Rare renal proximal tubular dysfunctions in primary biliary cholangitis

INTRODUCTION

Renal involvement of primary biliary cholangitis (PBC) usually presents as distal renal tubular acidosis. Proximal tubular (PT) dysfunctions in PBC were rarely reported with unclear clinicopathological characteristics and renal prognosis.

METHODS

We identified 11 cases of PBC with PT dysfunctions (PBC-PT). Their medical document, kidney pathology, and follow-up data were retrospectively reviewed and analyzed.

RESULTS

The 11 PBC-PT patients were mainly middle-aged (57.8 ± 5.2 years) females (81.8%). Most of them were asymptomatic PBC (7, 63.6%) with a high prevalence of elevated serum immunoglobulin M (IgM, 81.8%) and G (IgG, 54.5%) levels. In the kidney, they had a mean estimated glomerular filtration rate (eGFR) level of 46.54 ± 23.03 ml/min/1.73m2, and 81.8% of them had eGFR below 60 ml/min/1.73m2. They showed different degrees of PT dysfunctions, including hyperuricosuria, hypouricemia, normoglycemic glycosuria, generalized aminoaciduria, hyperphosphaturia, and hypophosphatemia. Their kidney pathology showed tubulointerstitial nephritis with lymphoplasmacytic infiltrates, brush border defects, and proximal tubulitis. After glucocorticoids treatment, the PT dysfunctions manifesting as hypophosphatemia, hypouricemia, and renal glycosuria all recovered, and the eGFR levels were improved from 43.24 ± 19.60 ml/min/1.73m2 to 55.02 ± 21.14 ml/min/1.73m2 (p = 0.028), accompanied by significant improvements of serum IgM levels (from 5.97 ± 4.55 g/L to 2.09 ± 1.48 g/L, p = 0.019).

CONCLUSIONS

The PT dysfunctions were rare in PBC patients, and glucocorticoids treatment could benefit the improvements of eGFR and tubular functions.

Hypophosphatemia as a Predictor of Clinical Outcomes in Acute Pancreatitis: A Retrospective Study

OBJECTIVE

Phosphate is crucial for cellular repair after injury and may be important in recovery following acute pancreatitis (AP). This study aimed to evaluate the association between hypophosphatemia and severity of AP.

METHODS

Patients admitted with AP between 2014-2018 were identified and their records were retrospectively reviewed. Pancreatitis severity was defined using the modified Atlanta Criteria. Hypophosphatemia was defined as phosphate <2 mg/dL and was assessed at three time points: within one day, within two days, at any time during admission. The proportion of patients who developed severe AP was compared between patients with and without hypophosphatemia.

RESULTS

Of 312 patients, 30.1% (n = 94) developed severe AP. Hypophosphatemia occurred in 25.0% overall, within one day in 19.7%, and within two days in 20.0%. A higher proportion of patients with hypophosphatemia developed severe AP (overall: 47.4% vs. 24.4%, P < 0.001; one day: 47.4% vs. 23.9%, P = 0.004; two days: 42.9% vs. 24.5%, P = 0.01). Patients with hypophosphatemia within one day were also more likely to have ICU admission ( P < 0.001) and longer length of stay ( P < 0.001).

CONCLUSIONS

Early hypophosphatemia during an admission for AP was associated with increased AP severity, ICU admission, and longer length of stay.

Cost-utility analysis of ferric derisomaltose versus ferric carboxymaltose in patients with inflammatory bowel disease and iron deficiency anemia in England

AIMS

Anemia is the most common extraintestinal complication of inflammatory bowel disease (IBD), with approximately half of cases caused by iron deficiency (ID). Intravenous iron is the preferred ID anemia (IDA) treatment where oral iron is contraindicated, ineffective or not tolerated, or where ID correction is urgent. The objective was to evaluate the cost-utility of ferric derisomaltose (FDI) versus ferric carboxymaltose (FCM) in patients with IBD and IDA in England, in whom IV iron treatment is preferred.

MATERIALS AND METHODS

A patient-level simulation model was developed, capturing quality of life (QoL) differences based on SF-36v2 data from the PHOSPHARE-IBD randomized controlled trial, monitoring and incidence of post-infusion hypophosphatemia, and number of iron infusions required. Analyses were conducted over a five-year time horizon from the Department of Health and Social Care (DHSC) perspective, with healthcare provider and societal perspectives adopted in separate analyses. Future costs and effects were discounted at 3.5% per annum and one-way and probabilistic sensitivity analyses were performed.

RESULTS

FDI increased quality-adjusted life expectancy by 0.075 QALYs versus FCM from 2.57 QALYs to 2.65 QALYs per patient. Patients receiving FDI required 1.63 fewer iron infusions over the five-year time horizon, driving infusion-related cost savings of GBP 496 per patient (GBP 2,188 versus GBP 1,692) from the DHSC perspective. Costs of monitoring and treating hypophosphatemia after FCM were GBP 226, yielding total savings of GBP 722 per patient (GBP 2,414 versus GBP 1,692) over the five-year time horizon. FDI also led to reduced costs versus FCM in the societal and provider analyses and was therefore the dominant intervention across all three perspectives.

LIMITATIONS

The analysis did not capture patient adherence, hypophosphatemic osteomalacia, or fractures.

CONCLUSIONS

Results showed that FDI improved patient QoL and reduced direct healthcare expenditure versus FCM in patients with IBD and IDA in England.

Marked increase in bone mineral density with oral phosphate and calcitriol in tumour-induced osteomalacia

Patients with osteomalacia have a low bone mineral density (BMD) and are often misdiagnosed as osteoporosis. A marked increase in BMD is noticed following successful treatment of osteomalacia. The biochemical hallmark of tumour-induced osteomalacia (TIO) is hypophosphatemia. Patients with TIO often have severe hypophosphatemic osteomalacia and dual-energy X-ray absorptiometry may demonstrate low BMD. Surgical removal of the phosphatonin-secreting lesion restores serum phosphate, corrects osteomalacia and is associated with a dramatic increase in BMD. We report two patients with TIO and low BMD, who were treated with oral phosphate and calcitriol supplementation. The percentage increase in BMD at 33 months was as high as 94.3% in areas with the lowest BMD at baseline. The BMD at 33 months was higher than the +2SD of the population-specific reference ranges, a finding not reported in surgically treated patients with TIO. An intermittent rise in parathyroid hormone following oral phosphate supplementation might have resulted in such findings.

Refeeding Syndrome in Pediatric Age, An Unknown Disease: A Narrative Review

Refeeding syndrome (RS) is characterized by electrolyte imbalances that can occur in malnourished and abruptly refed patients. Typical features of RS are hypophosphatemia, hypokalemia, hypomagnesemia, and thiamine deficiency. It is a potentially life-threatening condition that can affect both adults and children, although there is scarce evidence in the pediatric literature. The sudden increase in food intake causes a shift in the body's metabolism and electrolyte balance, leading to symptoms such as weakness, seizures, and even heart failure. A proper management with progressive increase in nutrients is essential to prevent the onset of this condition and ensure the best possible outcomes. Moreover, an estimated incidence of up to 7.4% has been observed in pediatric intensive care unit patients receiving nutritional support, alone or as an adjunct. To prevent RS, it is important to carefully monitor feeding resumption, particularly in severely malnourished individuals. A proper strategy should start with small amounts of low-calorie fluids and gradually increasing the calorie content and amount of food over several days. Close monitoring of electrolyte levels is critical and prophylactic use of dietary supplements such as thiamine may be required to correct any imbalances that may occur. In this narrative review, we aim to provide a comprehensive understanding of RS in pediatric clinical practice and provide a possible management algorithm.

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.

Mutations of family with sequence similarity 20-member C gene causing lethal and nonlethal Raine syndrome causes hypophosphatemia rickets

Family with sequence similarity 20-member C (FAM20C) is a kinase specific to most of the secreted phosphoproteome. FAM20C has been identified as the causative gene of Raine syndrome, initially characterized by lethal osteosclerosis bone dysplasia. However, since the identification of the cases of nonlethal Raine syndrome characterized by hypophosphatemia rickets, the previous definition of Raine syndrome has become debatable and raised a question about the role of mutations of FAM20C in controversial skeletal manifestation in the two forms of the disease. In this study, we aimed to investigate the influence of FAM20C mutations on skeletogenesis. We developed transgenic mice expressing Fam20c mutations mimicking those associated with human lethal and nonlethal Raine syndrome. The results revealed that transgenic mice expressing the mutant Fam20c found in the lethal (KO;G374R) and nonlethal (KO;D446N) Raine syndrome exhibited osteomalacia without osteosclerotic features. Additionally, both mutants significantly increased the expression of the Fgf23, indicating that Fam20c deficiency in skeletal compartments causes hypophosphatemia rickets. Furthermore, as FAM20C kinase activity catalyzes the phosphorylation of secreted proteomes other than those in the skeletal system, global FAM20C deficiency may trigger alterations in other systems resulting in osteosclerosis secondary to hypophosphatemia rickets. Together, the findings of this study suggest that FAM20C deficiency primarily causes hypophosphatemia rickets or osteomalacia; however, the heterogeneous skeletal manifestation in Raine syndrome was not determined solely by specific mutations of FAM20C. The findings also implicated that rickets or osteomalacia caused by FAM20C deficiency would deteriorate into osteosclerosis by the defects from other systems or environmental impacts.

X-Linked Familial Hypophosphatemia: A Case Report of 27-Year Old Male and Review of Literature

X-linked hypophosphatemia (XLH) associated with short stature during childhood are mostly referred to the hospital and diagnosed as vitamin D deficiency rickets and received vitamin D before adulthood. A case is presented with clinical features of hypophosphatemia from childhood who did not seek medical care for diagnosis and treatment, nor did his mother or two brothers, who have short statures, bone pain, and fractures. The patient was assessed for sociodemographic, hematological, and biochemical parameters together with a genetic assessment. A DEXA scan and X-ray were done to determine the abnormalities and deformities of joints and bones despite clinical examination by an expert physician. All imaging, laboratory parameters, and the genetic study confirmed the diagnosis of XLH. A detailed follow-up of his condition was performed after the use of phosphate tablets and other treatments. X-linked hypophosphatemia needs a good assessment, care, and follow up through a complementary medical team including several specialties. Phosphate tablets in adulthood significantly affects clinical and physical improvement and prevention of further skeletal abnormality and burden on daily activity. The patients should be maintained with an adequate dose of phosphate for better patient compliance. More awareness is needed in society and for health professionals when conducting medical checkups during the presence of stress fractures, frequent dental and gum problems, rickets, short stature, or abnormality in the skeleton or walking to think of secondary causes such as hypophosphatemia. Further investigations including a visit to a specialist is imperative to check for the primary cause of these disturbances.

Hypophosphatemia in infants with severe bronchiolitis and association with length of mechanical ventilation

OBJECTIVES

Electrolyte disorders occurs frequently in children with bronchiolitis. The aim of the present study was to describe the frequency of hypophosphatemia and to evaluate its association with length of mechanical ventilation in infants admitted to a pediatric intensive care unit (PICU) with bronchiolitis.

METHODS

This retrospective cohort study included infants aged between 7 days and 3 months admitted to a PICU between September 2018 and March 2020 and diagnosed with severe acute bronchiolitis requiring respiratory support. Infants with a chronic condition that could potentially be a confounding factor were excluded. The primary outcome was the frequency of hypophosphatemia (<1.55 mmol/L); the secondary outcomes were the frequency of hypophosphatemia during the PICU stay, and the association with length of mechanical ventilation (LOMV).

RESULTS

Among the 319 infants admitted 178 had at least one phosphatemia value and were included in the study. The frequency of hypophosphatemia was 41% at PICU admission (61/148) and 46% during the PICU stay (80/172). The median [IQR] LOMV was significantly longer in children with hypophosphatemia at admission (109 [65-195] h vs. 67 [43-128] h, p = 0.007), and in multivariable linear regression lower phosphatemia at admission was associated with longer LOMV (p < 0.001) after controlling for severity (PELOD2 score) and weight.

CONCLUSION

Hypophosphatemia was frequent in infants with severe bronchiolitis admitted to a PICU and was associated with a longer LOMV.

Osmotic demyelination syndrome: novel risk factors and proposed pathophysiology

BACKGROUND

Osmotic demyelination syndrome (ODS) is non-inflammatory demyelination in response to an osmotic challenge. It can be pontine or extrapontine in presentation.

AIMS

To retrospectively review cases involving ODS and define the spectrum of causes, risk factors, clinical and radiological presentations, and functional outcomes.

RESULTS

The study utilised data from 15 patients with a mean age of 53.6 years. Malnutrition (9; 60%) and chronic alcoholism (10; 66.7%) were the most common associated disorders. Two (13.3%) patients had severe hyponatraemia (<120 mmol/L). The average highest single-day change was 5.1 mmol/L. Radiologically, 14 (93.3%) had pontine and 6 (40%) had extra-pontine lesions. Hypokalaemia (14; 93.3%) and hypophosphataemia (9; 60%) were commonly associated. Common clinical manifestations include altered consciousness/encephalopathy (9; 60%), dysphagia (4; 26.7%) and limb weakness (4; 26.7%). At 3 months, two (14.3%) had died and six (40%) were functionally independent (modified Rankin scale 0-2).

CONCLUSION

We found that ODS occurred despite appropriate correction rates of hyponatraemia. Factors such as malnutrition, chronic alcoholism, hypokalaemia and hypophosphataemia are thought to play a role in its pathogenesis. Approximately half of the patients survived and became functionally independent.

Unpredictable refeeding syndrome with severe hypophosphatemia in borderline personality disorder comorbidity: A case report

RATIONALE

Refeeding syndrome (RS) is a fatal condition caused by rapid calorie intake during starvation. Self-neglected fasting in psychiatric disorders is associated with RS. However, overeating resulting from circumventing the clinician's instructions does not have a reportedly high risk of RS.

PATIENT CONCERNS

A 47-year-old undernourished woman with borderline personality disorder was hospitalized for nausea, vomiting, and diarrhea.

CLINICAL FINDINGS

She had not eaten much for 10 days and had lost weight (56.5-51.1 kg) over 3 weeks. No abnormalities were indicated on physical examination and imaging examinations.

DIAGNOSES, INTERVENTIONS, AND OUTCOMES

Infectious diseases and malignancies were excluded from the differential diagnosis. On the third day of admission, the patient's serum phosphorus level significantly decreased to 0.7 mg/dL, and additional sodium phosphate was administered intravenously. On the fourth day, despite our instructions, the patient was found to be eating nonhospital food from the first day of admission. In conjunction with her history, a final diagnosis of RS was made. After appropriate treatments, the patient was discharged on the 15th day of hospitalization. The patient's nausea, vomiting, and diarrhea were improved.

LESSONS

When undernourished patients have psychiatric disorders, including borderline personality disorder or schizophrenia, the occurrence of RS should be considered based on the patients' poor adherence to physicians' instructions.

Hypophosphataemia risk associated with ferric carboxymaltose in heart failure: A pooled analysis of clinical trials

AIMS

Iron deficiency is a common finding among patients with heart failure (HF) and is associated with adverse outcomes, including decreased quality of life, increased risk of hospitalization, and decreased survival. Intravenous ferric carboxymaltose (FCM) has been shown to improve outcomes among patients with HF and concomitant iron deficiency, but FCM is associated with an increased risk of hypophosphataemia. We aimed to better characterize this risk among HF populations.

METHODS AND RESULTS

This pooled analysis examined data from 41 studies of adults with iron deficiency across disease states and therapeutic areas. Among the 7931 patients treated with FCM available for analysis, 14% made up the HF subgroup. Additional subgroups included women's health (36%), non-dialysis-dependent chronic kidney disease (NDD-CKD; 27%), haemodialysis-dependent chronic kidney disease (HD-CKD; 1%), gastrointestinal (10%), neurology (3%), and other (10%). The incidence of post-baseline moderate or severe hypophosphataemia (i.e. serum phosphate [PO4 3- ] level <2.0 mg/dL) varied across the therapeutic areas, with the lowest incidences observed in the HD-CKD (0%), HF (8.1%), and NDD-CKD (12.8%) subgroups. The prevalence of moderate or severe hypophosphataemia among the women's health, other, gastrointestinal, and neurology subgroups was 30.1%, 40.6%, 51.0%, and 55.6%, respectively. In the HF subgroup, one patient (<0.1%) had a serum PO4 3- of <1.0 mg/dL recorded, compared with 4.8% and 4.0% of the subjects in the neurology and gastrointestinal groups, respectively. With the exception of the HD-CKD subgroup, mean serum PO4 3- levels decreased through weeks 2 to 4, and then returned toward baseline and plateaued by week 8. The strongest predictor of hypophosphataemia was preserved kidney function (estimated glomerular filtration rate: >60 mL/min/1.73 m2 vs. <30 mL/min/1.73 m2 ; odds ratio: 12.2). Among patients in the HF subgroup, the incidence of treatment-emergent adverse events potentially related to hypophosphataemia (e.g. cardiac failure, ventricular tachyarrhythmias, fatigue, muscle weakness, bone pain, neurological symptoms, and muscle pain) was lower among FCM-treated patients than among those receiving placebo, and lower among patients with a post-baseline PO4 3- <2 mg/dL vs. those not meeting such criteria.

CONCLUSIONS

The risk of laboratory-assessed hypophosphataemia in HF patients treated with FCM was lower than that seen in patients in other therapeutic areas treated with FCM, and clinical events associated with hypophosphataemia are uncommon with FCM therapy in this population. Appropriate monitoring, particularly soon after administration in the unlikely event of repeated dosing in HF patients, will allow for further refinement of management strategies. [Correction added on 24 February 2023, after first online publication: In the preceding sentence, "…administration, will allow…" has been corrected to "…administration in the unlikely event of repeated dosing in HF patients, will allow…" in this version.].

Impact of Nutritional Management on Survival of Critically Ill Malnourished Patients with Refeeding Hypophosphatemia

BACKGROUND

Early nutritional therapy may aggravate hypophosphatemia in critically ill patients.

AIM

To investigate the influence of the type nutritional therapy on the survival of critically-ill malnourished patients at refeeding hypophosphatemia risk.

METHODS

Retrospective cohort study including malnourished, critically-ill adults, admitted from June 2014-December 2017 in an intensive care unit (ICU) at a tertiary hospital. Refeeding hypophosphatemia risk was defined as low serum phosphorus levels (<2.5 mg/dL) seen at two timepoints: before the initiation and at day 4 of the nutritional therapy. Patients receiving enteral nutrition (EN) were compared with those receiving supplemental parenteral nutrition (SPN-EN plus parenteral nutrition). Primary outcome was 60 d survival. Secondary endpoint was the incidence of refeeding hypophosphatemia risk.

RESULTS

We included 468-321 patients (68.6%) received EN and 147 (31.4%) received SPN. The mortality rate was 36.3% (n = 170). Refeeding hypophosphatemia risk was found in 116 (24.8%) patients before and in 177 (37.8%) at day 4 of nutritional therapy. The 60 d mean survival probability was greater for patients receiving SPN both before (42.4 vs. 22.4%, p = 0.005) and at day 4 (37.4 vs. 25.8%, p = 0.014) vs. patients receiving EN at the same timepoints. Cox regression showed a hazard ratio of 3.3 and 2.4 for patients at refeeding hypophosphatemia risk before and at day 4 of EN, respectively, compared to the SPN group at the same timepoints.

CONCLUSION

Refeeding hypophosphatemia risk was frequent in malnourished ICU patients and the survival for patients receiving SPN seemed associated with better survival than EN only.

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.

Total hip arthroplasty for treatment of femoral neck fracture due to hypophosphatemic osteomalacia: a retrospective case series with mean follow-up of five years

BACKGROUND

To retrospectively characterize the clinical characteristics and efficacy of total hip arthroplasty and the important factors needing attention in hypophosphatemic osteomalacia (HO) patients with hip involvement.

PATIENTS AND METHODS

We performed a review of seven patients (two women and five men) referred to our clinic with a final diagnosis of HO who received total hip arthroplasty between 2010 and 2018. Five patients (Group 1) received proper medical management with or without aetiologic therapy, while the other two patients (Group 2) did not receive due to misdiagnosis. The mean follow-up duration was 5.1 ± 2.0 years.

RESULTS

The patients in Group 1 had significant relief of pain and improved laboratory results. The mean Harris Hip Score of Group 1 increased from 44.2 ± 6.0 to 94.0 ± 3.0, and the mean VAS score decreased from 8.8 ± 0.4 to 1.8 ± 0.7. However, the progressive extensive pain score in Group 2 had no obvious improvement, with the Harris Hip Score increasing from 45.5 ± 0.5 to 60 ± 28.0 and the VAS score decreasing from 9.0 ± 1.0 to 6.5 ± 2.5.

CONCLUSION

THA appears to be an effective method for hip arthritis or joint deformities resulting from hypophosphatemic osteomalacia. A satisfactory outcome of the surgery depends on the early etiological identification, the treatment of hypophosphatemia, a careful operation, and the operative strategies, as well as proper medical treatment.

[Tumor-induced osteomalacia caused by an orbital tumor: a case report]

A 52-year-old patient was initially diagnosed as hypophosphatemic osteomalacia in the Department of Endocrinology due to knee, foot and lumbosacral pain. The symptoms were not significantly relieved after phosphorus and vitamin D supplementation. Later, the imaging examination showed an orbital tumor in the right eye. The tumor was surgically removed, and the symptoms of systemic bone pain were relieved.

Hungry bone syndrome like presentation following single-dose denosumab for hypercalcaemia secondary to sarcoidosis with IgA nephropathy

A woman in her mid-50s with IgA nephropathy, sarcoidosis and steroid-induced diabetes mellitus presented with generalised paraesthesia and spontaneous tetany. She had received denosumab 60 mg subcutaneously 8 weeks previously for parathyroid hormone independent hypercalcaemia.At admission, she had severe hypocalcaemia (5 mg/dL), hypophosphataemia (1.9 mg/dL), hypomagnesaemia (1.4 mg/dL) and elevated serum creatinine (1.48 mg/dL) with prolonged QTc (corrected QT interval) on electrocardiograph. She initially received intravenous calcium and magnesium followed by oral calcium carbonate and calcitriol. Her prednisolone dose was tapered to 5 mg/day. Evaluation showed secondary hyperparathyroidism (1474 pg/mL) and elevated 1,25-dihydroxy vitamin D (195 pg/mL). After 1 week of oral calcium carbonate (3000 mg/day) and calcitriol (1.5 µg/day), she achieved normocalcaemia (8.1 mg/dL).To conclude, denosumab for hypercalcaemia with renal insufficiency causes prolonged severe symptomatic hypocalcaemia and hypophosphataemia mimicking hungry bone syndrome. It is important to periodically monitor for hypocalcaemia after denosumab.

Hypophosphatemia after intravenous iron therapy: Comprehensive review of clinical findings and recommendations for management

Contemporary intravenous iron formulations allow administration of high doses of elemental iron and enable correction of total iron deficit in one or two infusions. An important but underappreciated complication of certain formulations is hypophosphatemia caused by increased secretion of the phosphaturic hormone, fibroblast growth factor 23 (FGF23). The pathophysiology of FGF23-induced hypophosphatemia due to certain intravenous iron formulations has been recently investigated in prospective clinical trials. To reach the correct diagnosis, clinicians must recognize the typical clinical manifestations of intravenous iron-induced hypophosphatemia and identify a specific pattern of biochemical changes (hyperphosphaturic hypophosphatemia triggered by high FGF23 that causes low 1,25 (OH)₂ vitamin D, hypocalcemia and secondary hyperparathyroidism). Physicians and patients should be aware of hypophosphatemia as a common complication of intravenous iron therapy and monitor serum phosphate concentrations in patients receiving repeated doses of specific intravenous iron formulations. Symptoms of hypophosphatemia are associated with severity and duration. Persistent hypophosphatemia can occur with iron therapy and can cause debilitating diseases including myopathy, osteomalacia and fractures. This review summarizes the current understanding of the iron-phosphate axis as well as complications of intravenous iron-induced hypophosphatemia.

Significance of Hypophosphatemia in Patients with Pneumonia

Objective Phosphate is a fundamental element involved in a number of physiological pathways. A previous study showed abnormal laboratory findings and a higher mortality in hypophosphatemic patients than in normophosphatemic patients with pneumonia. Sporadic cases of pneumonia due to Legionella spp., Streptococcus pneumoniae, and viruses have been reported; however, the significance of hypophosphatemia in patients with pneumonia has not been adequately studied. We determined whether or not hypophosphatemia in patients with community-acquired pneumonia (CAP) was associated with specific pathogens, patient factors, disease severity, and mortality. Method We retrospectively analyzed 600 patients with CAP who were admitted to our hospital between January 1, 2010, and December 31, 2019. Results Hypophosphatemia was found in 72 (12.0%) of the 600 patients. The most frequent causative microbial agents of CAP in patients with hypophosphatemia were S. pneumoniae, Legionella spp., and influenza virus, whereas in severely ill patients with hypophosphatemia, influenza virus was the most common. Legionella spp., diabetes mellitus, and severe pneumonia were the independent factors for hypophosphatemia in the multivariable analysis. An impaired performance status, severe status on admission, interstitial pneumonia, bacteremia, and guideline-discordant therapy were the independent factors associated with mortality in the multivariable analysis. Hypophosphatemia was not significantly associated with mortality but showed a trend towards higher mortality in the multivariable analysis. Conclusion Hypophosphatemia was not associated with the prognosis in patients with CAP. However, the significance of hypophosphatemia for clinicians lies in the laboratory findings that predict abnormal glucose metabolism, Legionella infection, and severe disease.

The Role of Phosphate in Alcohol-Induced Experimental Pancreatitis

BACKGROUND & AIMS

Heavy alcohol consumption is a common cause of acute pancreatitis; however, alcohol abuse does not always result in clinical pancreatitis. As a consequence, the factors responsible for alcohol-induced pancreatitis are not well understood. In experimental animals, it has been difficult to produce pancreatitis with alcohol. Clinically, alcohol use predisposes to hypophosphatemia, and hypophosphatemia has been observed in some patients with acute pancreatitis. Because of abundant protein synthesis, the pancreas has high metabolic demands, and reduced mitochondrial function leads to organelle dysfunction and pancreatitis. We proposed, therefore, that phosphate deficiency might limit adenosine triphosphate synthesis and thereby contribute to alcohol-induced pancreatitis.

METHODS

Mice were fed a low-phosphate diet (LPD) before orogastric administration of ethanol. Direct effects of phosphate and ethanol were evaluated in vitro in isolated mouse pancreatic acini.

RESULTS

LPD reduced serum phosphate levels. Intragastric administration of ethanol to animals maintained on an LPD caused severe pancreatitis that was ameliorated by phosphate repletion. In pancreatic acinar cells, low-phosphate conditions increased susceptibility to ethanol-induced cellular dysfunction through decreased bioenergetic stores, specifically affecting total cellular adenosine triphosphate and mitochondrial function. Phosphate supplementation prevented ethanol-associated cellular injury.

CONCLUSIONS

Phosphate status plays a critical role in predisposition to and protection from alcohol-induced acinar cell dysfunction and the development of acute alcohol-induced pancreatitis. This finding may explain why pancreatitis develops in only some individuals with heavy alcohol use and suggests a potential novel therapeutic approach to pancreatitis. Finally, an LPD plus ethanol provides a new model for studying alcohol-associated pancreatic injury.

Consensus Recommendations for the Diagnosis and Management of X-Linked Hypophosphatemia in Belgium

X-linked hypophosphatemia (XLH) is the most common genetic form of hypophosphatemic rickets and osteomalacia. In this disease, mutations in the PHEX gene lead to elevated levels of the hormone fibroblast growth factor 23 (FGF23), resulting in renal phosphate wasting and impaired skeletal and dental mineralization. Recently, international guidelines for the diagnosis and treatment of this condition have been published. However, more specific recommendations are needed to provide guidance at the national level, considering resource availability and health economic aspects. A national multidisciplinary group of Belgian experts convened to discuss translation of international best available evidence into locally feasible consensus recommendations. Patients with XLH may present to a wide array of primary, secondary and tertiary care physicians, among whom awareness of the disease should be raised. XLH has a very broad differential-diagnosis for which clinical features, biochemical and genetic testing in centers of expertise are recommended. Optimal care requires a multidisciplinary approach, guided by an expert in metabolic bone diseases and involving (according to the individual patient's needs) pediatric and adult medical specialties and paramedical caregivers, including but not limited to general practitioners, dentists, radiologists and orthopedic surgeons. In children with severe or refractory symptoms, FGF23 inhibition using burosumab may provide superior outcomes compared to conventional medical therapy with phosphate supplements and active vitamin D analogues. Burosumab has also demonstrated promising results in adults on certain clinical outcomes such as pseudofractures. In summary, this work outlines recommendations for clinicians and policymakers, with a vision for improving the diagnostic and therapeutic landscape for XLH patients in Belgium.

Hypophosphatemic Hypovitaminosis D Induces Osteomalacia in the Adult Female Rat

Osteomalacia is a bone-demineralizing disease of adulthood, often caused by hypovitaminosis D. Current animal models of the disease mimic osteomalacia as a consequence of gastric bypass or toxic exposure to metals, but a relevant model of diet-induced osteomalacia is lacking. For that purpose, 7-month-old female Sprague Dawley rats were randomly assigned into 2 weight-stratified groups and maintained for 4 months on synthetic diets containing negligible or normal levels of vitamin D. The dietary regimen resulted in vitamin D deficiency as measured by 25-hydroxyvitamin D serum levels; however, hypovitaminosis D per se did not affect biomarkers of calcium metabolism and bone turnover, nor did it result in increased osteoid. Thus, vitamin D depletion through the diet was found to be insufficient to induce an osteomalacia-like phenotype in the adult rat. After 4 months, the phosphate content of the vitamin D-depleted diet had decreased to 0.16% (calcium:phosphorus ratio of 5.85), resulting in an osteomalacic-like condition (trabecular osteoid surface/bone surface constituted 33%; CI, 26-40). The diet change also affected both metabolic and bone turnover biomarkers, including significantly suppressing serum fibroblast growth factor 23. Furthermore, decreased dietary phosphate in a vitamin D-depleted diet led to microarchitectural changes of trabecular and cortical bone, lower bone mass density, lower bone mass content and decreased bone strength, all indicating reduced bone quality. Taken together, our results show that osteomalacia can be induced in the adult female rat by depleting vitamin D and lowering phosphate content in the diet.

Fibroblast Growth Factor 23-Producing Phosphaturic Mesenchymal Tumor with Extraordinary Morphology Causing Oncogenic Osteomalacia

A possible cause of hypophosphatemia is paraneoplastic secretion of fibroblast growth factor 23 (FGF-23). Tumors secreting FGF-23 are rare, mostly of mesenchymal origin, usually benign, and may be located anywhere in the body, including hands and feet, which are often not represented in conventional imaging. A 50-year-old woman presented with diffuse musculoskeletal pain and several fractures. Secondary causes of osteoporosis were excluded. Laboratory analysis revealed hypophosphatemia and elevated alkaline phosphatase, parathyroid hormone, and FGF-23. Thus, oncogenic osteomalacia due to neoplastic FGF-23 secretion was suspected. FDG-PET-CT and DOTATATE-PET-CT imaging demonstrated no tumor. Cranial MRI revealed a tumorous mass in the left cellulae ethmoidales. The tumor was resected and histopathological examination showed a cell-rich tumor with round to ovoid nuclei, sparse cytoplasm, and sparse matrix, resembling an olfactory neuroblastoma. Immunohistochemical analysis first led to diagnosis of olfactory neuroblastoma, which was later revised to phosphaturic mesenchymal tumor. Following the resection, FGF-23 and phosphate levels normalized. In conclusion, we here describe a patient with an FGF-23-secreting phosphaturic mesenchymal tumor with an unusual morphology. Furthermore, we emphasize diagnostic pitfalls when dealing with FGF-23-induced hypophosphatemia.

The Association of Hypophosphatemia With Resistant Lactic Acidosis in Critical Care Illness

Critically ill patients are known to have a variety of electrolyte abnormalities. Lactic acidosis can frequently be seen secondary to shock states and is usually treated with aggressive volume resuscitation. Interestingly, hypophosphatemia is a potential cause of resistant lactic acidosis, which may not be as commonly identified or considered. We present a case of a 42-year-old man admitted twice over a span of 6 months with an elevated lactate level that did not resolve with volume resuscitation. It was ultimately determined that his lactic acidosis was due to hypophosphatemia after ruling out other potential causes. Phosphate replacement therapy resulted in the normalization of his lactate. In the literature, multiple theories have indicated the association of hypophosphatemia with lactic acidosis though no prior cases exist supporting a direct relationship. In this case, we set forth to evaluate the complicated relationship between all of these factors and to highlight the importance of early detection and treatment of hypophosphatemia, which may be beneficial in treating lactic acidosis.

Elevated FGF23 in a patient with hypophosphatemic osteomalacia associated with neurofibromatosis type 1

CONTEXT

The mechanism behind hypophosphatemia in the setting of neurofibromatosis type 1 (NF1) is not known. We describe a possible role of fibroblast growth factor-23 (FGF23) in the pathophysiology of hypophosphatemia in a patient with NF1.

CASE DESCRIPTION

A 34-year woman with NF1 presented with severe hypophosphatemia, osteomalacia, and elevated plasma FGF23. The patient had considerable improvement on replacement of oral phosphate. Two Ga68 DOTANOC PET-CT scans over a period of 2 years failed to detect any localized uptake. Immuno-staining for FGF23 was absent in the neural-derived tumour cells of the neurofibromas in the proband.

CONCLUSION

The patient with NF1 had elevated circulating FGF23. Tumour cells in the neurofibroma tissues did not stain for FGF23 on IHC. It is unlikely for neurofibromas to contribute to high circulating FGF23 levels in the proband.

Refeeding Syndrome

Refeeding syndrome describes the metabolic disturbances and clinical sequelae that occur in response to nutritional rehabilitation of patients who are moderate to severely malnourished. When risk factors are not identified and nutrition therapy is not managed appropriately, devastating consequences such as electrolyte depletion and imbalances, fluid overload, arrhythmia, seizure, encephalopathy, and death may occur. As this entity is often unrecognized, especially in pediatrics, becoming familiar with the pathophysiology, clinical manifestations, and management strategies will help clinicians caring for children avoid unnecessary morbidity and mortality. [Pediatr Ann. 2019;48(11):e448-e454.].

Reliability of calcium-phosphorus (Ca/P) ratio as a new, accurate and inexpensive tool in the diagnosis of some Ca-P disorders

PURPOSE

The serum calcium/phosphorus (Ca/P) ratio is an accurate tool to differentiate patients with primary hyperparathyroidism (PHPT) from healthy subjects. However, other disorders of the Ca-P metabolism might impair the Ca/P ratio, such as hypophosphatemia (HypoP) not PHPT related. The aim of this study is to examine the diagnostic value of Ca/P ratio in the diagnosis of PHPT and HypoP not PHPT related.

METHODS

Single-center, retrospective, case-control study, including 150 patients with PHPT and 306 patients with HypoP, compared with 150 controls. HypoP patients were enrolled among HIV-infected patients by selecting those with Fanconi-like syndrome due to antiretroviral treatment. Parameters which were measured were serum Ca, P, parathyroid hormone (PTH), 25-OH vitamin D, albumin and creatinine).

RESULTS

The Ca/P ratio was significantly higher in PHPT and HypoP patients, compared to controls (p < 0.0001). At receiver operator characteristic (ROC) curve analysis, the cut-off of 3.56 (2.75 SI) for Ca/P ratio was able to identify patients with PHPT and HypoP (sensitivity 95%; specificity 93%). Among patients with Ca/P ratio above 3.56, the thresholds of 10.3 mg/dL (2.6 mmol/L) for serum Ca (sensitivity 93%; specificity 98%) and 80.5 pg/mL for PTH (sensitivity 91%; specificity 91%) were defined for the specific diagnosis of PHPT.

CONCLUSIONS

The Ca/P ratio above 3.56 (2.75 SI) is a highly accurate tool to identify PHPT and HypoP not PHPT-related patients. Thanks to its simplicity, this index can be proposed as a screening and first-line examination in the diagnostic work-up when a disorder of Ca-P metabolism is suspected or should be ruled out.

Sinonasal hemangiopericytoma caused hypophosphatemic osteomalacia: A case report

RATIONALE

Tumor-induced osteomalacia (TIO) is a rare, paraneoplastic syndrome featured with fibroblast growth factor 23 (FGF23) secretion primarily by benign mesenchymal tumors and sometimes by malignancies. TIO diagnosis and treatment is often delayed because TIO usually has nonspecific generalized bone pain and weakness, and location of TIO tumor is quite challenging. Very few TIO caused by sinonasal hemangiopericytoma have been reported in the literature.

PATIENT CONCERNS

A 40-year-old Chinese woman presented with diffuse bone pain for more than 1 year. Laboratory examination showed hypophosphatemia, hyperphosphaturia, hypocalcemia, an elevated serum alkaline phosphatase (ALP) level and bone-specific ALP level. Imaging studies revealed low bone mineral density (BMD) and multiple pseudofractures at the ribs. F-18 fluorodeoxyglucose positron emission tomography was negative in searching for tumors. Because no tumor was located, the patient was treated with oral phosphate, calcium, and alfacalcidol, and achieved great relief in her symptoms and improvement in BMD. Six years later, the patient had breast cancer surgery and received chemotherapy, and still had hypophosphatemia. During this time, nasopharyngo-fiberscope showed nasal mass in her left nasal cavity. Then she had her nasal polyps removed and surprisingly the serum phosphate became normal.

DIAGNOSES AND INTERVENTIONS

The patient had the nasal mass resected, and pathological diagnosis of the nasal mass was sinonasal hemangiopericytoma. Immunohistochemical analysis was positive for FGF23. Thus the final diagnosis was osteomalacia induced by sinonasal hemangiopericytoma. Phosphate supplementation and alfacalcidol were discontinued.

OUTCOMES

The patient had normal serum phosphate after 6-month follow-up.

LESSONS

By presenting this case, we hope to remind clinicians that in patients with osteomalacia with undetermined reason and intranasal polypoid mass, sinonasal hemangiopericytoma should be suspected.

Legionella Pneumonia Complicated with Acquired Fanconi Syndrome

Legionella pneumonia is occasionally accompanied by renal complications; however, the cause of this remains unknown. We herein report a 70-year-old Japanese man with Legionella pneumonia who presented with hyponatremia, hypophosphatemia, and hypouricemia. The levels of urinary β2-microglobulin and N-acetyl-β-D-glucosaminidase were remarkably high, indicating severe renal tubular damage. The presence of glycosuria and aminoaciduria as well as increased fractional excretion of uric acid and decreased tubular reabsorption of phosphate indicated that the patient's condition was complicated with Fanconi syndrome. After antimicrobial therapy, the electrolyte abnormalities and renal tubular damage were completely resolved.

The Relationship between Hypomagnesemia and Pulmonary Function Tests in Patients with Chronic Asthma

OBJECTIVE

To investigate the relationship between serum values of magnesium and the parameters of the pulmonary function tests (PFT) in patients with chronic asthma.

SUBJECTS AND METHODS

This study recruited 50 patients with chronic stable asthma and 40 healthy individuals as a control group. Data on age, sex, severity of asthma, PFT, and details of drug therapy were obtained from each group. Serum magnesium, potassium, phosphorus, calcium, and sodium levels were also measured. To evaluate differences between groups, the Student t test or Mann-Whitney U test was performed for continuous variables, and the χ2 test for categorical variables.

RESULTS

In the asthma group, 10% (n = 9) of the patients had hypomagnesemia and 5.5% (n = 5) had hypophosphatemia. Patients with asthma were divided into two groups: the hypomagnesemic group (n = 9) and the normomagnesemic group (n = 41). Forced expiratory volume in 1 s (FEV1), FEV1%, peak expiratory flow (PEF), and PEF% were lower in the hypomagnesemic group than in the normomagnesemic group (p = 0.02). Multiple logistic regression analysis revealed a statistically significant association between hypomagnesemia and PFT in the hypomagnesemic asthmatic group. The correlations of age with FEV1, FEV1%, PEF, and PEF% were as follows: p = 0.00, r = 0.29; p = 0.00, r = 0.43; p = 0.03, r = 0.22; p = 0.00, r = 0.38; and p = 0.03, r = 0.22, respectively. The correlation of serum magnesium levels with PFT (FEV1, FEV1%, PEF, PEF%) were as follows: p = 0.001, r = 0.29; p = 0.001, r = 0.43; p = 0.03, r = 0.22; and p = 0.001, r = 0.38, respectively. The other electrolytes were within the normal range in both groups.

CONCLUSION

In this study, hypomagnesemia and hypophosphatemia were found to be the most common electrolyte abnormalities in patients with chronic stable asthma. FEV1, FEV1%, PEF, and PEF% were significantly lower in asthmatic patients with hypomagnesemia compared to asthmatic patients with normomagnesemia.

Bone Histology of Two Cases with Osteomalacia Related to Low-dose Adefovir

We performed a bone histomorphometric analysis in two patients demonstrating Fanconi syndrome with hypophosphatemia, adefovir-related bone disease and chronic hepatitis B infection. Both patients had osteomalacia, but showed two different histological patterns. The osteoid volume of the patient without risedronate increased with [(osteoid volume/ bone volume)×100=18.6%]. However, the osteoid volume of the patient receiving risedronate without vitamin D analogue showed a greater increase of 53.8%. In both patients bone pain and hypophosphatemia subsided soon after the discontinuation of adefovir and the administration of phosphate derivative. These findings show that bisphosphonate may worsen this disease when this drug is administered without a vitamin D analogue.

[Limited evidence for monitoring and treatment of hypophosphataemia in critically ill patients]

Hypophosphataemia is a potentially hazardous metabolic disturbance which is common in critically ill patients. The condition is reported to be associated with severe complications and increased mortality. It is unknown, whether hypophosphataemia has a causal effect or reflects the severity of illness. There are no randomized clinical trials to support treatment of hypophosphataemia with intravenous phosphate substitution, which has resulted in large variations in monitoring and treatment of hypophosphataemia in the intensive care unit.

A 'shocking' finish to the Dam tot Damloop event

A patient with status epilepticus after long-distance running is described. The patient, a young woman, was brought to our hospital with status epilepticus after completing in a running event, probably caused by an extremely low phosphate level of 0.30 mmol/l. Hypophosphataemia is a rare complication of running and can be caused by the use of phosphate in the glycogenolyticand glycolytic pathway.

Rhabdomyolysis Due to Severe Hypophosphatemia in Diabetic Ketoacidosis

Rhabdomyolysis is a syndrome characterized by injury to skeletal muscle fibers with disruption and release of toxic metabolites into circulation. It is characterized by triad of muscle weakness, myalgia and dark urine and is associated with increased creatine kinase and lactate dehydrogenase. A severely malnourished 10 year old girl with severe diabetic ketoacidosis as hemr initial presentation of type 1 diabetes mellitus developed rhabdomyolysis (CK- 12,000 U/L) with non-oliguric renal failure during her initial course of hospital stay. The possible cause of her RM was attributed to severe hypophosphatemia (minimum serum phosphate, 0.8 mg/dL). Management of diabetic ketoacidosis phosphate supplementation and urinary alkalinization with diuresis improved her clinical course. She was discharged on Day 9 with Insulin. We recommend frequent monitoring of serum phosphate during early period of DKA, particularly in malnourished children, and its normalization in case of severe hypophosphatemia.

[Management of hypophosphatemia: a case report]

Hypophosphatemia is defined by a serum phosphate level lower than 0.8 mmol/l. If hypophosphatemia is chronically maintained, it is associated with muscular, osteous, neurological or cardio-respiratory disorders. We describe a patient with isolated hypophosphatemia, detail the mechanisms of phosphate homeostasis, and envisage the differential diagnosis of hypophosphatemia. Furthermore, we propose a sequential decisional algorithm based on basic biological tests and few complementary investigations. Treatment options are reviewed.

[The clinical characteristics of 26 cases of hypophosphatemia osteomalacia misdiagnosed as spondyloarthritis]

OBJECTIVE

To study and summarize the clinical features of hypophosphatemia osteomalacia (HO) misdiagnosed as spondyloarthritis (SpA), aiming to analyze the reasons of misdiagnosis and improve the prognosis of such patients.

METHODS

A total of 26 cases of HO misdiagnosed as SpA were selected. Clinical features, laboratory tests, and image presentations were analyzed. Related literatures were reviewed.

RESULTS

(1) Clinical characters: 26 patients were included (12 males and 14 females) with a median age of 38 years (range 20-60). The mean disease duration was 3.2 years (range 0.75 to 10 years). Of all the patients, 15 were diagnosed as tumor-induced HO, 4 were long-term oral adefovir dipivoxil-related HO, 3 were associated with Fanconi syndrome, 2 were related to hyperparathyroidism, while 2 were Sjogren's syndrome complicated with renal tubular acidosis. All of the 26 patients presented with low back pain including 15 with night pain. The time of morning stiffness was about 30 minutes. Non-steroidal anti-inflammatory drugs were given to each patient whereas with poor efficacy, neither did other agents work well, such as glucocorticoids, disease modifying anti-rheumatic drugs and biologics. (2) LABORATORY FINDINGS: the platelet count and inflammatory markers such as erythrocyte sedimentation rate, C-reactive protein (CRP) were usually normal. The level of serum calcium was normal or slightly lower, nevertheless, all patients had hypophosphatemia and increased level of alkaline phosphatase (ALP). Patients with adefovir dipivoxil-related HO, Fanconi syndrome or Sjogren's syndrome complicated with renal tubular acidosis were characterized by hypokalemia, hyperchloremia and alkaline urine. Patients with hyperparathyroidism had elevated parathyroid hormone (PTH). Positive antinuclear antibodies (ANA) (titer ≥ 1: 320), anti-SSA/SSB antibodies were found in patients with Sjogren's syndrome. (3) Radiographic features: sacroiliac joint lesions were found in X-ray, CT, positron emission tomography (PET-CT) or MRI, however the lesions in sacrum or ilium were predominant rather than in joints. Abnormal bone imaging in ribs, long bones and soft tissues in addition to joints could be detected by bone scintigraphy.

CONCLUSION

HO is not uncommon in daily practice. Besides SpA, other diseases should be considered in the setting of low-back pain and diseased sacroiliac joints. Comprehensive screening of bone metabolic parameters contributes to the timely diagnosis of HO.

Hypophosphatemic osteomalacia and bone sclerosis caused by a novel homozygous mutation of the FAM20C gene in an elderly man with a mild variant of Raine syndrome

BACKGROUND

Hypophosphatemia and increased serum fibroblast growth factor 23 (FGF23) levels have been reported in young brothers with compound heterozygous mutations for the FAM20C gene; however, rickets was not observed in these cases. We report an adult case of Raine syndrome accompanying hypophosphatemic osteomalacia with a homozygous FAM20C mutation (R408W) associated with increased periosteal bone formation in the long bones and an increase in bone mineral density in the femoral neck.

CASE

The patient, a 61-year-old man, was born from a cousin-to-cousin marriage. A short stature and severe dental demineralization were reported at an elementary school age. Hypophosphatemia was noted inadvertently at 27years old, at which time he started to take an active vitamin D metabolite (alphacalcidol) and phosphate. He also manifested ossification of the posterior longitudinal ligament. On bone biopsy performed at the age of 41years, we found severe osteomalacia surrounding osteocytes, which appeared to be an advanced form of periosteocytic hypomineralized lesions compared to those reported in patients with X-linked hypophosphatemic rickets. Laboratory data at 61years of age revealed markedly increased serum intact-FGF23 levels, which were likely to be the cause of hypophosphatemia and the decreased level of 1,25(OH)2D. We recently identified a homozygous FAM20C mutation, which was R408W, in this patient. When expressed in HEK293 cells, the R408W mutant protein exhibited impaired kinase activity and secretion.

DISCUSSION

Our findings suggest that certain homozygous FAM20C mutations can cause FGF23-related hypophosphatemic osteomalacia and indicate the multiple roles of FAM20C in bone.

Fibroblast growth factor 23 is elevated in tenofovir-related hypophosphatemia

In human immunodeficiency virus (HIV)-infected patients, tenofovir disoproxil fumarate (TDF) may cause hypophosphatemia leading to osteomalacia due to renal phosphate wasting. Fibroblast growth factor 23 (FGF23) may play a role in this setting. We present an HIV-infected patient with TDF-induced profound hypophosphatemia, Fanconi syndrome, osteomalacia, and bilateral hip fracture. Routine serum biochemistry was assessed by standard methods. The plasma FGF23 concentration was measured at Mayo Laboratories (Scottsdale, AZ, USA). Bone mineral density (BMD) was measured using a Hologic Discovery densitometer. At presentation, the patient's plasma C-terminal FGF23 was 2,760 reference units (RU)/mL (15 times upper limit of normal; reference interval [RI] ≤ 180 RU/mL), serum phosphate was 0.58 (RI 0.8-1.6 mmol/L), and TmPO4/GFR was 95%. DXA at the lumbar spine showed a Z score of -4.0. Vitamin D3 and oral phosphate were administered, and TDF was discontinued. After 4 months off TDF, lumbar spine BMD significantly increased by 12% (Z score -3.5); by 6 months the plasma C-terminal FGF23 declined to 1.8 times the upper limit of normal, and both urine and serum phosphate levels normalized. By its marked elevation and subsequent near normalization, FGF23 may be responsible for a component of the phosphate wasting syndrome in these patients. The time course of resolution was 6 months. As expected, with calcium, vitamin D, and phosphate management, BMD significantly improved with resolution of osteomalacia. Clinicians should be aware of this side effect of TDF and the time course of its resolution.

Rickets

Rickets, historically referred to as "the English disease", is common worldwide. Absence of phosphate at the growth plate and mineralising bone surfaces due to inadequate vitamin D supply either from sunlight exposure or diet is the main cause. Inherited disorders causing hypophosphataemia have shown the intricacies of phosphate metabolism. Present advice about the provision of vitamin D to young infants needs to be clarified; the existing guidance is fragmentary and contradictory, and will not help to eradicate the disease.

Postzygotic HRAS mutation causing both keratinocytic epidermal nevus and thymoma and associated with bone dysplasia and hypophosphatemia due to elevated FGF23

INTRODUCTION

Epidermal nevus syndrome is a rare group of disorders characterized by the combination of congenital epidermal nevi and extracutaneous features, including skeletal, neurological, ocular, and other systemic findings. We report a case of keratinocytic epidermal nevus syndrome that includes a thymoma, bone dysplasia, and hypophosphatemia with elevated fibroblast growth factor 23 (FGF23) levels associated with postzygotic HRAS mutation.

CASE REPORT

A 14-year-old boy was admitted due to recent limping. The physical examination revealed multiple right-sided linear epidermal nevi along Blaschko's lines. Magnetic resonance imaging showed cystic lesions in cervical bones and thymoma, and x-ray examination showed cystic lesions in the hands. Biochemical studies demonstrated severe hypophosphatemia, normocalcemia, high normal PTH, low 25-hydroxyvitamin D and low 1,25-dihydroxyvitamin D levels. The serum FGF23 C-terminal level was normal, but the intact FGF23 level was found to be elevated. Genetic evaluation revealed a heterozygote mutation in the HRAS gene in both the keratinocytic epidermal nevus and thymoma but not in DNA extracted from blood lymphocytes, thus establishing the mutation as postzygotic.

DISCUSSION

Postzygotic mutations in HRAS lead to elevation of FGF23 levels, as found in mutated PHEX, FGF23, DMP1, and ENPP1 genes, which lead to hypophosphatemia.

CONCLUSION

An identical postzygotic HRAS mutation was shown to be present in both keratinocytic epidermal nevus and thymoma and to be associated with bone lesions and hypophosphatemia due to elevated FGF23 levels. These may all be related to the HRAS mutation.

Severe hypophosphataemia after intravenous iron administration

Currently, in many centres, intravenous administration of iron is becoming increasingly popular because of higher efficacy and decreased side effects, mainly gastrointestinal, compared with oral iron therapy. Studies of intravenous ferric carboxymaltose administration in the postpartum setting and in patients with non-dialysis-dependent chronic kidney disease revealed a decrease in serum phosphate levels that was generally asymptomatic and transient. Here, we report four cases of severe and symptomatic hypophosphataemia after intravenous iron administration. All patients received this as therapy for iron deficiency anaemia due to heavy menstrual bleeding. In most cases, a pre-existent disorder in the phosphate homeostasis existed, such as a secondary (cases 3 and 4) or tertiary hyperparathyroidism (case 1). However, in the second case there were no risk factors for a dysregulation of the phosphate homeostasis. Based on these findings, we conclude that severe and symptomatic hypophosphatemia can occur as a side effect of intravenous iron administration and can persist for months after administration. Especially patients with low phosphate levels prior to therapy due to concomitant disorders in phosphate homeostasis (e.g. hyperparathyroidism, vitamin D deficiency) are at risk.

Prolonged disturbance of consciousness caused by severe hypophosphatemia: a report of two cases

We herein describe two patients with a prolonged disturbance of consciousness due to severe hypophosphatemia. Case one presented with pneumococcal infection and acute exacerbation of chronic obstructive pulmonary disease and asthma. Case two presented with diabetic foot infections and diabetic ketoacidosis. Both patients responded to initial therapy for their primary diseases, but consciousness became worse in both cases. Their test results for impaired consciousness revealed severe hypophosphatemia; therefore, phosphate replacement therapy was administered, thus resulting in complete alertness. These cases demonstrate that we should consider the possibility of hypophosphatemia in critically ill patients with an altered consciousness.

Refeeding hypophosphatemia in adolescents with anorexia nervosa: a systematic review

The rate of adolescents presenting with anorexia nervosa (AN) is increasing. Medically unstable adolescents are admitted to the hospital for nutrition restoration. A lack of global consensus on appropriate refeeding practices of malnourished patients has resulted in inconsistent refeeding practices. Refeeding hypophosphatemia (RH) is the most common complication associated with refeeding the malnourished patient. This review sought to identify the range of refeeding rates adopted globally and the implication that total energy intake and malnutrition may have on RH while refeeding adolescents with anorexia nervosa. Studies were identified by a systematic electronic search of medical databases from 1980 to September 2012. Seventeen publications were identified, including 6 chart reviews, 1 observational study, and 10 case reports, with a total of 1039 subjects. The average refeeding energy intake was 1186 kcal/d, ranging from 125-1900 kcal/d, with a mean percentage median body mass index (% mBMI) of 78%. The average incidence rate of RH was 14%. A significant correlation between malnutrition (% mBMI) and post-refeeding phosphate was identified (R (2) = 0.6, P = .01). This review highlights the disparity in refeeding rates adopted internationally in treating malnourished adolescents with anorexia nervosa. Based on this review, the severity of malnutrition seems to be a marker for the development of RH more so than total energy intake.