Sustained hypophosphatemia after denosumab in a patient on hemodialysis.

An 81-year-old Caucasian man who had commenced thrice weekly hemodialysis (HD) three months earlier, presented with a hip fracture, two vertebral fractures and a bone mineral density T-score of -3.6. He had received weekly iron sucrose infusions for 6 weeks and alphacalcidol on dialysis days. Although he suffered from coeliac disease and cirrhosis, he was fully ambulatory and well-nourished. He was normocalcaemic with a marginally low plasma phosphate and the PTH was 11.8 pmol/L (<2-times the upper range of the assay). In view of his severe osteoporosis, it was decided to treat him with denosumab (dmab). Laboratory assessment 2 weeks post dmab showed severe hypophosphatemia and hypocalcemia; phosphate 0.11 mmol/L and ionized calcium 0.83 mmol/L, and he was admitted for intravenous phosphate infusion. Three months later he remained on a phosphate supplement. The case illustrates that, in addition to the risks of hypocalcemia in patients with kidney failure and high bone turnover, kidney failure patients without evidence of high bone turnover, can also be at risk of hypocalcemia and severe hypophosphatemia requiring acute hospitalization and phosphate infusion. The potential role of compromised phosphate absorption versus increased deposition will be discussed. We recommend a cautious approach to dmab therapy in patients on dialysis, with evaluation of bone turnover and serum phosphate levels prior to initiation of treatment.

Refeeding syndrome and psychopharmacological interventions in children and adolescents with Anorexia Nervosa: a focus on olanzapine-related modifications of electrolyte balance.

This study aims to investigate the potential correlation between the use of olanzapine, a psychopharmacological intervention commonly prescribed in Anorexia Nervosa treatment, and the occurrence of Refeeding Syndrome. Despite the acknowledged nutritional and biochemical impacts of olanzapine, the literature lacks information regarding its specific association with Refeeding Syndrome onset in individuals with Anorexia Nervosa. This is a naturalistic, retrospective, observational study, reporting the occurrence of Refeeding Syndrome in children and adolescents with Anorexia Nervosa, treated or untreated with olanzapine. Dosages and serum levels of olanzapine were assessed for potential associations with the occurrence of Refeeding Syndrome and specific variations in Refeeding Syndrome-related electrolytes. Overall, 113 patients were enrolled, including 46 (41%) who developed a Refeeding Syndrome. Mild (87%), moderate (6.5%), and severe (6.5%) Refeeding Syndrome was described, at a current average intake of 1378 ± 289 kcal/day (39 ± 7.7 kcal/kg/die), frequently associated with nasogastric tube (39%) or parenteral (2.2%) nutrition. Individuals receiving olanzapine experienced a more positive phosphorus balance than those who did not (F(1,110) = 4.835, p = 0.030), but no difference in the occurrence of Refeeding Syndrome was documented. The mean prescribed doses and serum concentrations of olanzapine were comparable between Refeeding Syndrome and no-Refeeding Syndrome patients.    Conclusion: The present paper describes the occurrence of Refeeding Syndrome and its association with olanzapine prescriptions in children and adolescents with Anorexia Nervosa. Olanzapine was associated with a more positive phosphorus balance, but not with a different occurrence of Refeeding Syndrome. Further, longitudinal studies are required. What is Known: • Refeeding Syndrome (RS) is a critical complication during refeeding in malnourished patients, marked by electrolyte (phosphorus, magnesium, potassium) imbalances. • Olanzapine, an atypical antipsychotic with nutritional and biochemical impacts, is used in Anorexia Nervosa (AN) treatment, however data concerning its association with RS are lacking. What is New: • The study observed RS in 46/113 (41%) young patients with AN. • Olanzapine-treated individuals showed a higher improvement in serum phosphate levels than untreated ones, although no impact on the occurrence of Refeeding Syndrome was observed.

Renal histology of Fanconi syndrome associated with adefovir dipivoxil: A case report.

A sporadic occurrence of Fanconi syndrome associated with adefovir dipivoxil (ADV) has been reported, particularly when confirmed by renal biopsy. This study presents the case of a 53-year-old man who had been taking ADV 10 mg daily for 10 years to treat chronic hepatitis B (CHB) and subsequently developed Fanconi syndrome. The clinical manifestations included hypophosphatemic osteomalacia, glucosuria, renal tubular acidosis, low-molecular-weight proteinuria, and renal insufficiency. Renal biopsy revealed significant injury to proximal tubular epithelial cells, including vacuolar degeneration and regeneration of tubular epithelial cells. The ultrastructural pathology indicated severe morphological abnormalities of mitochondria, such as densely packed and enlarged mitochondria, with loss, blunting, and disordered arrangement of cristae. Following discontinuation of ADV and supplementation with oral phosphate, hypophosphatemia, glucosuria, and proteinuria were resolved. These findings support the previous hypothesis that ADV-induced nephrotoxicity may involve mitochondrial injury.

[Hypophosphatemia associated with use of intravenous ferric carboxymaltose]. / Hipofosfatemia asociada a uso de carboximaltosa férrica endovenosa.

Introduction: Introduction: ferric carboxymaltose (CF) is an intravenous preparation that helps the rapid correction of anemia with a lower risk of adverse reactions. However, an association has been found between the administration of CF and the development of hypophosphatemia. Case report: we present the clinical case of a 57-year-old patient with a history of iron de-ficiency anemia who, after receiving treatment with CF (Ferinjet®) chronically, develops a clinical of severe muscle weakness. Laboratory tests showed hypophosphatemia, normocalcemia, normal vitamin D level (after correction) and increased renal excretion of phosphorus. After study, the diagnosis of chronic hypophosphatemia secondary to the use of CF is reached. Discussion: CF can cause an increase in FGF-23 which acts at the renal level inducing phosphaturia, which can generate severe hypophosphatemia. This case demonstrates the importance of recognizing and treating this clinical entity in time.

Introducción: Introducción: la carboximaltosa férrica (CF) es una preparación intravenosa que ayuda a la corrección rápida de anemia con menor riesgo de reacciones adversas. Sin embargo, se ha encontrado asociación entre la administración de la CF y el desarrollo de hipofosfatemia. Caso clínico: presentamos el caso clínico de una paciente de 57 años con anemia ferropénica que tras recibir tratamiento con CF (Ferinjet®) de forma crónica, desarrolla un cuadro clínico de debilidad muscular severa. En la analítica se aprecia hipofosfatemia, normocalcemia, nivel de vitamina D normal (tras corrección) y aumento de excreción renal de fósforo. Tras estudio se llega al diagnóstico de hipofosfatemia crónica secundaria al uso de la CF. Discusión: la CF puede provocar un aumento de FGF-23 el cual actúa a nivel renal induciendo fosfaturia, pudiendo generar hipofosfatemia grave. Este caso demuestra la importancia de reconocer y tratar esta entidad clínica a tiempo.

Incidence of Hypophosphatemia After Intravenous Administration of Iron: A Matching-Adjusted Indirect Comparison of Data from Japanese Randomized Controlled Trials.

INTRODUCTION: Intravenous (IV) administration of iron is considered a safe and efficacious treatment for iron deficiency anemia (IDA), recommended in patients requiring rapid replenishment of iron, or intolerant or unresponsive to oral administration of iron. Recent randomized controlled trials (RCTs) have shown high incidence of hypophosphatemia after administration of two IV iron preparations: saccharated ferric oxide (SFO) and ferric carboxymaltose (FCM). The present study aimed to conduct matching-adjusted indirect comparison (MAIC) of hypophosphatemia incidence with these iron formulations and ferric derisomaltose (FDI) based on data from head-to-head RCTs conducted in Japan. METHODS: A MAIC of hypophosphatemia incidence was conducted on the basis of data from two head-to-head RCTs. The relative odds of hypophosphatemia with FDI versus SFO were obtained from patient-level data from a recent RCT and adjusted for cumulative iron dose, while parametric models of serum phosphate levels from a separate RCT were used to estimate the relative odds of hypophosphatemia with FCM with SFO. An anchored MAIC was then conducted comparing FDI with FCM. RESULTS: The adjusted odds of experiencing hypophosphatemia were significantly lower with FDI than SFO [odds ratio (OR) of 0.02; 95% confidence interval (CI) 0.01-0.05]. The parametric models of serum phosphate from the RCT comparing FCM with SFO provided an estimated OR of 1.17 for the incidence of hypophosphatemia with FCM versus SFO. Combining the two estimates in the MAIC showed that the odds of experiencing hypophosphatemia would be 52.5 (95% CI 27.7-99.4) times higher with FCM than FDI in patients with IDA associated with heavy menstrual bleeding in Japan. CONCLUSIONS: Direct comparison of patient-level data and a MAIC from two RCTs in Japanese patients with heavy menstrual bleeding indicated that hypophosphatemia is less frequent in patients treated with FDI than those with FCM or SFO. Results are in agreement with RCTs comparing FDI and FCM in patients with various etiologies conducted in the USA and Europe.

What is wrong in doing good?

Hypophosphataemia is a common side-effect in patients with iron deficiency anaemia treated with ferric carboxymaltose, which is not a class effect of all intravenous (IV) iron formulations. The report by Chu et al. shows that moderate and severe hypophosphataemia is common and can even require IV supplementation of phosphate with unknown long-term consequences. Commentary on: Chu et al. Incidence and predictors of hypophosphataemia after ferric carboxymaltose use-a 3-year experience from a single institution in Singapore. Br J Haematol 2023;202:1199-1204.

Efficacy and Safety of Burosumab in X-linked Hypophosphatemia.

CONTEXT: Burosumab is approved for the treatment of X-linked hypophosphatemia (XLH). OBJECTIVE: To assess the efficacy and safety of burosumab in XLH patients, we conducted a systematic review and meta-analysis. METHODS: We searched PubMed, the Cochrane Library, Embase, ClinicalTrials.gov, and Web of Science for studies on the use of burosumab in patients with XLH. Meta-analysis of randomized controlled trials (RCTs) and single-arm trials (SATs) was done to explore burosumab treatment on the efficacy and safety of XLH. RESULTS: Of the 8 eligible articles, 5 were from RCTs and 3 were from SATs. Compared with the control group in RCTs, serum phosphorus level was significantly increased in the burosumab group (0.52 mg/dL, 95% CI 0.24-0.80 mg/dL). A meta-analysis of the burosumab arms in all trials revealed significant increase in serum phosphorus levels (0.78 mg/dL, 95% CI 0.61-0.96 mg/dL), TmP/GFR (0.86 mg/dL, 95% CI 0.60-1.12 mg/dL), and 1,25-dihydroxyvitamin D level (13.23 pg/mL, 95% CI 4.82-21.64 pg/mL) as well. Changes in secondary events also validated the effects of burosumab treatment. Compared with the control group, in RCTs, the safety profile of burosumab is not much different from the control group. Data of the single-arm combined group demonstrated the incidence of any treatment emergency adverse event (TEAE) and the related TEAE rate were high, but the severity of most adverse events is mild to moderate, and the rate of serious TEAE is low. CONCLUSION: This study suggests that burosumab can be an option for patients with XLH and did not significantly increase the incidence of adverse events.

Incidence and predictors of hypophosphataemia after ferric carboxymaltose use-A 3-year experience from a single institution in Singapore.

Ferric carboxymaltose (FCM) administration helps reduce transfusion requirements in the perioperative situation, which improves patient outcomes and reduces healthcare costs. However, there is increasing evidence of hypophosphataemia after FCM use. We aim to determine the incidence of hypophosphataemia after FCM administration and elucidate potential biochemical factors associated with the development of subsequent hypophosphataemia. A retrospective review of anonymised data of all FCM administrations in a single institution was conducted from August 2018 to August 2021. Each unique FCM dose administered was examined to assess its effect on Hb and serum phosphate levels within the subsequent 28 days from each FCM administration. Phosphate levels were repeatedly measured within the 28-day interval and the lowest phosphate level within that period was determined. Patients' serum phosphate levels within 28 days of FCM administration were compared against normal serum phosphate levels within 2 weeks before FCM administration. The odds ratios of various pre-FCM serum markers were calculated to elucidate potential biochemical predictors of post-FCM hypophosphataemia. In 3 years, a total of 1296 doses of FCM were administered to 1069 patients. The mean improvement in Hb was 2.45 g/dL (SD = 1.94) within 28 days of FCM administration, with the mean time taken to peak Hb levels being 6.3 days (SD = 8.63), which is earlier than expected, but was observed in this study and hence reported. The incidence of hypophosphataemia <0.8 mmol/L was 22.7% (n = 186), and <0.4 mmol/L was 1.6% (n = 9). This figure is lower than the numbers reported in previously published meta-analyses given that routine checks of serum phosphate levels were not conducted initially and hence could possibly be higher. The odds of developing hypophosphataemia (<0.8 mmol/L) were 27.7 (CI: 17.3-44.2, p < 0.0001) if baseline serum phosphate was less than 1 mmol/L. The odds of developing hypophosphataemia (<0.8 mmol/L) were 1.3 (CI: 1.08-1.59, p < 0.01) if the change in Hb levels observed after FCM administration were more than 4 g/dL. Hypophosphataemia after FCM administration is significant and FCM should be used by clinicians with caution.

Hypophosphatemia related to intravenous iron therapy with ferric carboxymaltose: A case series.

OBJECTIVES: This case series would like to highlight hypophosphatemia related to ferric carboxymaltose and its adverse clinical consequences. BACKGROUND: Intravenous iron supplementation is a good alternative to oral iron replacement in iron deficiency anaemia due to its ability to correct iron deficit with minimal infusions without incurring the gastrointestinal side effects of oral iron replacement. Ferric carboxymaltose is one common formula for intravenous iron supplementation. However, an increasingly recognised adverse side-effect of intravenous ferric carboxymaltose is hypophosphatemia. There has been increasing reports and studies highlighting hypophosphatemia related to intra-venous iron therapy. Though initially thought to be transient and asymptomatic, recent studies have shown that persistent hypophosphatemia in iron therapy can result in debilitating disease including myopathy, fractures and osteomalacia. METHODS: A retrospective analysis of all patients who had ferric carboxymaltose was performed. RESULTS: We highlight 3 cases where hyposphatemia affected the clinical outcomes. CONCLUSION: With the increased use of IV iron it is important to be aware of the high potential for hypophosphatemia secondary to ferric carboxymaltose.

Interaction between ferric carboxymaltose and denosumab causing severe hypocalcaemia and hypophosphataemia in a patient without chronic kidney disease.

Coadministration of ferric carboxymaltose and denosumab may cause hypocalcaemia and hypophosphataemia; however, this interaction is not well-described in the literature and has typically been described in patients with chronic kidney disease (CKD). We present a case of this interaction in a patient without preexisting CKD. We suggest the use of alternative iron preparations and an interval of at least 4 weeks between administrations.

Iron-induced Hypophosphatemic Osteomalacia-An Atypical Case of Bilateral Femoral Stress Fractures.

We present a case of a 61-year-old healthy man who had bilateral femoral neck insufficiency fractures attributed to repeated iron transfusions, causing iron-induced hypophosphatemic rickets, requiring surgical intervention. Atraumatic insufficiency fractures present a diagnostic dilemma in orthopaedics. Chronic fractures with no acute precipitating trigger can often go unrecognized until complete fracturing or displacement occurs. Early identification of the risk factors in conjunction with a comprehensive history, clinical examination, and imaging can potentially avoid these serious complications. Atraumatic femoral neck insufficiency fractures have been sporadically reported in the literature, often unilateral and attributed to the use of long-term bisphosphonates. Through this case, we elaborate on the relatively unknown link between iron transfusions and insufficiency fractures. This case highlights the importance of early detection and imaging of such fractures from an orthopaedic perspective.

Hypophosphatemic osteomalacia induced by intravenous iron therapy: a case report.

OBJECTIVE: Osteomalacia is an uncommon, overlooked and debilitating metabolic bone disease with numerous aetiologies. Herein, we report an atypical cause of osteomalacia - intravenous iron therapy. METHODS: Description of a case report of hypophophatemic osteomalacia induced by ferric carboxymaltose infusions. RESULTS: A 70-year-old male with Rendu-Osler-Weber syndrome requiring repeated infusions of ferric carboxymaltose was admitted for disabling lower limb pain associated with persistent hypophosphatemia (1.6mg/dL) and increased urinary fractional excretion of phosphate (43%, UP04=118.3mg/dL), serum fibroblast growth factor 23 (324UA/mL), intact parathyroid hormone (110pg/mL) and bone alkaline phosphatase (40.1mcg/L). X-ray and CT of the feet showed severe diffuse bone demineralization. Feet MRI displayed a subchondral fracture of the cuneiform-navicular joints. Spine X-ray revealed dorsolumbar vertebral flattening. Somatostatin receptor PET scan excluded an occult tumor. Bone biopsy with histomorphometry confirmed the presence of osteomalacia. After excluding other causes, a diagnosis of hypophosphatemic osteomalacia induced by frequent ferric carboxymaltose infusions was made. The iron formulation was replaced by saccharated ferric oxide infusions and progressive titration of calcitriol up to 1.5mg/day and oral disodium phosphate up to 5740mg/day was started. After 6 months, there was a clear clinical and analytical improvement. CONCLUSION: Osteomalacia may be a consequence of prolonged hypophosphatemia induced by recurrent ferric infusions, which is an uncommon and neglected bone adverse event of this therapy. Phosphate levels and bone symptoms should be monitored during repetitive iron infusions, maintaining a high level of suspicion for osteomalacia as it is important to identify and treat it in a timely manner, minimizing its severe morbidity.

Simplified regional citrate anticoagulation protocol for CVVH, CVVHDF and SLED focused on the prevention of KRT-related hypophosphatemia while optimizing acid-base balance.

BACKGROUND: Hypophosphatemia is a common electrolyte disorder in critically ill patients undergoing prolonged kidney replacement therapy (KRT). We evaluated the efficacy and safety of a simplified regional citrate anticoagulation (RCA) protocol for continuous venovenous hemofiltration (CVVH), continuous venovenous hemodiafiltration (CVVHDF) and sustained low-efficiency dialysis filtration (SLED-f). We aimed at preventing KRT-related hypophosphatemia while optimizing acid-base equilibrium. METHODS: KRT was performed by the Prismax system (Baxter) and polyacrylonitrile AN69 filters (ST 150, 1.5 m2, Baxter), combining a 18 mmol/L pre-dilution citrate solution (Regiocit 18/0, Baxter) with a phosphate-containing solution (HPO42- 1.0 mmol/L, HCO3- 22.0 mmol/L; Biphozyl, Baxter). When needed, phosphate loss was replaced with sodium glycerophosphate pentahydrate (Glycophos™ 20 mmol/20 mL, Fresenius Kabi Norge AS, Halden, Norway). Serum citrate measurements were scheduled during each treatment. We analyzed data from three consecutive daily 8-h SLED-f sessions, as well as single 72-h CVVH or 72-h CVVHDF sessions. We used analysis of variance (ANOVA) for repeated measures to evaluate differences in variables means (i.e. serum phosphate, citrate). Because some patients received phosphate supplementation, we performed analysis of covariance (ANCOVA) for repeated measures modelling phosphate supplementation as a covariate. RESULTS: Forty-seven patients with acute kidney injury (AKI) or end stage kidney disease (ESKD) requiring KRT were included [11 CVVH, 11 CVVHDF and 25 SLED-f sessions; mean Acute Physiology and Chronic Health Evaluation II (APACHE II) score 25 ± 7.0]. Interruptions for irreversible filter clotting were negligible. The overall incidence of hypophosphatemia (s-P levels <2.5 mg/dL) was 6.6%, and s-P levels were kept in the normality range irrespective of baseline values and the KRT modality. The acid-base balance was preserved, with no episode of citrate accumulation. CONCLUSIONS: Our data obtained with a new simplified RCA protocol suggest that it is effective and safe for CVVH, CVVHDF and SLED, allowing to prevent KRT-related hypophosphatemia and maintain the acid-base balance without citrate accumulation. TRIAL REGISTRATION: NCT03976440 (registered 6 June 2019).

[Hypophosphatemia after injectable iron treatments in adults: Comparison between ferric carboxymaltose and iron sucrose]. / Hypophosphorémie après traitement par fer injectable chez l'adulte : comparaison entre le carboxymaltose ferrique et l'hydroxyde ferrique-saccharose.

Hypophosphatemia is a recognized side effect of treatment of iron deficiency anemias with injectable iron. We analyzed 35 clinical trials that used ferric carboxymaltose (FCM) or iron sucrose (IS). Hypophosphatemia prevalence ranged from 0 to 91.7%. FCM-induced a significant (P<0.001) greater hypophosphatemia prevalence and phosphatemia decrease than IS (52.0% [95% CI: 42.2-61.8%] vs. 7.7% [95% CI: -2.8 to 18.2%] and -1.12mmol/L [95% CI: -1.36 to -0.89mmol/L] vs. -0.13mmol/L [95% CI: -0.59 to 0.32mmol/L]). FCM-induced hypophosphatemia was dose-dependent. The nadir of hypophosphatemia was reached in almost all studies after 7 and 14days. Hypophosphatemia persisted at the end of the study in 53.8% of the reported studies that used FCM and lasted up to 6months. FCM-induced an increase in intact circulating fibroblast growth factor 23 and in renal phosphorus excretion while serum 1-25 dihydroxyvitamin D was decreased. Risk factors for hypophosphatemia after FCM therapy were low basal circulating phosphate or ferritin, low body weight, high glomerular filtration rate, serum parathyroid hormone or hemoglobin and age, whereas renal insufficiency was associated with a lower risk. In conclusion, hypophosphatemia is common after treatment with injectable iron, FCM being associated with a higher risk than IS and with disorders of phosphocalcium metabolism. Monitoring of blood phosphate and 1-25 dihydroxyvitamin D could be considered during FCM therapy.

Estimation of the utilities of attributes of intravenous iron infusion treatment for patients with iron-deficiency anemia: a conjoint analysis in Japan.

AIMS: This study aimed to estimate the utility values of the factors associated with intravenous (IV) iron infusion treatment in Japanese patients with iron-deficiency anemia (IDA) from the patient's perspective. METHODS: A conjoint analysis based on online survey data was conducted in May 2022 (registration number: UMIN000047756). Respondents in the main group were selected from the general population (20-69 years). Seven attributes were included in this analysis: waiting time before receiving an IV infusion, pain due to IV infusion, time required for IV infusion, number of IV infusions required to achieve treatment effect, frequency of hypophosphatemia as a side effect of IV infusion, frequency of skin discoloration by the drug solution, and out-of-pocket cost for one IV infusion visit. The utility of each level for each attribute was estimated using a logistic regression model as the difference from non-treatment. RESULTS: The responses were collected from 1,026 people. The utilities decreased with higher pain (-0.189 for pain level of 3.05), longer time for the IV infusion (-0.145 or -0.212 for 5 or 15 min), greater number of required IV infusions (-0.773 or -1.899 for 3 or 25 times), and higher frequency of adverse events (-0.373 or -0.385 for 13.0% or 14.2% of hypophosphatemia incidences; -0.502 for 2.3% of skin discoloration per one infusion). LIMITATIONS: Since this study was based on an online survey, the reliability of the results depends on whether the respondents understood the questions accurately. Further, the respondents were selected from an online panel, potentially affecting finding generalizability. CONCLUSIONS: The results indicate that utilities differ depending on the factors associated with IV iron infusion treatment. The findings of this study may be useful for informing future treatments or improving current treatment regimes, supporting the achievement of complete iron repletion for Japanese patients with IDA.

Incidence, evolution and risk factors of hypophosphatemia in patients with solid tumors receiving ferric carboxymaltose: a retrospective cohort study.

OBJECTIVES: Ferric carboxymaltose (FCM) is increasingly used in the management of cancer-related anemia, yet it may cause hypophosphatemia. This retrospective study describes the incidence, evolution and risk factors of hypophosphatemia in a cohort of patients with solid tumors receiving FCM. METHODS: Serum phosphorus concentration was assessed longitudinally using a random intercepts model. The probability of developing hypophosphatemia, as graded by CTCAE version 4.0, was investigated using a multi-state model. Transition hazards were modeled non-parametrically and semi-parametrically by a Cox model. Causal marginal risk differences between baseline interventions on serum phosphorus and/or FCM dose were obtained via G-computation. RESULTS: In 174 ambulatory patients with solid tumors receiving FCM at two university hospitals between October 2020 and September 2021, the risk of developing moderate-to-severe hypophosphatemia was 36.0% (95% confidence interval (CI) 28.2-43.9%) and peaked within 16 days after first FCM administration. The average duration of moderate-to-severe hypophosphatemia was 12.4 days. After adjustment for confounders, lower baseline serum phosphorus (adjusted hazard ratio (aHR) 0.88 per 0.1 mmol/L increase, 95% CI 0.79-0.98) and higher FCM dose (first dose: aHR 1.12 per 1 mg/kg increase, 95% CI 1.01-1.25; second dose: aHR 1.06 per 1 mg/kg increase, 95% CI 1.00-1.13) significantly increased the hazard of moderate-to-severe hypophosphatemia. CONCLUSION: Approximately one out of three ambulatory patients with solid tumors may develop moderate-to-severe hypophosphatemia after FCM administration. Baseline serum phosphorus and FCM dose may be modifiable risk factors that should be considered for intervention in order to mitigate the risk of hypophosphatemia.

Improvement in the mobility of a patient with fibroblast growth factor 23-related hypophosphatemic osteomalacia and decompensated liver cirrhosis in response to burosumab: a case report.

Acquired fibroblast growth factor (FGF) 23-related hypophosphatemic osteomalacia is characterized clinically by muscle weakness, bone pain, and fractures. Its biochemical features include hypophosphatemia, caused by renal phosphate wasting, and inappropriately normal or low 1,25-dihydroxy-vitamin D levels. Recently, burosumab, a fully human monoclonal antibody targeting FGF23, was approved for the treatment of FGF23-related hypophosphatemic rickets and osteomalacia. We report the case of a 75-year-old Japanese woman with decompensated liver cirrhosis and hepatic encephalopathy, caused by primary biliary cholangitis, who complained of back pain and limited mobility resulting from multiple vertebral fractures. She was not receiving iron infusion therapy and denied alcohol consumption. The patient exhibited hypophosphatemia with a low tubular maximum reabsorption of phosphate per unit glomerular filtration rate (TmP/GFR) and a high circulating concentration of FGF23. Conventional therapy with alfacalcidol and oral phosphate slightly improved her serum phosphate concentration and back pain, but she experienced a hip fracture, causing her to become wheelchair-dependent. Burosumab was initiated 8 weeks after the hip fracture, which increased her serum phosphate concentration and TmP/GFR. Her mobility gradually improved, such that she could walk without a cane after 16 weeks of treatment. Her lumbar bone mineral density increased after 48 weeks. Hepatic encephalopathy developed once before the initiation of treatment and twice after the initiation of the therapy, but her liver function was preserved. This is the first study to report the efficacy and safety of burosumab treatment for FGF23-related hypophosphatemic osteomalacia with decompensated liver cirrhosis.