OBJECTIVE: To explore the clinical features and genetic etiology of a patient with primary distal renal tubular acidosis (dRTA). METHODS: A child who was diagnosed with primary dRTA at the Xi'an Children's Hospital in April 2021 due to poor appetite and persistent crying was selected as the study subject. Clinical data of the patient was collected. Whole exome sequencing (WES) was carried out for the child. Candidate variants were validated by Sanger sequencing of his family members. RESULTS: The child, a 1-month-and-18-day male, had featured poor appetite, persistent crying, poor weight gain and dehydration. Laboratory examination has suggested metabolic acidosis, hyperchloremia, hypokalemia, abnormal alkaline urine and anemia. Ultrasonographic examination of the urinary system revealed calcium deposition in renal medulla. DNA sequencing revealed that he has harbored compound heterozygous variants of the ATP6V0A4 gene, namely c.1363dupA (p.M455NfsX14) and c.2257C>T (p.Q753X), which were respectively inherited from his father and mother. Based on the guidelines from the American College of Medical Genetics and Genomics, both variants were classified as pathogenic (PVS1+PM3+PM2_Supporting). CONCLUSION The compound heterozygous variants of c.1363dupA (p.M455NfsX14) and c.2257C>T (p.Q753X) of the ATP6V0A4 gene probably underlay the pathogenesis of primary dRTA in this patient. Discovery of the c.2257C>T (p.Q753X) variant has also expanded the mutational spectrum of the ATP6V0A4 gene.
Humans ; Male ; Acidosis, Renal Tubular/genetics* ; Family ; Genomics ; Hypokalemia ; Infant

Distal renal tubular acidosis (dRTA) is characterized by hyperchloremic hypokalemic metabolic acidosis, nephrocalcinosis and metabolic bone disease. It has been associated with Southeast Asian Ovalocytosis (SAO), particularly in malaria endemic region. We present a case of an older adult with dRTA who presented with respiratory failure as a result of hyperchloremic normal anion gap metabolic acidosis, in association with nephrocalcinosis and SAO, however, without hypokalaemia due to concurrent acute kidney injury. Oxygen therapy was able to be weaned off after treatment with alkali supplementation. Distal RTA may be associated with SAO, and early recognition and treatment of dRTA is paramount in preventing complications such as chronic kidney disease, metabolic bone disease and life-threatening respiratory arrest.
Acidosis, Renal Tubular

Proximal renal tubular acidosis (RTA) is caused by a defect in bicarbonate (HCO₃⁻) reabsorption in the kidney proximal convoluted tubule. It usually manifests as normal anion-gap metabolic acidosis due to HCO₃⁻ wastage. In a normal kidney, the thick ascending limb of Henle’s loop and more distal nephron segments reclaim all of the HCO₃⁻ not absorbed by the proximal tubule. Bicarbonate wastage seen in type II RTA indicates that the proximal tubular defect is severe enough to overwhelm the capacity for HCO₃⁻ reabsorption beyond the proximal tubule. Proximal RTA can occur as an isolated syndrome or with other impairments in proximal tubular functions under the spectrum of Fanconi syndrome. Fanconi syndrome, which is characterized by a defect in proximal tubular reabsorption of glucose, amino acids, uric acid, phosphate, and HCO₃⁻, can occur due to inherited or acquired causes. Primary inherited Fanconi syndrome is caused by a mutation in the sodium-phosphate cotransporter (NaPₐ-II) in the proximal tubule. Recent studies have identified new causes of Fanconi syndrome due to mutations in the EHHADH and the HNF4A genes. Fanconi syndrome can also be one of many manifestations of various inherited systemic diseases, such as cystinosis. Many of the acquired causes of Fanconi syndrome with or without proximal RTA are drug-induced, with the list of causative agents increasing as newer drugs are introduced for clinical use, mainly in the oncology field.
Acidosis ; Acidosis, Renal Tubular ; Amino Acids ; Cystinosis ; Extremities ; Fanconi Syndrome ; Glucose ; Kidney ; Nephrons ; Sodium-Phosphate Cotransporter Proteins ; Uric Acid

No abstract available.
Acetazolamide ; Acidosis ; Acidosis, Renal Tubular ; Hypokalemic Periodic Paralysis ; Muscle Weakness

Primary distal renal tubular acidosis (dRTA) caused by mutations of the SLC4A1 gene, which encodes for erythroid and kidney isoforms of anion exchanger, shows marked difference in inheritance patterns and clinical features in different parts of the world. While the disease shows autosomal dominant inheritance without any red cell morphological abnormalities in the temperate countries, it is almost invariably recessive, and often accompanies red cell morphological abnormalities or hemolytic anemia in the tropics, especially in Southeast Asia. Here, we report three patients with autosomal recessive (AR) dRTA, presenting with typical findings of failure to thrive and rickets, from two unrelated Lao families. The mutational analyses revealed that all three patients harbored the same homozygous SLC4A1 mutation, p.Gly701Asp. Adequate supplementation of alkali and potassium resulted in remarkable improvement of growth retardation and skeletal deformities of the patients. This is the first case report of Lao patients with AR dRTA caused by SLC4A1 mutations.
Acidosis, Renal Tubular* ; Alkalies ; Anemia, Hemolytic ; Asia, Southeastern ; Congenital Abnormalities ; Failure to Thrive ; Humans ; Inheritance Patterns ; Kidney ; Laos ; Potassium ; Protein Isoforms ; Rickets ; Wills

Renal Fanconi syndrome (RFS) is caused by generalized proximal tubular dysfunction and can be divided into hereditary and acquired form. Adult-onset RFS is usually associated with drug toxicity or systemic disorders, and modern molecular genetics may explain the etiology of previous idiopathic cases of RFS. Here, we report the case of a 52-year-old woman with RFS whose etiology could not be identified. She presented with features of phosphaturia, renal glucosuria, aminoaciduria, tubular proteinuria, and proximal renal tubular acidosis. Her family history was unremarkable, and previous medications were nonspecific. Her bone mineral density was compatible with osteoporosis, serum intact parathyroid hormone level was mildly elevated, and 25(OH) vitamin D level was insufficient. Her blood urea nitrogen and serum creatinine levels were 8.4 and 1.19 mg/dL, respectively (estimated glomerular filtration rate, 53 mL/min/1.73 m²). Percutaneous renal biopsy was performed but revealed no specific renal pathology, including mitochondrial morphology. No mutation was detected in EHHADH gene. We propose the possibility of involvement of other genes or molecules in this case of adult RFS.
Acidosis, Renal Tubular ; Adult ; Biopsy ; Blood Urea Nitrogen ; Bone Density ; Creatinine ; Drug-Related Side Effects and Adverse Reactions ; Fanconi Syndrome ; Female ; Glomerular Filtration Rate ; Glycosuria, Renal ; Humans ; Hypophosphatemia, Familial ; Middle Aged ; Molecular Biology ; Osteoporosis ; Parathyroid Hormone ; Pathology ; Proteinuria ; Vitamin D

OBJECTIVETo study the clinical features of two families with distal renal tubular acidosis (dRTA) and mutations in the pathogenic gene SLC4A1.

METHODSFamily 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.

RESULTSThree 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.

CONCLUSIONSThis 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.

The electrogenic sodium/bicarbonate cotransporter 1 (NBCe1) on the basolateral side of the renal proximal tubule plays a pivotal role in systemic acid-base homeostasis. Mutations in the gene encoding NBCe1 cause severe proximal renal tubular acidosis accompanied by other extrarenal symptoms. The proximal tubule reabsorbs most of the sodium filtered in the glomerulus, contributing to the regulation of plasma volume and blood pressure. NBCe1 and other sodium transporters in the proximal tubule are regulated by hormones, such as angiotensin II and insulin. Angiotensin II is probably the most important stimulator of sodium reabsorption. Proximal tubule AT(1A) receptor is crucial for the systemic pressor effect of angiotensin II. In rodents and rabbits, the effect on proximal tubule NBCe1 is biphasic; at low concentration, angiotensin II stimulates NBCe1 via PKC/cAMP/ERK, whereas at high concentration, it inhibits NBCe1 via NO/cGMP/cGKII. In contrast, in human proximal tubule, angiotensin II has a dose-dependent monophasic stimulatory effect via NO/cGMP/ERK. Insulin stimulates the proximal tubule sodium transport, which is IRS2-dependent. We found that in insulin resistance and overt diabetic nephropathy, stimulatory effect of insulin on proximal tubule transport was preserved. Our results suggest that the preserved stimulation of the proximal tubule enhances sodium reabsorption, contributing to the pathogenesis of hypertension with metabolic syndrome. We describe recent findings regarding the role of proximal tubule transport in the regulation of blood pressure, focusing on the effects of angiotensin II and insulin.
Acidosis, Renal Tubular ; Angiotensin II ; Blood Pressure* ; Diabetic Nephropathies ; Homeostasis ; Humans ; Hypertension ; Insulin ; Insulin Resistance ; Kidney Tubules, Proximal ; Plasma Volume ; Rabbits ; Rodentia ; Sodium ; Sodium-Bicarbonate Symporters

Primary Sjögren's syndrome (pSS) is characterized by lymphocytic infiltration of the exocrine glands resulting in decreased saliva and tear production. It uncommonly involves the kidneys in various forms, including tubulointerstitial nephritis, renal tubular acidosis, Fanconi syndrome, and rarely glomerulonephritis. Its clinical symptoms include muscle weakness, periodic paralysis, and bone pain due to metabolic acidosis and electrolyte imbalance. Herein, we describe the cases of two women with pSS whose presenting symptoms involve the kidneys. They had hypokalemia and normal anion gap metabolic acidosis due to distal renal tubular acidosis and positive anti-SS-A and anti-SS-B autoantibodies. Since one of them experienced femoral fracture due to osteomalacia secondary to renal tubular acidosis, an earlier diagnosis of pSS is important in preventing serious complications.
Acid-Base Equilibrium ; Acidosis ; Acidosis, Renal Tubular* ; Autoantibodies ; Diagnosis ; Exocrine Glands ; Fanconi Syndrome ; Female ; Femoral Fractures ; Glomerulonephritis ; Humans ; Hypokalemia ; Kidney ; Muscle Weakness ; Nephritis, Interstitial ; Osteomalacia ; Paralysis ; Saliva ; Tears

Renal tubular acidosis (RTA) is a syndrome characterized by hyperchloremic metabolic acidosis and an inability to excrete highly acid urine, in which the impaired acid excretion is disproportional to the reduction in the glomerular filtration rate. Distal renal tubular acidosis (dRTA) is frequently associated with immune-mediated disease, including Sjogren's syndrome. Sjogren's syndrome is a systemic autoimmune disease that mainly affects exocrine glands, such as the lacrimal and salivary glands, resulting in xerophthalmia and xerostomia. Extraglandular manifestations are frequent and may include renal involvement. Recently, we experienced two cases of renal tubular acidosis in patients with Sjogren's syndrome. The first patient had lower extremity weakness and hypokalemia and the second had nephrocalcinosis. We discuss the frequency and pathogenesis of dRTA in Sjogren's syndrome.
Acidosis ; Acidosis, Renal Tubular* ; Autoimmune Diseases ; Exocrine Glands ; Glomerular Filtration Rate ; Humans ; Hypokalemia ; Lower Extremity ; Nephrocalcinosis ; Salivary Glands ; Sjogren's Syndrome* ; Xerophthalmia ; Xerostomia