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PubMed1999

Localization of a gene for autosomal recessive distal renal tubular acidosis with normal hearing (rdRTA2) to 7q33-34.

Failure of distal nephrons to excrete excess acid results in the "distal renal tubular acidoses" (dRTA). Early childhood features of autosomal recessive dRTA include severe metabolic acidosis with inappropriately alkaline urine, poor growth, rickets, and renal calcification. Progressive bilateral sensorineural hearing loss (SNHL) is evident in approximately one-third of patients. We have recently identified mutations in ATP6B1, encoding the B-subunit of the collecting-duct apical proton pump, as a cause of recessive dRTA with SNHL. We now report the results of genetic analysis of 13 kindreds with recessive dRTA and normal hearing. Analysis of linkage and molecular examination of ATP6B1 indicated that mutation in ATP6B1 rarely, if ever, accounts for this phenotype, prompting a genomewide linkage search for loci underlying this trait. The results strongly supported linkage with locus heterogeneity to a segment of 7q33-34, yielding a maximum multipoint LOD score of 8.84 with 68% of kindreds linked. The LOD-3 support interval defines a 14-cM region flanked by D7S500 and D7S688. That 4 of these 13 kindreds do not support linkage to rdRTA2 and ATP6B1 implies the existence of at least one additional dRTA locus. These findings establish that genes causing recessive dRTA with normal and impaired hearing are different, and they identify, at 7q33-34, a new locus, rdRTA2, for recessive dRTA with normal hearing.

Acidosis, Renal Tubular↗
PubMed2002

Type IV renal tubular acidosis presenting as dyspnea in two older patients taking angiotensin-converting enzyme inhibitors.

The evaluation of dyspnea most often leads to a cardiac or pulmonary diagnosis. In the elderly, however, the cause is commonly multifactorial. The emergency physician should always consider noncardiopulmonary etiologies when treating such patients. We present 2 cases of new-onset type IV renal tubular acidosis (RTA) in older patients taking lisinopril who presented to the emergency department as dyspnea. Both patients had chronic cardiopulmonary illnesses and were initially diagnosed as having either congestive heart failure, asthma exacerbations, or both. The laboratory results for RTA are specific and the diagnosis can be made in the ED.

Aged↗
PubMed1997

Incomplete distal renal tubular acidosis coinherited with a mutation in the band 3 (AE1) gene.

BACKGROUND: Band 3 (anion exchanger 1, AE1) is one of the most abundant proteins of the erythrocyte membrane. We have previously characterized twenty AE1 gene defects underlying spherocytic haemolytic anaemia with band 3 deficiency. Since AE1 is also expressed in the intercalated cells of renal cortical collecting ducts where it is thought to participate in urine acidification, we asked whether the spherocytogenic AE1 mutations also affect the regulation of urine acidity. METHODS: We examined 10 patients from seven unrelated families with hereditary spherocytosis with band 3 deficiency using the short urine acidification test with CaCl2 administration at a dose of 0.2 g/kg b.w. To asses the ability of the nephron to secrete protons, 400 ml of NaHCO3 were infused over a period of 2 h. RESULTS: While we detected no significant abnormalities in eight patients, we have diagnosed incomplete distal renal tubular acidosis (dRTA) in two patients from one family whose urinary pH 5 h after CaCl2 administration were 6.56 and 6.89. Administration of bicarbonate in these two patients resulted in high urinary HCO3- concentration. The patients carry the previously characterized mutation band 3PRIBRAM that encodes a C-terminally truncated band 3 containing only the cytoplasmic domain and the first three putative transmembrane segments. CONCLUSIONS: This finding shows an association of a band 3 defect with abnormal urinary acidification perhaps secondary to Cl-/HCO3- exchange in the basolateral membrane of alpha-intercalated cells of cortical collecting ducts.

Acidosis↗
PubMed1979

Congenital persistent proximal type renal tubular acidosis in two brothers.

Two brothers showed severe and persistent hyperchloraemic metabolic acidosis (capillary blood pH 7.07--7.15) due to a low renal bicarbonate threshold at 11 mmol/l. The maximal tubular capacity for bicarbonate reabsorption was reduced to about half the normal. A high dose of acetazolamide (25 mg/kg) lowered the tubular bicarbonate reabsorption substantially, indicating the presence of carbonic anhydrase. Both the glomerular filtration rate, the renal blood flow and the renal concentrating capacity were slightly reduced. The clinical characteristics were: growth retardation, mental retardation, nystagmus, corneal opacities, cataract, glaucoma and enamel defects of the permanent teeth. Serum thyroxine was pathological low without clinical signs of hypothyreosis. The erythrocytes showed an increased osmotic resistance. Autopsy of the younger brother, who died 4 1/2 years old, revealed thyroid and thymus weights of 25% of the normal. The kidney tubular cells were swollen with vacuoles. The glomeruli had a normal appearance.

Acetazolamide↗
PubMed1981

Distal renal tubular acidosis in multiple myeloma.

A patient with early multiple myeloma was initially seen with a severe hyperchloremic metabolic acidosis with a normal anion gap and a urine pH of 6.3. The patient did not have glucosuria, aminoaciduria, of phosphaturia. A bicarbonate loading test showed that the fractional excretion of bicarbonate was less than 5% and confirmed the hypothesis that the patient had a distal renal tubular acidification defect. The pathophysiologic mechanism that caused this defect is unknown, but it is associated with the presence of a serum M component (IgG-lambda) and a urine M component (lambda light chains). Multiple myeloma should be considered in the differential diagnosis of conditions of patients who have a renal tubular acidification defect.

Acidosis, Renal Tubular↗
PubMed1982

Renal tubular acidosis with simultaneous lactic and keto acidoses: unusual manifestations of acute myelomonoblastic leukemia.

A 16-year-old male with severe metabolic acidosis required huge doses of sodium bicarbonate to alleviate his symptoms. Subsequent investigation showed that his bone marrow and kidneys were infiltrated with myelomonoblasts. His clinical course showed a temporal relationship between acute myelomonoblastic leukemia and metabolic acidosis. The literature on various etiologies of metabolic acidosis is reviewed. This is probably the first documented case of acute leukemia with the simultaneous occurrence of renal tubular, lactic and ketoacidoses.

Acidosis↗
PubMed1990

[Osteomalacia and renal tubular acidosis associated with analgesic abuse. A clinical case].

Osteomalacia is a multifactorial bone disorder. Main causes are vitamin D deficiency and phosphorus depletion. Among patients with renal insufficiency the incidence of osteomalacia is variable and probable related to impairment of the synthesis of 1,25 dihydroxy-vitamin D3 (calcitriol). We report a patients with severe osteomalacia, hyperkalemic tubular acidosis, low serum calcitriol levels and insufficiency associated to a prolonged overuse of analgesic drugs. Differential diagnosis and pathophysiology are discussed.

Acidosis, Renal Tubular↗
PubMed1976

Hyperkalemia unresponsive to massive doses of aldosterone and renal tubular acidosis in a patient with chronic interstitial nephritis: clinical and experimental studies.

A unique 53-year-old male patient is described in whom aldosterone-refractory hyperkalemia and renal tubular acidosis/RTA/ was due to chronic interstitial nephritis associated with peritubular hyaline deposits in the distal nephron. Hyperkalemia was not caused by an adrenal disorder or acidosis and could not be abolished by interventions enhancing K clearance; saline infusions, high doses of furosemide, cortisone, cortisol, long-acting synthetic ACTH and excessive doses of aldosterone. Glucocorticoids induced a marked decrease in sodium excreting capacity probably by an action on the ascending limb of Henle's loop while aldosterone elicited a paradoxical natriuretic response by unknown mechanism. The results of our experimental studies carried out on the hyperkalemic RTA patient as well as on various control subjects and patients suggest 1. a specific defect in renal K excretion associated with decreased aldosterone responsiveness of the tubules presumably due to the peritubular pathology, and 2. a disturbance in the cellular regulation of K distribution between fluid compartments of unknown origin.

Acidosis, Renal Tubular↗
PubMed1994

Renal tubular acidosis in Papua New Guinea.

Unlike most other inborn errors of metabolism, which require advanced and expensive diagnostic techniques and complex drug and dietary management (often not feasible in developing countries), the renal tubular acidoses may be detected and treated both easily and cheaply. Diagnostic confusion is possible as this series demonstrates due to the protean clinical manifestations. Three recent cases from Port Moresby General Hospital are described and appropriate investigations and treatment discussed.

Acidosis, Renal Tubular↗
PubMed1993

[Classification of renal tubular acidosis. Recent data].

In normal adults eating diets with standard protein contents, urinary excretion of NH4 approximates 40 mmol/24 hours and urinary pH is variable. In patients with metabolic acidosis, a urinary pH under 5.5 suggests an extra-renal cause whereas a urinary pH above 5.5 suggests a renal disorder, although there are many exceptions to this rule of thumb. However, urinary excretion of NH4 is always above 70 mmol/24 hours in extra-renal acidosis and less than or equal to 40 mmol/24 hours in renal acidosis; the two situations can readily be differentiated by determining the urinary anion gap which is absent in the former case and present in the latter. Acidosis due to nephron loss is readily diagnosed on the basis of advanced renal failure with an elevation in nonassayed plasma anions, contrasting with the increased serum chloride level found in tubular acidosis. Oral NaHCO3 loading followed by determination of the fractional excretion of HCO3 or, preferably, of the TmHCO3 normalized for glomerular filtration rate differentiates proximal tubular acidosis (decreased TmHCO3) from distal tubular acidosis (normal or increased TmHCO3). In the latter case, decreased serum potassium levels suggest distal tubular acidosis due to defective H(+)-ATPase or H+/K(+)-ATPase pump function (no increase in urinary PCO2 after oral NaHCO3 loading) or to inability of the kidney to develop a normal H+ gradient (normal increase in urinary PCO2). Increased serum potassium levels suggest conditions involving either hypoaldosteronism or alterations in transepithelial voltage or pseudo-hypoaldosteronism. The incidence of distal tubular acidosis with increased serum potassium levels is rising, whereas tubular acidosis with low serum potassium levels remains infrequent.

Acid-Base Equilibrium↗
PubMed2000

Mutations in ATP6N1B, encoding a new kidney vacuolar proton pump 116-kD subunit, cause recessive distal renal tubular acidosis with preserved hearing.

The multi-subunit H+-ATPase pump is present at particularly high density on the apical (luminal) surface of -intercalated cells of the cortical collecting duct of the distal nephron, where vectorial proton transport is required for urinary acidification. The complete subunit composition of the apical ATPase, however, has not been fully agreed upon. Functional failure of -intercalated cells results in a group of disorders, the distal renal tubular acidoses (dRTA), whose features include metabolic acidosis accompanied by disturbances of potassium balance, urinary calcium solubility, bone physiology and growth. Mutations in the gene encoding the B-subunit of the apical pump (ATP6B1) cause dRTA accompanied by deafness. We previously localized a gene for dRTA with preserved hearing to 7q33-34 (ref. 4). We report here the identification of this gene, ATP6N1B, which encodes an 840 amino acid novel kidney-specific isoform of ATP6N1A, the 116-kD non-catalytic accessory subunit of the proton pump. Northern-blot analysis demonstrated ATP6N1B expression in kidney but not other main organs. Immunofluorescence studies in human kidney cortex revealed that ATP6N1B localizes almost exclusively to the apical surface of -intercalated cells. We screened nine dRTA kindreds with normal audiometry that linked to the ATP6N1B locus, and identified different homozygous mutations in ATP6N1B in eight. These include nonsense, deletion and splice-site changes, all of which will truncate the protein. Our findings identify a new kidney-specific proton pump 116-kD accessory subunit that is highly expressed in proton-secreting cells in the distal nephron, and illustrate its essential role in normal vectorial acid transport into the urine by the kidney.

Acidosis, Renal Tubular↗
PubMed1975

Distal renal tubular acidosis in infancy: a bicarbonate wasting state.

Three unrelated infants with apparently distal RTA were investigated. Growth retardation, polyuria, nephrocalcinosis, inappropriately high urinary pH, and marked dependence of bicarbonate excretion on urinary flow were characteristic of the distal or classic form of RTA, but the urinary loss of bicarbonate at normal serum values exceeded that usually found in children or adults with this disorder. Renal tubular function was studied during hypotonic saline diuresis in the three patients and in seven healthy control infants of similar age. Fractional delivery of sodium to the distal nephron was significantly higher in the patients than in control subjects. Sodium transport at the diluting segment was not impaired. The results support the assumption that the bicarbonate wasting was the consequence of an increased delivery of this substance to an already impaired distal nephron and thus further inhibited the distal mechanisms of net acid excretion.

Acidosis, Renal Tubular↗
PubMed2000

Band 3 mutations, renal tubular acidosis and South-East Asian ovalocytosis in Malaysia and Papua New Guinea: loss of up to 95% band 3 transport in red cells.

We describe three mutations of the red-cell anion exchangerband 3 (AE1, SLC4A1) gene associated with distalrenal tubular acidosis (dRTA) in families from Malaysia and Papua NewGuinea: Gly(701)-->Asp (G701D), Ala(858)-->Asp(A858D) and deletion of Val(850) (DeltaV850). The mutationsA858D and DeltaV850 are novel; all three mutations seem to berestricted to South-East Asian populations. South-East Asianovalocytosis (SAO), resulting from the band 3 deletion of residues400-408, occurred in many of the families but did not itselfresult in dRTA. Compound heterozygotes of each of the dRTA mutationswith SAO all had dRTA, evidence of haemolytic anaemia and abnormal red-cell properties. The A858D mutation showed dominant inheritance and therecessive DeltaV850 and G701D mutations showed a pseudo-dominantphenotype when the transport-inactive SAO allele was also present. Red-cell and Xenopus oocyte expression studies showed that theDeltaV850 and A858D mutant proteins have greatly decreased aniontransport when present as compound heterozygotes (DeltaV850/A858D,DeltaV850/SAO or A858D/SAO). Red cells with A858D/SAO had only 3% ofthe SO(4)(2-) efflux of normal cells, thelowest anion transport activity so far reported for human red cells. The results suggest dRTA might arise by a different mechanism for eachmutation. We confirm that the G701D mutant protein has an absoluterequirement for glycophorin A for movement to the cell surface. Wesuggest that the dominant A858D mutant protein is possibly mis-targetedto an inappropriate plasma membrane domain in the renal tubular cell,and that the recessive DeltaV850 mutation might give dRTA because ofits decreased anion transport activity.

Acidosis, Renal Tubular↗
PubMed1990

Persistent nephrogenic diabetes insipidus, tubular proteinuria, aminoaciduria, and parathyroid hormone resistance following longterm lithium administration.

We report a patient who developed persistent nephrogenic diabetes insipidus associated with renal tubular acidosis, renal resistance to parathyroid hormone, aminoaciduria and proximal tubule pattern proteinuria in the presence of a reduced glomerular filtration rate (19-24 ml/min). A review of the previous reports of persistent nephrogenic diabetes insipidus revealed that in all patients the glomerular filtration rate had been less than 60 ml/min at presentation. Chronic renal failure may therefore predispose to the development of persistent nephrogenic diabetes insipidus in patients receiving lithium.

Acidosis, Renal Tubular↗