Project description:OBJECTIVE:Primary distal renal tubular acidosis (dRTA) is a rare genetic disease characterized by distal tubular dysfunction leading to metabolic acidosis and alkaline urine. Growth retardation is a major concern in these children. The disease is caused by defects in at least three genes (SLC4A1, ATP6V0A4, and ATP6V1B1) involved in urinary distal acidification. Several series of dRTA patients from different ethnic backgrounds have been genetically studied, but genetic studies regarding Chinese population is rare. Our aim was to investigate the clinical features and genetic basis of primary dRTA in Chinese children. METHODS:Three unrelated patients with dRTA participated in our study. Next-generation sequencing was performed, and the findings were validated using the Sanger sequencing method. RESULTS:All patients exhibited hyperchloraemic metabolic acidosis, abnormally high urine pH, hypokalemia, and nephrocalcinosis. Growth retardation was observed in all patients. During the follow-up (range 1-4 years), alkali replacement therapy corrected the systemic metabolic acidosis, and two patients demonstrated normal growth. rhGH therapy was administered to patient-3 at the age of 6?years, and his growth rate was significantly improved (growth velocity 9.6?cm/yr). In total, 5 mutations were identified in our cohort of three patients, and four mutations were novel. CONCLUSIONS:We report the clinical and molecular characteristics of dRTA patients from China. The four novel mutations detected in our study extend the spectrum of gene mutations associated with primary dRTA. Furthermore, our study confirms the effect of early treatment in improving growth for dRTA patient and provides insight into the effects of rhGH on dRTA patients who were diagnosed late and exhibiting a persistent growth delay despite appropriate therapy.
Project description:Distal renal tubular acidosis (dRTA) is characterized by metabolic acidosis due to uric acid dysfunction. The aim of this study was to demonstrate the genetic diagnosis of Chinese children with dRTA by whole-exome sequencing. From Jan. 2010 to Sept. 2015, 16 children with dRTA were recruited to investigate the possibility of genetic diagnosis and to examine any genotype-phenotype relationships in these patients. Sanger sequencing was used to confirm mutations identified by whole-exome sequencing. Clinical and biological features in the patients included hyperchloremic metabolic acidosis, impaired growth, hypokalemia, nephrocalcinosis, nephrolithiasis, hypercalciuria, hypocitraturia, and rickets or osteomalacia. Seventeen mutations in the solute carrier family 4 member 1 (SLC4A1), ATPase H+ transporting V0 subunit a4 (ATP6V0A4), ATPase H+ transporting V1 subunit B1 (ATP6V1B1), WNK lysine deficient protein kinase 1 (WNK1) and the claudin 16 (CLDN16) were identified in 15 patients, and 14 of these mutations are novel. Only 1 patient was negative for any mutations. Our results demonstrate the existence of SLC4A1, ATP6V1B1, ATP6V0A4, WNK1 and CLDN16 mutations in Chinese children with dRTA and indicate that compound heterozygosity at 2 or more different but related genes can be responsible for its pathogenesis. This study also indicates that whole-exome sequencing is a labor and cost-effective means of analyzing dRTA-associated genes.
Project description:Renal tubular acidosis (RTA) is a condition characterized by normal anion gap metabolic acidosis. Type 1 and type 2 RTA are the most common, and are caused by defective secretion of hydrogen ions and impaired absorption of bicarbonate, respectively. Long-standing uncorrected acidosis can lead to metabolic bone disease (MBD). Rickets and osteomalacia remain the commonest manifestations of uncorrected RTA. In addition, there can be a myriad of other skeletal manifestations like fractures, pseudofractures, secondary osteoporosis and even sclerotic bone disease. The postulated mechanism for bone involvement includes acidosis-mediated exaggerated osteoclastic bone resorption. Other contributory factors include abnormal renal handling of phosphate leading to hypophosphataemia in proximal RTA, and impaired vitamin D metabolism and action. In distal RTA, hypercalciuria and secondary hyperparathyroidism may play a key role for bone involvement. Recognizing the disease in its early course is important to prevent permanent sequelae of skeletal involvement. Most of these patients may, in fact, undergo orthopaedic interventions without primary correction of acidosis. We describe five cases who presented with MBD in varied forms. While evaluating the aetiology of MBD, they were diagnosed with RTA. Subsequently, we attempted to analyse the causes of RTA. Although the common causes were ruled out, genetic aetiology could not be ascertained due to resource constraints. RTA remains an important differential diagnosis of MBD. More awareness is required to diagnose the disease early and to treat it adequately. Our case series is an attempt to provide the clinical, biochemical and skeletal spectrum of RTA. In addition, we have attempted to provide algorithms for the approach and evaluation of RTA along with their varied causes.
Project description:Hyperchloremic acidosis is frequent in critically ill patients. Renal tubular acidosis (RTA) may contribute to acidemia in the state of hyperchloremic acidosis, but the prevalence of RTA has never been studied in critically ill patients. Therefore, we aimed to investigate the prevalence, type, and possible risk factors of RTA in critically ill patients using a physical-chemical approach.This prospective, observational trial was conducted in a medical ICU of a university hospital. One hundred consecutive critically ill patients at the age ?18, expected to stay in the ICU for ?24 h, with the clinical necessity for a urinary catheter and the absence of anuria were included. Base excess (BE) subset calculation based on a physical-chemical approach on the first 7 days after ICU admission was used to compare the effects of free water, chloride, albumin, and unmeasured anions on the standard base excess. Calculation of the urine osmolal gap (UOG)--as an approximate measure of the unmeasured urine cation NH4(+)--served as determinate between renal and extrarenal bicarbonate loss in the state of hyperchloremic acidosis.During the first week of ICU stay 43 of the patients presented with hyperchloremic acidosis on one or more days represented as pronounced negative BEChloride. In 31 patients hyperchloremic acidosis was associated with RTA characterized by a UOG ?150 mosmol/kg in combination with preserved renal function. However, in 26 of the 31 patients with RTA metabolic acidosis was neutralized by other acid-base disturbances leading to a normal arterial pH.RTA is highly prevalent in critically ill patients with hyperchloremic acidosis, whereas it is often neutralized by the simultaneous occurrence of other acid-base disturbances.Clinicaltrials.gov NCT02392091. Registered 17 March 2015.
Project description:Autosomal recessive distal renal tubular acidosis is usually a severe disease of childhood, often presenting as failure to thrive in infancy. It is often, but not always, accompanied by sensorineural hearing loss, the clinical severity and age of onset of which may be different from the other clinical features. Mutations in either ATP6V1B1 or ATP6V0A4 are the chief causes of primary distal renal tubular acidosis with or without hearing loss, although the loss is often milder in the latter. We describe a kindred with compound heterozygous alterations in ATP6V0A4, where hearing loss was formally diagnosed late in both siblings such that they missed early opportunities for hearing support. This kindred highlights the importance of routine audiologic assessments of all children with distal renal tubular acidosis, irrespective either of age at diagnosis or of which gene is mutated. In addition, when diagnostic genetic testing is undertaken, both genes should be screened irrespective of current hearing status. A strategy for this is outlined.
Project description:Renal tubular acidosis (RTA) comprises a group of disorders in which excretion of hydrogen ions or reabsorption of filtered HCO3 is impaired, leading to chronic metabolic acidosis with normal anion gap. In the current review, the focus is placed on the most common type of RTA, Type 1 RTA or Distal RTA (dRTA), which is a rare chronic genetic disorder characterized by an inability of the distal nephron to secrete hydrogen ions in the presence of metabolic acidosis. Over the years, knowledge of the molecular mechanisms behind acid secretion has improved, thereby greatly helping the diagnosis of dRTA. The primary or inherited form of dRTA is mostly diagnosed in infancy, childhood, or young adulthood, while the acquired secondary form, as a consequence of other disorders or medications, can happen at any age, although it is more commonly seen in adults. dRTA is not as "benign" as previously assumed, and can have several, highly variable long-term consequences. The present review indeed reports and summarizes both clinical symptoms and diagnosis, long-term outcomes, genetic inheritance, epidemiology and current treatment options, with the aim of shedding more light onto this rare disorder. Being a chronic condition, dRTA also deserves attention in the transition between pediatric and adult nephrology care, and as a rare disease it has a place in the European and Italian rare nephrological diseases network.
Project description:BackgroundHereditary spherocytosis (HS) and hereditary hereditary distal renal tubular acidosis (dRTA) are associated with mutations in the SLC4A1 gene encoding the anion exchanger 1. In this study, some patients with clinical evidence of congenital HS and renal symptoms were investigated.MethodsTwelve patients with congenital HS and renal symptoms were recruited from Ali-Asghar Children’s Hospital (Tehran, Iran). A patient suspected of having dRTA was examined using whole exome sequencing method, followed by Sanger sequencing.ResultsOne patient (HS03) showed severe failure to thrive, short stature, frequent urinary infection, and weakness. A homozygote (rs571376371 for c.2494C>T; p.Arg832Cys) and a heterozygote (rs377051298 for c.466C>T; p.Arg156Trp) missense variant were identified in the SLC4A1 and SPTA1 genes, respectively. The compound heterozygous mutations manifested as idRTA and severe HS in patient HS03.ConclusionOur observations, for the first time, revealed clinical and genetic characteristics of idRTA and severe HS in an Iranian patient HS03.
Project description:OBJECTIVE:To study the clinical features of two families with distal renal tubular acidosis (dRTA) and mutations in the pathogenic gene SLC4A1. METHODS:Family investigation, medical history collection, and measurement of biochemical parameters were performed to analyze the clinical phenotype and genetic characteristics of dRTA. Direct sequencing was used to detect SLC4A1 gene mutations. RESULTS:Three patients in these two families (two of them were mother and son) were diagnosed with dRTA with typical clinical features, including short stature, metabolic acidosis, alkaline urine, hypokalemia, and nephrocalcinosis. SLC4A1 gene analysis showed that all the three patients had a pathogenic missense mutation R589H (c.1766G>A). The child in family 1 had a de novo mutation of SLC4A1, and the child in family 2 had an SLC4A1 gene mutation inherited from the mother, which met the characteristic of autosomal dominant inheritance. CONCLUSIONS:This study reports the R589H mutation in SLC4A1 gene in families with hereditary dRTA for the first time in China. Clinical physicians should perform gene detection for patients suspected of hereditary dRTA to improve the diagnosis and treatment of this disease.
Project description:This report describes the oral manifestations of renal tubular acidosis (RTA) associated with secondary rickets and discusses the biological plausibility of these findings. The characteristic electrolyte changes during RTA or genetic mutations that trigger RTA may be responsible for impaired amelogenesis, dental malocclusion, impacted teeth, and absent lamina dura. This report reinforces the possibility of an association between RTA and the oral manifestations described.