of this otherwise histologically benign tumour to permeate vascular spaces has to our knowledge never been described previously. One tumour lacked the characteristic calcifying matrix of PMTMCT, suggesting that in some tumours this defining feature may be focal if not entirely absent. PMTMCT shares features with and can resemble a variety of bone and soft tissue neoplasms, requiring the surgical pathologist to be familiar with this entity.

Changes in fibroblast growth factor 23 levels in normophosphatemic patients with chronic kidney disease stage 3 treated with lanthanum carbonate: results of the PREFECT study, a phase 2a, double blind, randomized, placebo-controlled trial

BACKGROUND

High levels of circulating fibroblast growth factor 23 (FGF23) are associated with chronic kidney disease (CKD) progression and high mortality. In the Phosphate Reduction Evaluation of FGF23 in Early CKD Treatment (PREFECT) study, we assessed the effect of reducing intestinal phosphate absorption using lanthanum carbonate on FGF23 levels in normophosphatemic patients with CKD stage 3.

METHODS

Thirty-five individuals were randomized to lanthanum carbonate 3000 mg/day (n=23) or placebo (n=12) for 12 weeks. Levels of intact FGF23 (iFGF23), C-terminal FGF23, serum and urinary phosphate and calcium, intact parathyroid hormone and 1,25-dihydroxyvitamin D were assessed.

RESULTS

The median age was 65 years in the lanthanum group and 73 years in the placebo group; 58.8% and 41.7% were men, respectively. No significant difference was seen in mean iFGF23 between groups at week 12. There was, however, a transient reduction from baseline in iFGF23 in the lanthanum group at week 1, from 70.5 pg/ml to 51.9 pg/ml, which was not seen in the placebo group; this between-group difference in percentage change from baseline was significant in post hoc analyses (p=0.0102). Urinary phosphate decreased after 1 week of lanthanum treatment and remained low at week 12.

CONCLUSIONS

Reducing intestinal phosphate absorption with lanthanum carbonate did not lead to sustained reductions in iFGF23 in patients with CKD stage 3, although phosphaturia decreased. This suggests that factors other than phosphate burden may be responsible for driving increases in circulating FGF23 in patients with CKD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01128179, 20 May 2010.

Effects of a 250-mL enema containing sodium phosphate on electrolyte concentrations in healthy volunteers: An open-label, randomized, controlled, two-period, crossover clinical trial

BACKGROUND

Enemas are used by individuals with constipation and are often required before certain medical diagnostic procedures and surgical interventions. However, abnormalities in serum electrolyte concentrations have been associated with enema use.

OBJECTIVE

The aim of this study was to determine the changes in serum electrolyte concentrations (phosphorus, calcium, sodium, and potassium) and urinary phosphorus elimination after the administration of a sodium phosphate enema.

METHODS

Healthy volunteers aged 35 to 70 years were eligible for this open-label, randomized, controlled, 2-period, crossover clinical trial at the Clinical Research Unit of the University Hospital of Navarra, Pamplona, Spain. The study comprised 2 one-day periods separated by a 7-day washout. All subjects were randomly assigned in a 1:1 ratio to 1 of 2 study sequences: (1) a single dose of Enema Casen® 250 mL in the first period followed by no treatment (control) in the second period, or (2) no treatment in the first period followed by a single dose of the study drug in the second period. The sequence of treatment was assigned using a randomization table that was prepared before the beginning of the study. Serum concentrations of phosphorus, sodium, potassium, and calcium were measured in both periods. Urinary phosphorus elimination was measured for 12 hours after enema administration (Ae0-12) in a subset of the subjects in the second period. Adverse events (AEs) were monitored by the investigators throughout the study. Normal ranges for the electrolytes were as follows: phosphorus, 2.5 to 5 mg/dL; calcium, 8.5 to 10.5 mg/dL; sodium, 135 to 145 mEq/L; and potassium, 3.5 to 5 mEq/L.

RESULTS

Twenty-four subjects (12 men, 12 women; mean [SD] age, 47.8 [9.6] years [range, 36-68 years]) participated in the study. All of the subjects were white and none were smokers. Twelve hours after enema administration, mean serum phosphorus and sodium concentrations increased by a mean of 1.18 mg/dL and 1.32 mEq/L, respectively (both, P < 0.001). Mean serum phosphorus concentrations were above the upper limit of normal (5 mg/dL) at 30 and 60 minutes after enema administration. In all subjects the values returned to normal within 4 hours after enema administration; a meal was provided after a 3-hour fast. Four subjects (16.7%) had ≥1 serum phosphorus concentration measurement ≥7 mg/dL, a value that is considered serious hyperphosphatemia. A statistically significant correlation was found between phosphorus Cmax and enema retention time (r (2) = 0.452; P < 0.001). No abnormal serum concentrations were obtained for the other electrolytes measured. Phosphorus Ae0-12 was increased after enema administration by 86% (P < 0.001). No serious AEs were observed, although 13 AEs were reported in 9 subjects. None of the changes in serum electrolyte concentrations were associated with clinical symptoms.

CONCLUSIONS

Administration of an enema containing 250 mL of sodium phosphate was associated with serum phosphorus concentrations of ≥7 mg/dL in 16.7% of the healthy subjects who participated in the study; however, none of those subjects experienced hypocalcemia. Enema retention time was significantly correlated with the degree of phosphatemia.

Treatment of Hypophosphatemic Rickets with Phosphate and Active Vitamin D in Japan: A Questionnaire-based Survey

Hereditary hypophosphatemic rickets represented by X-linked hypophosphatemic rickets (XLH) is a rare disorder characterized by hypophosphatemia, elevated alkaline phosphatase (ALP) and undermineralization of bone. Active vitamin D and phosphate are administered to correct hypophosphatemia and elevation of ALP. Overtreatment with phosphate leads to secondary hyperparathyroidism, and a large dose of active vitamin D has a risk of hypercalciuria. To understand the situation concerning treatment of patients with hereditary hypophosphatemic rickets in Japan, we conducted a questionnaire survey of pediatric endocrinologists. Answers were obtained from 53 out of 68 hospitals where the pediatric endocrinologists worked. One hundred and thirty-five patients were treated in 28 hospitals during November 2009 and May 2010; 126 patients suffered from hereditary hypophosphatemic rickets, and 9 had hypophosphatemia caused by other miscellaneous reasons. The distribution of patient age was as follows: 27 (21%) were between 6 mo and 6 yr of age, 39 (31%) were between 6 and 12 yr of age, and 60 (48%) were more than 12 yr of age. Active vitamin D was given to 123 patients, and phosphate was given to 106 patients. As for the dose of phosphorus, 37.2–58.1 mg/kg/d was given divided into 2 to 6 aliquots. There were various control targets of treatment, including serum phosphate, serum ALP, rachitic change, urinary Ca/Cr, parathyroid hormone and growth. It is very important to avoid side effects of these treatments. No evidence is available about the optimal dose of phosphate or number of administrations in the treatment of patients with hypophosphatemic rickets. Although there is a recommendation for clinical management of patients with hypophosphatemic rickets, we should set a clinical guideline for it in Japan.

Klotho and kidney disease

Klotho is a single-pass transmembrane protein that exerts its biological functions through multiple modes. Membrane-bound Klotho acts as coreceptor for the major phosphatonin fibroblast growth factor-23 (FGF23), while soluble Klotho functions as an endocrine substance. In addition to in the distal nephron where it is abundantly expressed, Klotho is present in the proximal tubule lumen where it inhibits renal Pi excretion by modulating Na-coupled Pi transporters via enzymatic glycan modification of the transporter proteins - an effect completely independent of its role as the FGF23 coreceptor. Acute kidney injury (AKI) and chronic kidney disease (CKD) are states of systemic Klotho deficiency, making Klotho a very sensitive biomarker of impaired renal function. In addition to its role as a marker, Klotho also plays pathogenic roles in renal disease. Klotho deficiency exacerbates decreases in, while Klotho repletion or excess preserves, glomerular filtration rate in both AKI and CKD. Soft tissue calcification, and especially vascular calcification, is a dire complication in CKD, associated with high mortality. Klotho protects against soft tissue calcification via at least 3 mechanisms: phosphaturia, preservation of renal function and a direct effect on vascular smooth muscle cells by inhibiting phosphate uptake and dedifferentiation. In summary, Klotho is a critical molecule in a wide variety of renal diseases and bears great potential as a diagnostic and prognostic biomarker as well as for therapeutic replacement therapy.

Molecular bases of diseases characterized by hypophosphatemia and phosphaturia: new understanding

Serum phosphate levels are regulated in both calcium-dependent and -independent fashions. Active vitamin D increases while PTH decreases serum phosphate levels in association with the elevation of serum calcium. On the other hand, a calcium-independent phosphaturic factor, historically called phosphatonin is believed to exert a physiological function based on findings in hereditary and tumor-induced diseases characterized by hypophosphatemia with normocalcemia. Among them, autosomal dominant hypophosphatemic rickets (ADHR) has contributed greatly to its elucidation because the gene responsible for ADHR encodes fibroblast growth factor 23 (FGF23) that has been found to have a phosphaturic effect. In addition, FGF23 has been proved to be involved in most cases of oncogenic osteomalacia and X-linked hypophosphatemic rickets that are also characterized by hypophosphatemia and normocalcemia. Moreover, familial tumoral calcinosis, which represents the metabolic mirror image of hypophosphatemic conditions, is caused by a loss-of-function mutation in the FGF23 gene in some patients. Very recently, hereditary hypophosphatemic rickets with hypercalciuria has been found to be caused by mutations in the SLC34A1 gene which encodes a type of sodium phosphate cotransporter. These findings may provide new strategies for treating patients with abnormal phosphate metabolism.

Sarcocystis infection in wild reindeer (Rangifer tarandus) from Hardangervidda in southern Norway: with a description of the cysts of Sarcocystis hardangeri n. sp

Fresh preparations of micro-isolated sarcosysts from skeletal muscle of 5 wild reindeer were examined by light microscopy. Slender, spindelshaped cysts measuring 821 × 60 µm, and having short knob-like cyst wall protrusions were found in all animals. In 1 animal cysts different in structure from the cysts of the 4 previously known Sarcocystis spp. of reindeer were found, These cysts are considered to be cysts of a new Sarcocystis sp. of reindeer, for which the name Sarcocystis hardangeri has been proposed.

S. hardangeri n. sp. had macroscopic, ovoid to cylindrical cysts measuring 1667 (900–2570) × 819 (450–1575) µm. The cysts were surrounded by a 8–10 µm thick layer of fibrillar material. After removal of this layer, relatively few and irregularly spaced, slanting protrusions became visible. The 20–30 µm long protrusions were tongue-like, and were lying close to the surface of the cyst.

Cysts of S. grueneri, S. rangiferi and S. tarandi were not demonstrated in the 5 wild reindeer examined.