Inherited Fanconi renotubular syndromes: unveiling the intricacies of hypophosphatemic rickets/osteomalacia.

INTRODUCTION: Fanconi renotubular syndromes (FRTS) are a rare group of inherited phosphaturic disorders with limited Indian as well as global data on this condition. Here, we describe the experience of a single Endocrinology center from Western India on FRTS. MATERIALS AND METHODS: Comprehensive clinical, biochemical, radiological, management, and genetic details of FRTS patients managed between 2010 and 2023 were collected and analyzed. RESULTS: FRTS probands had mutations (eight novel) in six genes [CLCN5 (n = 4), SLC2A2 (n = 2), GATM, EHHADH, HNF4A, and OCRL (1 each)]. Among 15 FRTS patients (11 families), rickets/osteomalacia was the most common (n = 14) presentation with wide inter- and intra-familial phenotypic variability. Delayed diagnosis (median: 8.8 years), initial misdiagnosis (8/11 probands), and syndrome-specific discriminatory features (8/11 probands) were commonly seen. Hypophosphatemia, elevated alkaline phosphatase, normal parathyroid hormone (median: 36 pg/ml), high-normal/elevated 1,25(OH)2D (median: 152 pg/ml), hypercalciuria (median spot urinary calcium to creatinine ratio: 0.32), and variable proximal tubular dysfunction(s) were observed. Elevated C-terminal fibroblast growth factor 23 in two probands was misleading, till the genetic diagnosis was reached. Novel observations in our FRTS cohort were preserved renal function (till sixth decade) and enthesopathy in FRTS1 and FRTS3 families, respectively. CONCLUSION: Our findings underscore frequent under- and misdiagnosis of FRTS; hence, a high index of suspicion for FRTS in phosphopenic rickets/osteomalacia, with early consideration of genetic testing is essential to ensure timely diagnosis of FRTS. The novel variants and phenotypic manifestations described here expand the disease spectrum of FRTS.

Successful autologous stem cell transplantation for light chain proximal tubulopathy with severe kidney injury.

Light chain proximal tubulopathy (LCPT) is a rare type of monoclonal gammopathy of renal significance. Clinicians should consider LCPT in the differential diagnosis of patients with renal or proximal tubular dysfunction with monoclonal gammopathy. They should confirm diagnosis by renal biopsy and initiate chemotherapy before disease progression.

Nocturnal enteral nutrition is therapeutic for growth failure in Fanconi-Bickel syndrome.

Fanconi-Bickel syndrome (FBS) is a rare autosomal recessive disorder characterised by impaired glucose liver homeostasis and proximal renal tubular dysfunction. It is caused by pathogenic variants in SLC2A2 coding for the glucose transporter GLUT2. Main clinical features include hepatomegaly, fasting hypoglycaemia, postprandial hyperglycaemia, Fanconi-type tubulopathy occasionally with rickets, and a severe growth disorder. While treatment for renal tubular dysfunction is well established, data regarding optimal nutritional therapy are scarce. Similarly, detailed clinical evaluation of treated FBS patients is lacking. These unmet needs were an incentive to conduct the present pilot study. We present clinical findings, laboratory parameters and molecular genetic data on 11 FBS patients with emphasis on clinical outcome under various nutritional interventions. At diagnosis, the patients' phenotypic severity could be classified into two categories: a first group with severe growth failure and rickets, and a second group with milder signs and symptoms. Three patients were diagnosed early and treated because of family history. All patients exhibited massive glucosuria at diagnosis and some in both groups had fasting hypoglycaemic episodes. Growth retardation improved drastically in all five patients treated by intensive nutritional intervention (nocturnal enteral nutrition) and uncooked cornstarch with final growth parameters in the normal range. The four severely affected patients who were treated with uncooked cornstarch alone did not catch up growth. All patients received electrolytes and l-carnitine supplementation to compensate for the tubulopathy. This is one of the largest series of FBS on therapeutic management with evidence that nocturnal enteral nutrition rescues growth failure.

Bone Fracture Risk and Renal Dysfunction in a Highly Cadmium Exposed Thai Population.

BACKGROUND: Paddy fields in the Mae Sot, Tak Province of Thailand are polluted with unsafe levels of cadmium (Cd). Elderly populations have a high Cd body burden, putting them at elevated risk of renal dysfunction and bone fractures. We aimed to compare bone fracture risk between glomerular dysfunction, proximal tubular dysfunction, and calcium (Ca) handling abnormalities. STUDY DESIGN: A cross-sectional study. METHODS: Serum osteocalcin and cross-linked N-telopeptide of type I collagen were used to detect bone metabolism abnormalities, whereas glomerular filtration rate, serum cystatin C, urinary ß2-microglobulin (ß2-MG) and fractional excretion of calcium (FECa) were used to indicate renal dysfunction. Urinary Cd was used as an exposure marker. RESULTS: FECa >2% was associated with high bone fracture risk in both genders. The adjusted odds of bone fracture risk were 6.029 and 3.288 in men and women, respectively with FECa >2% relative to the FECa < 2% group. Proximal tubular dysfunction and glomerular dysfunction did not significantly relate to the risk of bone fracture. CONCLUSIONS: Abnormal Ca handling is a key risk factor for bone fracture in Cd-exposed people. Men and women were at risk of bone fracture risk at a similar rate. FECa was a specific indicator of Ca wasting and was more cost-effective compared to ß2-MG and serum cystatin C. We recommend using FECa to monitor abnormal Ca metabolism in individuals with FECa>2%. Reduced renal toxicant exposure and Ca supplementation are recommended for Cd-exposed populations to reduce bone fracture risk.

Tenofovir-induced renal tubular dysfunction among human immunodeficiency virus patients on antiretroviral therapy in Nigeria: Prospects for early detection of presymptomatic nephrotoxicity.

BACKGROUND: Tenofovir disoproxil fumarate (TDF) is relatively safe, although renal toxicity has been reported. In Nigeria, there is insufficient data on renal toxicity among patients on TDF. This study assesses TDF-associated tubular dysfunction among human immunodeficiency virus (HIV) patients at a hospital in Nigeria. METHODS: In this cohort study, 104 adult HIV patients were recruited with a simple random technique from the outpatient clinic. Biochemical indices of renal function were estimated from serum and urine at the 16th and 24th week after an initial assessment at baseline. RESULTS: There were no significant differences in baseline proteinuria or glycosuria between TDF and non-TDF groups. Mean baseline urine and serum parameters did not differ significantly between the two groups (P > 0.05). In the TDF group, all urine parameters differed significantly between baseline and 24th week values (P < 0.001). After 16 weeks, mean urine phosphate and urine uric acid increased significantly (P < 0.05) by 2.97 mg/dL and 50.9 mg/dL, respectively, in the TDF group. The rise in mean urine glucose from baseline to the 24th week was more marked in the TDF than the non-TDF group (0.25 vs. 0.07 mmol/L). Higher mean differences in urine albumin were also recorded in the TDF group from baseline to the 24th week. CONCLUSION: Indicators of tubular dysfunction were markedly higher among patients on the TDF-based treatment regimen. Biomarkers of tubular dysfunction could be useful for detecting pre-symptomatic nephrotoxicity before marked reduction of glomerular filtration rate in HIV patients on TDF.

Una nueva mutación de la enfermedad de Dent en un niño de 11 años con nefrolitiasis y nefrocalcinosis / A novel mutation of Dent's disease in an 11-year-old male with nephrolithiasis and nephrocalcinosis

La enfermedad de Dent es una tubulopatía recesiva ligada al cromosoma X caracterizada por proteinuria de bajo peso molecular (bpm), hipercalciuria, nefrocalcinosis o nefrolitiasis, disfunción tubular proximal e insuficiencia renal en la adultez. Las mujeres son portadoras y, en general, padecen una forma leve de la enfermedad. La progresión hacia la insuficiencia renal en estadio terminal se da entre los 30 y los 50 años de edad en el 30-80% de los varones afectados. A falta de un tratamiento dirigido al defecto molecular, en la actualidad, los pacientes con enfermedad de Dent reciben tratamientos complementarios orientados a prevenir la nefrolitiasis y la nefrocalcinosis. El caso que presentamos es el de un niño de 11 años con nefrocalcinosis y nefrolitiasis, en quien se detectó una nueva mutación en el gen CLCN5.

Dent's disease is a rare X-linked recessive tubulopathy characterized by low molecular weight (LMW) proteinuria, hypercalciuria, nephrolcalcinosis or nephrolithiasis, proximal tubular dysfunction and renal failure in adulthood. Females are carriers and usually mildly affected. Progression to endstage renal failure are at the 3rd-5th decades of life in 30-80% of affected males. In the absence of therapy targeting for the molecular defect, the current care of patients with Dent's disease is supportive, focusing on the prevention of nephrolithiasis and nephrocalcinosis. We present an 11-year-old child with nephrocalcinosis and nephrolithiasis caused by a new mutation at CLCN5 gene.

Tenofovir-induced renal tubular dysfunction among human immunodeficiency virus patients on antiretroviral therapy in Nigeria: Prospects for early detection of presymptomatic nephrotoxicity

BACKGROUND: Tenofovir disoproxil fumarate (TDF) is relatively safe, although renal toxicity has been reported. In Nigeria, there is insufficient data on renal toxicity among patients on TDF. This study assesses TDF-associated tubular dysfunction among human immunodeficiency virus (HIV) patients at a hospital in Nigeria. METHODS: In this cohort study, 104 adult HIV patients were recruited with a simple random technique from the outpatient clinic. Biochemical indices of renal function were estimated from serum and urine at the 16th and 24th week after an initial assessment at baseline. RESULTS: There were no significant differences in baseline proteinuria or glycosuria between TDF and non-TDF groups. Mean baseline urine and serum parameters did not differ significantly between the two groups (P > 0.05). In the TDF group, all urine parameters differed significantly between baseline and 24th week values (P < 0.001). After 16 weeks, mean urine phosphate and urine uric acid increased significantly (P < 0.05) by 2.97 mg/dL and 50.9 mg/dL, respectively, in the TDF group. The rise in mean urine glucose from baseline to the 24th week was more marked in the TDF than the non-TDF group (0.25 vs. 0.07 mmol/L). Higher mean differences in urine albumin were also recorded in the TDF group from baseline to the 24th week. CONCLUSION: Indicators of tubular dysfunction were markedly higher among patients on the TDF-based treatment regimen. Biomarkers of tubular dysfunction could be useful for detecting pre-symptomatic nephrotoxicity before marked reduction of glomerular filtration rate in HIV patients on TDF.

Higher Prevalence and Faster Progression of Chronic Kidney Disease in Human Immunodeficiency Virus-Infected Middle-Aged Individuals Compared With Human Immunodeficiency Virus-Uninfected Controls.

Background: Human immunodeficiency virus (HIV)-infected individuals are at increased risk of chronic kidney disease (CKD). Human immunodeficiency virus infection, traditional CKD risk factors, and combination antiretroviral therapy (cART) may all contribute. Methods: We compared prevalence of renal impairment (estimated glomerular filtration rate [eGFR] <60 mL/min/1.73m2), albuminuria (albumin/creatinine ratio ≥3 mg/mmol), and proximal renal tubular dysfunction (retinol-binding protein/creatinine ratio >2.93µg/mmol and/or fractional phosphate excretion >20% with plasma phosphate <0.8 mmol/L) in 596 HIV-infected and 544 HIV-uninfected AGEhIV Cohort Study participants. We also assessed whether being HIV-infected on cART, with follow-up censored when cART regimen was modified, was associated with greater eGFR decline or worsening albuminuria (increase ≥10%/year with change in albuminuria category). Results: Human immunodeficiency virus infection was independently associated with renal impairment (adjusted odds ratio [aOR] = 2.1; 95% confidence interval [CI] = 1.0-4.4), albuminuria (aOR = 5.8; 95% CI = 3.7-9.0), and proximal renal tubular dysfunction (aOR = 7.0; 95% CI = 4.9-10.2]). Among 377 HIV-infected and 479 HIV-uninfected individuals (median follow-up = 3.9/4.1 years, respectively) included in longitudinal analyses, being HIV-infected and remaining on unmodified cART was independently associated with greater eGFR decline (-0.56; 95% CI = -0.87 to -0.24 mL/min/1.73m2/year) and worsening albuminuria (aOR = 2.3; 95% CI = 1.3-4.0). Conclusions: In these middle-aged individuals, HIV infection was independently associated with renal impairment, albuminuria, and proximal renal tubular dysfunction. Human immunodeficiency virus-infected individuals on cART (predominantly containing tenofovir disoproxil fumarate) were also more likely to experience eGFR decline and worsening albuminuria compared with HIV-uninfected individuals.

Arthrogryposis-renal tubular dysfunction-cholestasis syndrome: a cause of neonatal cholestasis. Case report.

Arthrogryposis-renal dysfunction-cholestasis syndrome is a rare lethal disorder that involves multipl organ system. It is inherited autosomal recessive and caused by defects in the VPS33B and VIPAR genes. Three cardinal findings of this syndrome are arthrogryposis, renal tubular dysfunction and cholestasis.The other organ involvements including ichthyosis, central nervous system malformation, platelet anomalies, congenital heart defects and severe failure to thrive are sometimes associated with this syndrome. Clinical findings, organ biopsy and mutational analysis can help for diagnosing but there is no curative treatment except supportive care. Several symptoms of this condition are already usually present in the neonatal period: arthrogryposis, neonatal cholestasis, skin lesions, among others. Usually survival is until the first year of life. We present a newborn whose evolution was rapidly fatal.

El síndrome de artrogriposis, disfunción tubular renal y colestasis es un trastorno fatal infrecuente que compromete múltiples aparatos y sistemas de órganos. Es un trastorno autosómico recesivo hereditario, causado por defectos en los genes VPS33B y VIPAR. Los tres signos primordiales de este síndrome son la artrogriposis, la disfunción tubular renal y la colestasis. Otros compromisos orgánicos a veces asociados con este síndrome son ictiosis, malformación del sistema nervioso central, anomalías trombocíticas, defectos cardíacos congénitos y grave retraso del crecimiento. Las manifestaciones clínicas, la biopsia de un órgano y los análisis de mutaciones pueden ayudar con el diagnóstico, pero no existe un tratamiento curativo; solamente puede instaurarse un tratamiento sintomático. Varios síntomas de esta afección usualmente se manifiestan en el período neonatal: artrogriposis, colestasis neonatal, lesiones cutáneas, entre otros. En general, la supervivencia se prolonga hasta el primer año de vida. Presentamos el caso de una recién nacida con una rápida evolución y desenlace fatal.

Topiramate as a rare cause of reversible Fanconi syndrome and acute kidney injury: a case report and literature review.

Topiramate (TPM) is a sulfa-derivative monosaccharide that has been used for multiple indications in the last several years. We describe a 53-year-old woman with known chronic kidney disease stage 2 and baseline creatinine of 1 mg/dL who developed acute kidney injury and proximal renal tubular dysfunction while on TPM for depression. The Naranjo Adverse Drug Reaction Probability Scale indicated a probable relationship (score of 6) between TPM and acute kidney injury as well as proximal tubular dysfunction; these renal conditions resolved on withdrawal of TPM. To our knowledge, this is the first report of such a scenario. Patients receiving TPM therapy should be closely monitored for evidence of kidney dysfunction and electrolyte abnormalities.

Síndrome de artrogriposis, disfunción tubular renal y colestasis: causa de colestasis neonatal. A propósito de un caso / Arthrogryposis-renal tubular dysfunction-cholestasis syndrome: a cause of neonatal cholestasis. Case report

El síndrome de artrogriposis, disfunción tubular renal y colestasis es un trastorno fatal infrecuente que compromete múltiples aparatos y sistemas de órganos. Es un trastorno autosómico recesivo hereditario, causado por defectos en los genes VPS33B y VIPAR. Los tres signos primordiales de este síndrome son la artrogriposis, la disfunción tubular renal y la colestasis. Otros compromisos orgánicos a veces asociados con este síndrome son ictiosis, malformación del sistema nervioso central, anomalías trombocíticas, defectos cardíacos congénitos y grave retraso del crecimiento. Las manifestaciones clínicas, la biopsia de un órgano y los análisis de mutaciones pueden ayudar con el diagnóstico, pero no existe un tratamiento curativo; solamente puede instaurarse un tratamiento sintomático. Varios síntomas de esta afección usualmente se manifiestan en el período neonatal: artrogriposis, colestasis neonatal, lesiones cutáneas, entre otros. En general, la supervivencia se prolonga hasta el primer año de vida. Presentamos el caso de una recién nacida con una rápida evolución y desenlace fatal.

Arthrogryposis-renal dysfunction-cholestasis syndrome is a rare lethal disorder that involves multipl organ system. It is inherited autosomal recessive and caused by defects in the VPS33B and VIPAR genes. Three cardinal findings of this syndrome are arthrogryposis, renal tubular dysfunction and cholestasis.The other organ involvements including ichthyosis, central nervous system malformation, platelet anomalies, congenital heart defects and severe failure to thrive are sometimes associated with this syndrome. Clinical findings, organ biopsy and mutational analysis can help for diagnosing but there is no curative treatment except supportive care. Several symptoms of this condition are already usually present in the neonatal period: arthrogryposis, neonatal cholestasis, skin lesions, among others. Usually survival is until the first year of life. We present a newborn whose evolution was rapidly fatal.

Incidence and predictors of end-stage renal disease in outpatients with systolic heart failure.

BACKGROUND: Renal dysfunction is an important prognostic factor in heart failure (HF), but whether this dysfunction progresses to end-stage renal disease (ESRD) is unknown. Therefore, we examined incidence and predictors of ESRD in outpatients with HF. METHODS AND RESULTS: Patients with systolic HF were identified in The Danish Heart Failure database and new-onset ESRD from the Danish Registry on Dialysis. Renal function was estimated by The Chronic Kidney Disease Epidemiology Collaboration equation and patients grouped by estimated glomerular filtration rate (eGFR)-group I: ≥60 mL/min per 1.73 m(2), group II: 30 to 59 mL/min per 1.73 m(2), group III: 15 to 29 mL/min per 1.73 m(2), group IV: <15 mL/min per 1.73 m(2). Cox hazard models for time to ESRD, to death, and the composite end point of ESRD or death were constructed and predictors of ESRD identified. A total of 8204 patients were included in the analyses. Median age was 70 years (Q, 61-77), 28% were women, median left ventricular ejection fraction was 30% (Q, 24-40), and median eGFR was 68 (Q, 51-85) mL/min per 1.73 m(2). Forty-one patients developed ESRD (1.3/1000 patient-years). Baseline eGFR group II (P<0.001), eGFR group III (P<0.001), eGFR group IV (P<0.001), uncontrolled hypertension (P=0.049), need of diuretics, and age <60 years (P=0.016) were associated with time to ESRD. CONCLUSIONS: ESRD is rare in outpatients with systolic HF and is mainly observed in patients with an eGFR <30 mL/min per 1.73 m(2). A low eGFR, age <60 years, need of diuretics, and uncontrolled hypertension identify patients with an increased risk for ESRD.