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The Authors describe a case of renal tubular acidosis (type I or distal type) with neural deafness in a male child. The condition is inherited as an autosomal recessive trait. Addition of NaHCO3 and potassium to diet allowed normal growth without sequelae. Speech development was retarded because of the neurosensorial deafness, partially corrected by hearing aids.
Type IV renal tubular acidosis (RTA) is a syndrome of tubular dysfunction manifested clinically by persisting hyperkalemia and metabolic acidosis that occurs usually in patients with mild to moderate chronic glomerular insufficiency. The pathophysiologic characteristics include: reduced renal clearance of potassium; a reduced rate of renal bicarbonate reabsorption at normal plasma bicarbonate concentrations (the magnitude of which is insufficiently great to implicate the proximal tubule); an unimpaired ability to maintain a steep hydrogen ion concentration gradient between blood and urine during acidosis; and a reduced rate of renal net acid excretion despite highly acidic urine, due in part to reduced urinary excretion of ammonium, which in turn appears to be due in part to suppression of renal ammoniagenesis by hyperkalemia. Many patients with type IV RTA, but not all, have hyporeninemic hypoaldosteronism. The roles of mineralocorticoid deficiency and hyperkalemia in the pathogenesis of type IV RTA will be considered and the ameliorative effects of treatment with fludrocortisone, furosemide, and dietary potassium restriction reviewed.
The prognostic significance of distal renal tubular acidosis (DRTA) in the development of overt nephropathy (ON) in children with posterior urethral valves (PUV) is not clear. This condition was studied prospectively in 22 children with posterior urethral valve (PUV), with normal renal function. Prior to surgery, the children with ON had a higher incidence of bilateral reflux (P=0.006), but the difference was not significant for age at surgery (P=0.31), duration of voiding symptoms prior to surgery (P=0.30), presence of DRTA (P=0.35) and bladder abnormalities (P=0.27), with none of these factors being significant on logistic regression analysis. At the end of the follow-up, after surgery, age at surgery (P < or = 0.0001), duration of voiding symptoms prior to surgery (P < or = 0.0003), persistent DRTA (P=0.0001) and persistent bladder dysfunction (P=0.02) after surgery were significantly higher in children with ON. On univariate logistic regression analysis, age at surgery (P=0.009), duration of voiding symptoms prior to surgery (P=0.01), persistent DRTA (P=0.002) and persistent bladder abnormalities (P=0.03) after surgery were significant for ON after surgery, but on stepwise multivariate logistic regression analysis only persistent DRTA (P=0.002) turned out to be significant. We conclude that persistent DRTA after surgery can predict overt nephropathy in children with PUV after surgery.
We studied renal function in 13 patients with obstructive uropathy and hyperkalemic metabolic acidosis to characterize the pathogenesis of this disorder. Base-line fractional potassium excretion was lower in all patients than in controls with similar glomerular filtration rates. Acetazolamide was given to 11 patients but failed to increase fractional potassium excretion to normal. In five patients, impaired potassium excretion was associated with decreased ammonium excretion, a urinary pH below 5.5 (5.18 +/- 0.07, mean +/- S.E.M.), and aldosterone deficiency. In the remaining eight patients, the urinary pH did not fall below 5.5 (6.4 +/- 0.2) with acidosis, and we failed to lower the urinary pH and increase fractional potassium excretion to normal by administering a mineralocorticoid and sodium sulfate. A syndrome of hyperkalemic distal renal tubular acidosis may occur in patients with obstructive uropathy. In some patients, this syndrome results from a defect in hydrogen and potassium secretion in the distal nephron rather than from aldosterone deficiency. Obstructive uropathy should be included in the differential diagnosis of hyperkalemic acidosis and renal insufficiency.
We present a 15-year-old girl with distal renal tubular acidosis (dRTA) appearing in what is probably a very early stage of primary Sjögren's syndrome. On the basis of tests evaluating renal handling of H+, we attempt to explain the mechanism of the urine acidification disorder. The inability to decrease urinary pH during systemic acidosis, together with the normal increase of urinary carbon dioxide partial pressure (pCO2) values after sodium bicarbonate and neutral phosphate loading, suggest a gradient-type dRTA. The inability to lower urinary pH in response to furosemide, accompanied by markedly increased urinary excretion of NH4, HCO3, Na, and K, points to a collecting tubule permeability disorder with bicarbonate leak to the tubular lumen. This patient had never been exposed to amphotericin B. To our knowledge, immune-related dRTA as a result of a gradient defect with bicarbonate leak into the tubular lumen has not been described.
In a 47-year-old female patient distal renal tubular acidosis (dRTA) led to the development of osteomalacia following 13 years of the first episode of hypokalemic respiratory paralysis and 7 years of KHCO3 treatment. In spite of the musculoskeletal disability, intense bone pain and myopathy, the values of serum calcium (Ca++) and phosphorous (P) showed minimal deviation from the normal levels. The bone scintigraphy was the first indicator of the bone disease. As the disease progressed the serum level of alkaline phosphatase increased gradually and 25-hydroxyvitamin-D level decreased and bone scintigraphy showed multiple areas of increased radioisotope uptake. By that time the patient's condition deteriorated severely, she became almost unable to walk. Rocaltrol (calcitriol) therapy led to dramatic clinical improvement and the complete resolution of the laboratory values. When the alkaline therapy of dRTA does not prevent the development of osteomalacia, administration of a modern vitamin-D preparation can result complete healing of the bone disease.
Distal renal tubular acidosis (dRTA) is an inherited disease characterized by the failure of the kidneys to appropriately acidify urine and is associated with mutations in the anion exchanger (AE)1 gene. The effect of the R589H dRTA mutation on the expression of the human erythroid AE1 and the truncated kidney form (kAE1) was examined in transfected human embryonic kidney 293 cells. AE1, AE1 R589H, and kAE1 were present at the cell surface, whereas kAE1 R589H was located primarily intracellularly as shown by immunofluorescence, cell surface biotinylation, N-glycosylation, and anion transport assays. Coexpression of kAE1 R589H reduced the cell surface expression of kAE1 and AE1 by a dominant-negative effect, due to heterodimer formation. The mutant AE1 and kAE1 bound to an inhibitor affinity resin, suggesting that they were not grossly misfolded. Other mutations at R589 also prevented the formation of the cell surface form of kAE1, indicating that this conserved arginine residue is important for proper trafficking. The R589H dRTA mutation creates a severe trafficking defect in kAE1 but not in erythroid AE1.
A four-year-old Caucasian male with well-documented renal tubular acidosis, first noted in early infancy, was found to have profound hearing loss causing delayed speech development. The parents were first cousins, and three male half-sibs, each by a different father, were not affected. The findings suggest that the syndrome of renal tubular acidosis with deafness is a distinct nosologic entity that is determined by an autosomal recessive gene.
The mechanism of the renal tubular acidosis (RTA) occurring in patients with hepatic cirrhosis remains uncertain although it has been suggested that renal and intrarenal hemodynamic alterations could play a role in its pathogenesis. To verify this hypothesis, renal acidification was studied with an intravenous acid load of arginine hydrochloride in 51 patients with cirrhosis due to various causes. In 22 patients renal and intrarenal blood flow was also measured using the 133-Xe washout technique. RTA was found in 17 of 51 patients (33%) with the greatest incidence in alcoholic cirrhosis. The tubular defect did not appear related either to the degree of liver functional impairment or to the renal and intrarenal hemodynamic alterations.
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