Genetic epidemiological analysis of hypouricaemia from 4993 Japanese on non-functional variants of URAT1/SLC22A12 gene.

OBJECTIVES: Up to 0.3% of Japanese have hypouricaemia. Most cases appear to result from a hereditary disease, renal hypouricaemia (RHUC), which causes exercise-induced acute kidney injury and urolithiasis. However, to what extent RHUC accounts for hypouricaemia is not known. We therefore investigated its frequency and evaluated its risks by genotyping a general Japanese population. METHODS: A cohort of 4993 Japanese was examined by genotyping the non-functional variants R90H (rs121907896) and W258X (rs121907892) of URAT1/SLC22A12, the two most common causative variants of RHUC in Japanese. RESULTS: Participants' fractional excretion of uric acid and risk allele frequencies markedly increased at lower serum uric acid (SUA) levels. Ten participants (0.200%) had an SUA level ≤2.0 mg/dl and nine had R90H or W258X and were likely to have RHUC. Logistic regression analysis revealed these URAT1 variants to be significantly and independently associated with the risk of hypouricaemia and mild hypouricaemia (SUA ≤3.0 mg/dl) as well as sex, age and BMI, but these URAT1 variants were the only risks in the hypouricaemia population (SUA ≤2.0 mg/dl). W258X was only a risk in males with SUA ≤3.0 mg/dl. CONCLUSION: Our study accurately reveals the prevalence of RHUC and provides genetic evidence for its definition (SUA ≤2.0 mg/dl). We also show that individuals with SUA ≤3.0 mg/dl, especially males, are prone to RHUC. Our findings will help to promote a better epidemiological understanding of RHUC as well as more accurate diagnosis, especially in males with mild hypouricaemia.

Proteinuria-associated renal magnesium wasting leads to hypomagnesemia: a common electrolyte abnormality in chronic kidney disease.

BACKGROUND: Hypomagnesemia (Hypo-Mg) predicts mortality and chronic kidney disease (CKD) progression. However, in CKD, its prevalence, kidney-intrinsic risk factors, and the effectiveness of oral magnesium (Mg) therapy on serum Mg levels is uncertain. METHODS: In a cross-sectional study enrolling pre-dialysis outpatients with CKD, the prevalence of electrolyte abnormalities (Mg, sodium, potassium, calcium and phosphorus) was compared. In an open-label randomized controlled trial (RCT), we randomly assigned CKD patients to either the magnesium oxide (MgO) or control arm. The outcome was serum Mg levels at 1 year. RESULTS: In 5126 patients, Hypo-Mg was the most common electrolyte abnormality (14.7%) with similar prevalence across stages of CKD. Positive proteinuria was a risk factor of Hypo-Mg (odds ratio 2.2; 95% confidence interval 1.2-4.0). However, stratifying the analyses by diabetes mellitus (DM), it was not significant in DM (Pinteraction = 0.04). We enrolled 114 patients in the RCT. Baseline analyses showed that higher proteinuria was associated with higher fractional excretion of Mg. This relationship between proteinuria and renal Mg wasting was mediated by urinary tubular markers in mediation analyses. In the MgO arm, higher proteinuria or tubular markers predicted a significantly lower 1-year increase in serum Mg. In patients with a urinary protein-to-creatinine ratio (uPCR) <0.3 g/gCre, serum Mg at 1 year was 2.4 and 2.0 mg/dL in the MgO and control arms, respectively (P < 0.001), with no significant between-group difference in patients whose uPCR was ≥0.3 g/gCre (Pinteraction=0.001). CONCLUSIONS: Proteinuria leads to renal Mg wasting through tubular injuries, which explains the high prevalence of Hypo-Mg in CKD.

Distribution and Characteristics of Hypouricemia within the Japanese General Population: A Cross-Sectional Study.

Background and objectives: There is insufficient epidemiological knowledge of hypouricemia. In this study, we aimed to describe the distribution and characteristics of Japanese subjects with hypouricemia. Materials and Methods: Data from subjects who underwent routine health checkups from January 2001 to December 2015 were analyzed in this cross-sectional study. A total of 246,923 individuals, which included 111,117 men and 135,806 women, met the study criteria. The participants were divided into quartiles according to their serum uric acid (SUA) levels. We subdivided the subjects with hypouricemia, which was defined as SUA level ≤ 2.0 mg/dL, into two groups and compared their characteristics, including their cardiovascular risks. Results: The hypouricemia rates were 0.46% overall, 0.21% for the men and 0.66% for the women (P < 0.001). The number of the subjects with hypouricemia showed two distributions at SUA levels of 0.4⁻1.1 mg/dL (lower hypouricemia group), which included a peak at 0.7⁻0.8 mg/dL, and at SUA levels of 1.4⁻2.0 mg/dL (higher hypouricemia group). The men in the higher hypouricemia group had lower body mass indexes (BMI) and triglyceride (TG) levels and had higher fasting blood glucose levels than those in the lower hypouricemia group. The women in the higher hypouricemia group were younger; had lower BMI, total protein, TG, total cholesterol and low-density lipoprotein cholesterol levels; and had higher estimated glomerular filtration rates levels compared to those in the lower hypouricemia group. Conclusions: The characteristics of the individuals in the lower and higher hypouricemia groups differed significantly, indicating different pathophysiologies within each group.

Posterior reversible encephalopathy syndrome (PRES) and hypomagnesemia: A frequent association?

Posterior reversible encephalopathy syndrome (PRES) is a serious neurological condition encountered in various medical fields. Pathophysiological factor(s) common to PRES cases of apparently unrelated etiologies are yet to be found. Based on the hypothesis that hypomagnesemia might participate in the cascade leading to PRES, our study sought to verify whether hypomagnesemia is frequently associated with PRES regardless of etiology. From a retrospective study of a cohort of 57 patients presenting with PRES of different etiologies, presented here are the findings of 19 patients with available serum magnesium levels (SMLs) during PRES. In the acute phase of PRES, hypomagnesemia was present in all 19 patients in spite of differences in etiology (including immunosuppressive drugs, hypertensive encephalopathy, eclampsia, systemic lupus erythematosus, iatrogenic etiology and unknown). SMLs were within normal ranges prior to PRES and below normal ranges during the first 48h of PRES, with a significant decrease in SMLs during the acute phase. In this retrospective study, constant hypomagnesemia was observed during the acute phase of PRES regardless of its etiology. These results now require larger studies to assess the particular importance of acute hypomagnesemia in PRES and especially the possible need to treat PRES with magnesium sulfate.

Association between hypouricemia and reduced kidney function: a cross-sectional population-based study in Japan.

BACKGROUND: Hypouricemia, conventionally defined as a serum uric acid level of ≤2 mg/dl, is considered a biochemical disorder with no clinical significance. However, individuals with renal hypouricemia have a high risk of urolithiasis and exercise-induced acute kidney injury, both of which are risk factors for reduced kidney function. METHODS: To test the hypothesis that individuals with hypouricemia would be at a higher risk of reduced kidney function, we conducted a population-based cross-sectional study using data from the Specific Health Checkups and Guidance System in Japan. Logistic analysis was used to examine the relationship between hypouricemia and reduced kidney function, defined as estimated glomerular filtration rate <60 ml/min/1.73 m(2). RESULTS: Among 90,710 men (mean age, 63.8 years) and 136,935 women (63.7 years), 193 (0.2%) and 540 (0.4%) were identified as having hypouricemia, respectively. The prevalence of hypouricemia decreased with age in women (p for trend <0.001), but not in men (p for trend = 0.24). Hypouricemia was associated with reduced kidney function in men (odds ratio, 1.83; 95% confidence interval, 1.23-2.74), but not in women (0.61; 0.43-0.86), relative to the reference category (i.e., serum uric acid levels of 4.1-5.0 mg/dl) after adjusting for age, drinking, smoking, diabetes, hypertension, hypercholesterolemia, obesity, and history of renal failure. Sensitivity analyses stratified by diabetic status yielded similar results. CONCLUSIONS: This study is the first to provide evidence that hypouricemia is associated with reduced kidney function in men. Further research will be needed to determine the long-term prognosis of individuals with hypouricemia.

Retrospective cohort study of familial hypomagnesaemia with hypercalciuria and nephrocalcinosis due to CLDN16 mutations.

BACKGROUND: Familial hypomagnesaemia with hypercalciuria and nephrocalcinosis (FHHNC) is a rare autosomal recessive tubular disorder exhibiting a high risk for progressive chronic kidney disease (CKD). METHODS: This is a retrospective multicentre study of 25 paediatric cases with FHHNC in Poland. Median age at diagnosis was 4 years and median follow-up time was 4.8 years. RESULTS: All cases of FHHNC carried recessive mutations in CLDN16. The founder mutation in CLDN16, Leu151Phe, was the most frequent cause of FHHNC in Polish patients, with 13 (52%) cases being homozygous and 5 (20%) carrying Leu151Phe allele in compound heterozygosity. All cases showed nephrocalcinosis, increased urinary fractional excretion of magnesium and hypercalciuria. Other disease features included hypomagnesaemia (76%), hyperparathyroidism (76%), hyperuricaemia (56%) and hypocitraturia (60%). Treatment with thiazides effectively reduced hypercalciuria in most cases. During follow-up, renal function declined in 60% of patients; 12% of patients reached CKD stage 3 or 4 and one patient developed end-stage renal failure. CONCLUSIONS: We report one of the largest cohorts of FHHNC cases caused by CLDN16 mutations. A missense variant of CLDN16, Leu151Phe, is the most common mutation responsible for FHHNC in Poland. Additionally, we found that normomagnesaemia does not exclude FHHNC and the calculation of fractional excretion of Mg can be diagnostic in the setting of normomagnesaemia. We also demonstrate the efficacy of a treatment with thiazides in terms of hypercalciuria in the majority of patients.

Proton pump inhibitors and hospitalization with hypomagnesemia: a population-based case-control study.

BACKGROUND: Some evidence suggests that proton pump inhibitors (PPIs) are an under-appreciated risk factor for hypomagnesemia. Whether hospitalization with hypomagnesemia is associated with use of PPIs is unknown. METHODS AND FINDINGS: We conducted a population-based case-control study of multiple health care databases in Ontario, Canada, from April 2002 to March 2012. Patients who were enrolled as cases were Ontarians aged 66 years or older hospitalized with hypomagnesemia. For each individual enrolled as a case, we identified up to four individuals as controls matched on age, sex, kidney disease, and use of various diuretic classes. Exposure to PPIs was categorized according to the most proximate prescription prior to the index date as current (within 90 days), recent (within 91 to 180 days), or remote (within 181 to 365 days). We used conditional logistic regression to estimate the odds ratio for the association of outpatient PPI use and hospitalization with hypomagnesemia. To test the specificity of our findings we examined use of histamine H2 receptor antagonists, drugs with no causal link to hypomagnesemia. We studied 366 patients hospitalized with hypomagnesemia and 1,464 matched controls. Current PPI use was associated with a 43% increased risk of hypomagnesemia (adjusted odds ratio, 1.43; 95% CI 1.06-1.93). In a stratified analysis, the risk was particularly increased among patients receiving diuretics, (adjusted odds ratio, 1.73; 95% CI 1.11-2.70) and not significant among patients not receiving diuretics (adjusted odds ratio, 1.25; 95% CI 0.81-1.91). We estimate that one excess hospitalization with hypomagnesemia will occur among 76,591 outpatients treated with a PPI for 90 days. Hospitalization with hypomagnesemia was not associated with the use of histamine H2 receptor antagonists (adjusted odds ratio 1.06; 95% CI 0.54-2.06). Limitations of this study include a lack of access to serum magnesium levels, uncertainty regarding diagnostic coding of hypomagnesemia, and generalizability of our findings to younger patients. CONCLUSIONS: PPIs are associated with a small increased risk of hospitalization with hypomagnesemia among patients also receiving diuretics. Physicians should be aware of this association, particularly for patients with hypomagnesemia. Please see later in the article for the Editors' Summary.

Prevalence of kidney failure in adults diagnosed with hereditary tubulopathies.

BACKGROUND: Inherited tubulopathies are rare kidney diseases with few data available in the literature regarding their long-term renal prognosis. This study aimed to evaluate the prevalence of kidney failure in adults with confirmed genetic tubulopathy and to describe the corresponding clinical and genetic findings. METHODS: In this observational cohort study, we focused on genetic tubulopathies assumed to impact kidney function. In all adult patients genetically diagnosed in our laboratory between 2001 and 2019, we estimated Glomerular Filtration Rate (eGFR) at diagnosis using the Modification of diet in renal disease (MDRD) formula. Kidney failure was defined as an eGFR < 60 ml/min/1.73 m2. RESULTS: A total of 2145 patients underwent genetic testing, confirming a genetic tubulopathy in 1031 cases (48%). We identified 116 patients out of 885 with available data with kidney failure, mostly diagnosed with Dent disease and distal renal tubular acidosis (respectively, 31% and 20%), followed by familial hypomagnesemia with hypercalciuria and nephrocalcinosis and renal hypophosphatemia/infantile hypercalcemia. Renal prognosis appeared particularly impacted in familial hypomagnesemia with hypercalciuria and nephrocalcinosis and Dent disease, while preserved in Gitelman syndrome. CONCLUSION: In this cohort, 13% of adults with genetic tubulopathy had kidney failure at diagnosis, with this rate varying greatly according to tubulopathies and suggesting a significant impact on renal prognosis. Even in adults, genetic analyses yield a good diagnostic rate in selected patients, and should be performed as soon as possible, in order to improve the renal management of patients and their relatives.

Out-of-hospital use of proton pump inhibitors and hypomagnesemia at hospital admission: a nested case-control study.

BACKGROUND: Case series suggest that long-term use of proton pump inhibitors (PPIs) is associated with hypomagnesemia, but the current literature lacks systematically collected data. Our aim was to examine whether hypomagnesemia at the time of hospital admission is associated with out-of-hospital use of PPIs. STUDY DESIGN: Nested case-control study matched for age and sex. SETTING & PARTICIPANTS: Data were collected retrospectively from a tertiary acute-care facility. Eligible cases consisted of 402 adults with hypomagnesemia (serum magnesium <1.4 mEq/L) at the time of hospital admission to medical services, age- and sex-matched with 402 control individuals with normal serum magnesium levels (1.4-2.0 mEq/L). PREDICTOR: Out-of-hospital PPI use was identified in the hospital record. An omeprazole equivalent dose was calculated when possible. Covariates included the Charlson-Deyo comorbidity index, diabetes, diuretic use, estimated glomerular filtration rate, and gastroesophageal reflux. OUTCOME: Multivariable conditional logistic regression analyses were used to examine the association of PPI use with hypomagnesemia at the time of hospital admission. RESULTS: PPI use was not associated with hypomagnesemia (adjusted OR, 0.82; 95% CI, 0.61-1.11). Neither PPI type nor omeprazole equivalent daily dose was associated with hypomagnesemia. Sensitivity analyses of PPI use restricted to patients with esophageal disorders (adjusted OR, 1.00; 95% CI, 0.69-1.45), severe hypomagnesemia (magnesium, ≤1.0 mEq/L; adjusted OR, 0.78; 95% CI, 0.13-4.61), or estimated glomerular filtration rate ≥60 mL/min/1.73 m(2) (adjusted OR, 0.84; 95% CI, 0.53-1.34) were unrevealing. LIMITATIONS: Exposure misclassification; hospitalized patients on medical services may not be representative of a broader ambulatory-based population. CONCLUSIONS: In a hospital-based adult population, out-of-hospital PPI use is not associated with hypomagnesemia at the time of hospital admission to medical services. In light of these inconclusive results, prospective cohort studies are needed to address this rare potential medication-related adverse effect.

Hereditary causes of kidney stones and chronic kidney disease.

Adenine phosphoribosyltransferase (APRT) deficiency, cystinuria, Dent disease, familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC), and primary hyperoxaluria (PH) are rare but important causes of severe kidney stone disease and/or chronic kidney disease in children. Recurrent kidney stone disease and nephrocalcinosis, particularly in pre-pubertal children, should alert the physician to the possibility of an inborn error of metabolism as the underlying cause. Unfortunately, the lack of recognition and knowledge of the five disorders has frequently resulted in an unacceptable delay in diagnosis and treatment, sometimes with grave consequences. A high index of suspicion coupled with early diagnosis may reduce or even prevent the serious long-term complications of these diseases. In this paper, we review the epidemiology, clinical features, diagnosis, treatment, and outcome of patients with APRT deficiency, cystinuria, Dent disease, FHHNC, and PH, with an emphasis on childhood manifestations.

Clinical and molecular characterization of Turkish patients with familial hypomagnesaemia: novel mutations in TRPM6 and CLDN16 genes.

BACKGROUND: Recent identification and characterization of novel renal Mg(2+) transporters and ion channels have greatly increased our understanding of the normal physiology of renal magnesium handling. METHODS: The present study deals with the clinical and molecular characterization of eight Turkish children (median age 10.6 years, range 3-16.2 years, five boys and three girls) with primary hypomagnesaemia from six families. RESULTS: All patients initially presented with tetany and convulsions. Laboratory evaluation yielded severely low serum magnesium levels and low serum calcium levels in all patients. While six patients exhibited inadequately low parathyroid hormone levels, the two remaining patients showed hyperparathyroidism, hypercalciuria and nephrocalcinosis. Genetic studies revealed familial hypomagnesaemia with secondary hypocalcaemia (HSH) due to a TRPM6 mutation in six patients and familial hypomagnesaemia with hypercalciuria and nephrocalcinosis (FHHNC) due to a CLDN16 mutation in one patient. CONCLUSIONS: Among recently identified magnesium-wasting disorders, HSH and FHHNC represent two major entities also in the Turkish population. Besides clinical course and laboratory diagnosis of hypomagnesaemia, the detection of renal calcium wasting and parathyroid function are crucial to differentiate between these most prevalent forms of hereditary magnesium deficiency. While TRPM6 mutations underlying HSH almost uniformly lead to a complete loss of function of the TRPM6 protein, the severity of FHHNC phenotype depends on the residual function of the mutated claudin-16 protein.

Pediatric reference values for serum magnesium levels in Iranian subjects.

Magnesium (Mg), an essential element, plays important roles in many physiological functions. Mg deficiency is associated with insulin resistance, cardiovascular disease, and disorders of the nervous system. The aim of this study was to determine reference values for serum Mg concentration in pediatrics. Serum Mg level was measured by flame atomic absorption spectrophotometry in 306 subjects (141 boys and 165 girls), aged 3-19 years, selected from among participants of the Tehran Lipid and Glucose Study. The International Federation of Clinical Chemistry guidelines (IFCC) and the robust method were used for determining reference values for sample sizes greater or less than 120 subjects respectively. The 95% reference values for serum Mg concentrations were 0.76-1.0, 0.75-1.0, and 0.76-0.99 mmol/L in boys, girls, and the all subjects respectively. According to the reference values obtained in this study, the prevalences of hypo- and hypermagnesemia, were 5.9% and 5.6% respectively. In conclusion, the current study presents pediatric reference values for serum Mg levels derived from a randomly selected healthy population, values which could be instrumental in detecting serum Mg abnormalities.

Hypomagnesaemia is absent in children with autosomal dominant polycystic kidney disease.

BACKGROUND: Hypomagnesaemia is present in 40-50% of children with autosomal dominant renal cysts and diabetes syndrome (RCAD). On the contrary, the prevalence of hypomagnesaemia in children with autosomal dominant polycystic kidney disease (ADPKD) has never been examined. We aimed to investigate whether hypomagnesaemia is present in children with polycystic kidney diseases. METHODS: Children with cystic kidney diseases were investigated in a cross-sectional study. Serum concentrations of magnesium (S-Mg) and fractional excretion of magnesium (FE-Mg) were tested. Fifty-four children with ADPKD ( n = 26), autosomal recessive polycystic kidney disease (ARPKD) ( n = 16) and RCAD ( n = 12) with median age of 11.2 (0.6-18.6) years were investigated. RESULTS: Hypomagnesaemia (S-Mg < 0.7 mmol/L) was detected in none of the children with ADPKD/ARPKD and in eight children (67%) with RCAD. Median S-Mg in children with ADPKD/ARPKD was significantly higher than in children with RCAD (0.89 vs. 0.65 mmol/L, P < 0.01). The FE-Mg was increased in 23% of patients with ADPKD/ARPKD (all had chronic kidney disease stages 2-4) and in 63% of patients with RCAD, where it significantly correlated with estimated glomerular filtration rate (r = -0.87, P < 0.01). CONCLUSIONS: Hypomagnesaemia is absent in children with ADPKD or ARPKD and could serve as a marker for differential diagnostics between ADPKD, ARPKD and RCAD in children with cystic kidney diseases of unknown origin where molecular genetic testing is lacking. However, while hypomagnesaemia, in the absence of diuretics, appears to rule out ADPKD and ARPKD, normomagnesaemia does not rule out RCAD at least in those aged <3 years.

Hypomagnesemia During Teriparatide Treatment in Osteoporosis: Incidence and Determinants.

In our clinical experience, we have encountered patients who developed hypomagnesemia after the introduction of teriparatide. Some trials have reported hypomagnesemia as an adverse event during teriparatide treatment, but this issue had never been studied specifically. Our objective was twofold: 1) determine the incidence of hypomagnesemia (serum magnesium <0.7 mmol/L) associated with teriparatide in a retrospective cohort and 2) identify the predisposing factors to hypomagnesemia in this cohort. We reviewed the files of 53 patients treated for severe osteoporosis with teriparatide for 6 to 24 months between May 2008 and January 2016. Serum magnesium levels were measured at 0, 3, 6, 12, 18, and 24 months. In the full cohort, we observed an average decrease of serum magnesium of 0.075 mmol/L, 0.069 mmol/L, 0.085 mmol/L, 0.086 mmol/L (p < 0.001) at 3, 6, 12 months, and at the end of the treatment, respectively. The cumulative incidence of hypomagnesemia during treatment with teriparatide was 35.9% (19 patients). Patients' older age (71.1 versus 65.1 years; p = 0.05) and lower baseline level of magnesium before teriparatide treatment (0.81 mmol/L versus 0.85 mmol/L; p = 0.03) were significant risk factors for teriparatide-induced hypomagnesemia. The average decrease of serum magnesium was greater in the patients who developed hypomagnesemia compared with normomagnesemic patients at 3 months (0.110 mmol/L versus 0.054 mmol/L; p = 0.02), 6 months (0.139 mmol/L versus 0.036 mmol/L; p < 0.001), and 12 months (0.156 mmol/L versus 0.048 mmol/L; p < 0.001). Serum calcium, creatinine, and parathyroid hormone remained normal throughout the treatment period. We observed a statistically significant decrease in the serum magnesium levels in patients treated with teriparatide for severe osteoporosis. Older age and lower baseline magnesium were significant determinants of hypomagnesemia. Closer monitoring of serum magnesium level should be considered in these patients. © 2018 American Society for Bone and Mineral Research.

Mineral Disorders in Adult Inpatients Receiving Parenteral Nutrition. Is Older Age a Contributory Factor?

BACKGROUND: Parenteral nutrition (PN)-dependent adults and elderly individuals who are admitted to hospital treatment are potentially susceptible to mineral disorder complications due to depleted physiological reserves, loss of lean body mass, and increased fat mass, thus worsening inflammation. AIM: The purpose of this study is to evaluate the prevalence of hypophosphatemia, hypokalemia, and hypomagnesaemia prior and within the first 7 days of PN infusion. Furthermore, whether malnutrition and old age are associated with these disorders was also investigated. METHODS: This study included a historical cohort of adult patients, and 1,040 patients whose information was prospectively entered in the database were evaluated. RESULTS: Of the 781 patients, 27.3% were ≥65 years, 80.9% had undergone surgical treatment, 74.3% were in the intensive care unit, and 17.9% died during the hospitalization period. About 17.1% patients were malnourished. Protein energy malnutrition (PEM) was observed in 31.9% of the elderly patients and 27.1% of adults in general. Hypophosphatemia, hypokalemia, and hypomagnesemia were more prevalent before the start of PN infusion (D0: 214 [18.4%]), and new events were more common during the first 2 days of PN infusion (D1: 283 [23.1%]; D2: 243 [20.1%]. Elderly patients were more susceptible to developing hypophosphatemia (odds ratio [OR]: 1.69; 95% confidence interval [CI]: 1.29-2.19; p<0.001). Patients with PEM were also more susceptible to hypophosphatemia (OR: 3.75; 95% CI: 1.13-12.47; p=0.036). CONCLUSION: Hypophosphatemia, hypokalemia, and hypomagnesemia were frequently observed in hospitalized adults and elderly patients before and particularly during the first 2 days of PN infusion. Elderly patients and patients with PEM are more susceptible to developing hypophosphatemia.

Extreme hypomagnesemia: characteristics of 119 consecutive inpatients.

Extreme hypomagnesemia (hypoMg) can be encountered in many situations, but little data currently exist. Our aim is to describe the epidemiological, clinical, etiological characteristics, and the biological abnormalities of consecutive inpatients with extreme hypomagnesemia. In our observational monocentric study, between 1st July 2000 and April 2015, all inpatients with extreme hypomagnesemia, defined by at least one plasma magnesium concentration (PMg) below 0.3 mmol/L, were included. Demographic, clinical, biological characteristics and the drugs prescribed before the qualifying PMg measurement were retrospectively collected. 41,069 patients had at least one PMg assessment. The prevalence of extreme hypomagnesemia is 0.3% (119 inpatients). The median age is 70 years, 52% are women. The patients were mainly hospitalized in intensive care (n = 37, 31.1%), oncology (n = 21, 17.6%), gastroenterology (n = 18, 15.1%) and internal medicine (n = 16, 13.4%) departments. One hundred patients (84%) had a medical history of gastrointestinal disease (39% with bowel resections, 24% with stoma), and 50 (42%) had a cancer history. The drugs most commonly prescribed (known to induce hypoMg) are proton pump inhibitors (PPI) (n = 77, 70%), immunosuppressive regimens (n = 25, 22.5%), platinum salt-based chemotherapies (n = 19, 17.1%), and diuretics (n = 22, 19.8%). The suspected causes of hypomagnesemia are often multiple, but drugs (46%, including PPI in 19%) and chronic gastrointestinal disorders (37%) are prominent. Associated electrolyte disturbances include hypocalcemia (77%) and mild hypokalemia (51%). The 1-month mortality from all causes is 16%. Extreme hypomagnesemia is rare in inpatients, and is frequently associated with severe hypocalcemia. Digestive disorders and drugs are the main contributory causes.

Hereditary xanthinuria is not so rare disorder of purine metabolism.

Hereditary xanthinuria (type I) is caused by an inherited deficiency of the xanthine oxidorectase (XDH/XO), and is characterized by very low concentration of uric acid in blood and urine and high concentration of urinary xanthine, leading to urolithiasis. Type II results from a combined deficiency of XDH/XO and aldehyde oxidase. Patients present with hematuria, renal colic, urolithiasis or even acute renal failure. Clinical symptoms are the same for both types. In a third type, clinically distinct, sulfite oxidase activity is missing as well as XDH/XO and aldehyde oxidase. The prevalence is not known, but about 150 cases have been described so far. Hypouricemia is sometimes overlooked, that´s why we have set up the diagnostic flowchart. This consists of a) evaluation of uric acid concentrations in serum and urine with exclusion of primary renal hypouricemia, b) estimation of urinary xanthine, c) allopurinol loading test, which enables to distinguish type I and II; and finally assay of xanthine oxidoreductase activity in plasma with molecular genetic analysis. Following this diagnostic procedure we were able to find first patients with hereditary xanthinuria in our Czech population. We have detected nine cases, which is one of the largest group worldwide. Four patients were asymptomatic. All had profound hypouricemia, which was the first sign and led to referral to our department. Urinary concentrations of xanthine were in the range of 170-598 mmol/mol creatinine (normal < 30 mmol/mol creatinine). Hereditary xanthinuria is still unrecognized disorder and subjects with unexplained hypouricemia need detailed purine metabolic investigation.

Prevalence and complications of hypouricemia in a general population: A large-scale cross-sectional study in Japan.

BACKGROUNDS: Hypouricemia was reported as a risk factor for exercise-induced acute renal injury (EIAKI) and urinary stones. However, the prevalence of kidney diseases among hypouricemic subjects has not been evaluated. This study was conducted to clarify the prevalence of hypouricemia and the association of hypouricemia with kidney diseases by using a large-scale Japanese population data. METHODS: This study is a retrospective cross-sectional study at the Center for Preventive Medicine, St. Luke's International Hospital, Tokyo, Japan, and Sanin Rousai Hospital, Yonago, Japan. We analyzed the medical records of 90,143 Japanese subjects at the center in St. Luke's International Hospital, Tokyo, and 4,837 subjects in Sanin Rousai Hospital, Yonago, who underwent annual regular health check-up between January 2004 and June 2010. We defined hypouricemia as serum uric acid level of ≤2.0 mg/dL. We checked the medical history of all the study subjects and compared the rates of complications including urinary stones and kidney diseases among those with or without hypouricemia. RESULTS: The prevalence of hypouricemia was 0.19% in St. Luke's International Hospital, Tokyo, and 0.58% in Sanin Rousai Hospital, Yonago. The prevalence of hypouricemia in women was larger than that in men both in Tokyo (0.31% vs 0.068%, p<0.001) and in Yonago (1.237% vs 0.318%, p<0.001). Among 172 hypouricemic subjects (30 men), the rates of previous urinary stones and kidney diseases (including nephritis/nephrosis) were 1.2% (3.3% men, 0.7% women) and 2.3% (10% men, 0.7% women), respectively. Hypouricemic men had a 9-fold higher rate of previously having kidney diseases compared to non-hypouricemic men (p<0.001). However, the rates of other diseases including urinary stones were not significantly different between the two groups. CONCLUSIONS: Hypouricemia was associated with a history of kidney disease especially in men.

The impact of hypomagnesemia on erectile dysfunction in elderly, non-diabetic, stage 3 and 4 chronic kidney disease patients: a prospective cross-sectional study.

BACKGROUND: Erectile dysfunction (ED) is common in older men with chronic kidney disease. Magnesium is essential for metabolism of nitric oxide which helps in penile erection. There is little information available about the influence of serum magnesium on ED. The aim of the study was to assess the influence of hypomagnesemia on ED in elderly chronic kidney disease patients. SUBJECTS AND METHODS: A total of 372 patients aged 65-85 years, with an estimated glomerular filtration rate of 60-15 mL/min/1.73 m2, were divided into two groups according to serum magnesium levels: hypomagnesemia, n=180; and normomagnesemia, n=192. ED was assessed through the International Index of Erectile Function-5. Hypomagnesemia is defined as serum magnesium <1.8 mg/dL. RESULTS: The prevalence of ED was higher among hypomagnesemic subjects compared to that among normomagnesemics (93.3% vs 70.8%, P<0.001). Severe ED (62.8% vs 43.8%, P=0.037), mild-to-moderate ED (12.2% vs 5.2%, P=0.016), abdominal obesity (37.2% vs 22.9%, P=0.003), metabolic syndrome (38.4% vs 19.2%, P=0.026), proteinuria (0.83±0.68 vs 0.69±0.48 mg/dL, P=0.023), and C-reactive protein (6.1±4.9 vs 4.1±3.6 mg/L, P<0.001) were high; high-density lipoprotein cholesterol (48.8±14.0 vs 52.6±13.5 mg/dL, P=0.009), and albumin (4.02±0.53 vs 4.18±0.38 g/dL, P=0.001) were low in the hypomagnesemia group. Serum magnesium ≤1.85 mg/dL was the best cutoff point for prediction of ED. Hypomagnesemia (relative risk [RR] 2.27), age ≥70 (RR 1.74), proteinuria (RR 1.80), smoking (RR 21.12), C-reactive protein (RR 1.34), abdominal obesity (RR 3.92), and hypertension (RR 2.14) were predictors of ED. CONCLUSION: Our data support that ED is related to hypomagnesemia in elderly patients with moderately to severely reduced kidney function.

The Incidence of Cisplatin-induced Hypomagnesemia in Cervical Cancer Patients Receiving Cisplatin Alone.

Hypomagnesemia is one side effect in patients receiving cisplatin. However, there are few reports of cisplatin-induced hypomagnesemia in Japan. We retrospectively investigated the incidence of hypomagnesemia and nephrotoxicity in patients undergoing radiation therapy who were treated with cisplatin alone (dosage: 40 mg/m2, administration interval: 1 week) for cervical cancer. Thirty-two patients undergoing radiation therapy who received cisplatin alone for cervical cancer between January 2012 and May 2016 at Aichi Medical University Hospital were included. We measured patients' serum magnesium and creatinine levels on the day before cisplatin was administered. We utilized the RIFLE criteria (categorized into "risk", "injury", "failure", "loss", and "end-stage kidney disease") to define levels of cisplatin-induced nephrotoxicity, and classified cisplatin-induced nephrotoxicity into "risk" or "injury". Eighteen patients (56.3%) had cisplatin-induced hypomagnesemia, the majority of which occurred after the 4th treatment cycle. The number of patients with moderate renal dysfunction classified as "risk" in the hypomagnesemia group was not significantly higher than in the non-hypomagnesemia group (hypomagnesemia group=27.8%, non-hypomagnesemia group=7.1%; p=0.20). This survey sheds light on the incidence rates of cisplatin-induced hypomagnesemia in patients receiving cisplatin alone. We recommend monitoring the serum magnesium levels during cisplatin administration to prevent hypomagnesemia.