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X-linked hypophosphataemia (XLH) rickets is a rare disease frequently misdiagnosed and mismanaged. Despite having clinical guidelines that offers some therapeutic recommendations based on the clinical experience of experts, physicians still have questions about some important aspects of the diagnosis and treatment of XLH, such as when the disease should be suspected, who should be in charge of the diagnosis, what should be done once the disease is diagnosed, or what therapeutic options are currently available. The objective of this paper is to answer some of the more frequent questions related to the management of patients with XLH by a group of experts participating in a scientific conference on XLH held in Madrid.

Background Cardiovascular calcification (CVC) is a major concern in hemodialysis (HD) and the loss of endogenous modulators of calcification seems involved in the process. Phytate is an endogenous crystallization inhibitor and its low molecular mass and high water solubility make it potentially dialyzable. SNF472 (the hexasodium salt of phytate) is being developed for the treatment of calciphylaxis and CVC in HD patients. We aimed to verify if phytate is lost during dialysis, and evaluate SNF472's behaviour during dialysis. Methods Dialyzability was assessed in vitro using online-hemodiafiltration and high-flux HD systems in blood and saline. SNF472 was infused for 20 min and quantified at different time points. Results Phytate completely dialyzed in 1 h at low concentrations (10 mg/l) but not when added at 30 or 66.67 mg/l SNF472. In bypass conditions, calcium was slightly chelated during SNF472 infusion but when the system was switched to dialysis mode the calcium in the bath compensated this chelation. Conclusion Phytate dialyses with a low clearance. The administration of SNF472 as an exogenous source of phytate allows to attain supra-physiological levels required for its potential therapeutic properties. As SNF472 is infused during the whole dialysis session, the low clearance would not affect the drug's systemic exposure., This study has been supported by REDINREN RD012/0021 and RETOS COLABORACION RTC201424601 ISCIII (Ministerio de Economia y Competitividad. Government of Spain) grants.

In the original article, third author name has been published incorrectly.

The aim of the present study was to evaluate the effect of hemodialysis and renal failure on serum bone markers. Serum total alkaline phosphatase (TAP), procollagen type I aminoterminal propeptide (PINP), and beta-carboxyterminal telopeptide of type I collagen (beta-CTX), as well as intact parathyroid hormone (iPTH), creatinine, and total protein were measured in 14 patients with endstage renal disease (ESRD) before and at 1, 2, and 4 h during a hemodialysis session, and at the same sampling interval in 6 renal transplant recipients. The results were compared to those obtained in 20 healthy adults. All patients showed increased baseline mean values of PINP, beta-CTX, and iPTH. Beta-CTX differed significantly between hemodialysis patients and renal transplant recipients. TAP and beta-CTX were the only markers which correlated with iPTH ( P << 0.05) and creatinine values ( P << 0.001), respectively. Renal transplant recipients did not show significant variations in the evolution of mean values of bone markers throughout the study, whereas, during the dialysis period, all the bone markers analyzed in the study showed a significant change. The change differed depending on the marker considered: beta-CTX showed a significant decrease at the end of the session, TAP increased at this time and, although PINP showed an initial increase during hemodialysis, no significant changes were observed at the end of the session. We conclude that bone markers are significantly influenced by hemodialysis, especially serum TAP and beta-CTX. ESRD is associated with an increase in these bone markers, in some cases related to iPTH values and in others to glomerular function. These findings should be taken into account when evaluating bone markers in these patients.

Methods We analyzed all PRA-negative patients who received a first kidney transplant from an HLA-identical living donor. The patients received no antibody induction. An intraoperative bolus of 500 mg of methylprednisolone was administered. Then, steroid therapy was withdrawn within one week. Tacrolimus and mycophenolate treatment were started 3 days before transplantation with tacrolimus target levels of 4 to 8 ng/mL. In the absence of rejection, tacrolimus was withdrawn between 3 and 12 months post-transplant to reach mycophenolate mofetil monotherapy of 2 g/day or equivalent. Results Six patients were treated with the above protocol. At last follow-up, graft and patient survival were 100%. MDRD glomerular filtration rates were 54, 60, and 62 mL/min at 3 months, 12 months and last follow-up, respectively. None of the patients developed PRA post-transplant. One episode of acute rejection Banff IA occurred 9 years after transplantation due to non-adherence with good outcome after treatment. The mean number of concomitant drugs given with mycophenolate was 2.6. Four patients needed antihypertensive drugs. Conclusion Steroid-free de novo treatment and calcineurin-inhibitor weaning with mycophenolate monotherapy is feasible in first HLA-identical kidney transplantation from a living sibling. Although recipients of a first HLA-identical living-donor kidney transplant seem to need less immunosuppression, there are no guideline recommendations for these patients, and few prospective trials are available.

Double-phase parathyroid MIBI (99mTc-sestamibi) was performed in 27 patients with secondary hyperparathyroidism (SPT). Focal areas of increased uptake were scored for intensity on a three-point scale. All patients underwent subtotal parathyroidectomy (SPTx), and a total of 78 glands were removed at operation. Blood was obtained from the jugular vein before and after SPTx to measure the parathyroid hormone (PTH) levels. The volume and weight of the glands were calculated. The tissue was divided, with one aliquot being used for cell cycle analysis. The nuclei were acquired by flow cytometry and analyzed using CELLEIT software. Cell viability was assessed by flow cytometry and analyzed with LYSIS II software. Positive MIBI uptake was observed in 88.8% of patients. Focal MIBI uptake of one, two, or three glands was observed in 6, 11, and 8 patients, respectively. All patients experienced an 86% decrease in PTH blood level after SPTx compared to that before excision. A correlation was found between the volume of glands and the blood levels of intact PTH (iPTH) (r= 0.5, p < 0.05). A positive correlation was observed between MIBI uptake and the iPTH levels before SPTx (p < 0.01) and between the uptake of MIBI in the parathyroid glands and the cell cycle phases; low-grade uptake correlated with the G0 phase and higher uptake with G2+S phase (r= 7, p < 0.01). No correlation was observed between MIBI uptake and the weight of the glands. MIBI scintigraphy accurately reflects the functional status of the hyperplastic parathyroid glands: Higher uptake grades correlated with the active growth phase. MIBI uptake does not reveal parathyroid enlargement; rather, it identifies the presence of hyperfunctioning autonomous glands. SPTx and total parathyroidectomy with autografting (TPTx+A) are the most widely accepted surgical approaches for patients with SPT. Reoperation for recurrence is necessary in 6% to 15% of cases. MIBI is now considered to be the radionuclide of reference for parathyroid gland scanning, although it is widely accepted that it produces poor results when trying to detect hyperplastic glands.