Cases reported "Acidosis, Renal Tubular"

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1/33. hyperkalemia unresponsive to massive doses of aldosterone in a patient with renal tubular acidosis.

    In a 53-year-old male patient aldosterone-refractory hyperkalemia was associated with renal tubular acidosis (RTA) due to chronic interstitial nephritis accompanied by peritubular hyaline deposits in the distal nephron. The hyperkalemia was not caused by an adrenal disorder or acidosis and could not be abolished by diuretics, cortisone, longacting synthetic ACTH, excessive doses of DOCA and aldosterone. The results of our experimental studies carried out on the hyperkalemic RTA patient as well as on various control subjects and patients suggested the presence of a specific defect in renal K excretion associated with a decreased aldosterone responsiveness of the renal tubules presumably due to the peritubular pathology.
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2/33. Renal tubular acidosis and vasculitis associated with IgE deposits in the kidney and small vessels.

    We report a woman with a history of allergies, polyuria, polydipsia, proteinuria, renal loss of electrolytes, renal tubular acidosis, nephrocalcinosis, and palpable purpura. A proximal defect was excluded by a normal bicarbonate reabsorption curve, and a distal tubular defect was shown because urine pH did not decrease to less than 6.4 despite ammonium chloride-induced systemic acidosis. Moreover, furosemide failed to improve urinary acidification. urine-to-blood PCO(2) gradient was less than 14 mm Hg, although the urine bicarbonate level reached values as high as 89 mEq/L. Combining bicarbonate and neutral phosphate infusions increased the urine-to-blood PCO(2) gradient to only 20 mm Hg. These subnormal PCO(2) gradient values point to proton-pump dysfunction in the collecting tubule. Histological evidence of tubulointerstitial disease accompanied the tubular defects. The striking histological feature was the presence of immunoglobulin e (IgE) deposits in glomeruli, tubuli, and vessels. Concurrent with these findings, she had high serum IgE titers and CD23 levels. IgE antibodies from her serum were reactive against human renal tubuli, with binding to two regions that matched two different proteins present in cortex and medulla. One of these proteins corresponded to carbonic anhydrase ii (31 kd); the second, to an unidentified protein that seems attached to cell membranes. We suggest that these IgE antibodies could have had a pathogenic role in this patient's glomerular, tubular, and small-vessel disease.
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3/33. Genetic and long-term data on a patient with permanent isolated proximal renal tubular acidosis.

    A 12-year-old girl presented with permanent isolated proximal renal tubular acidosis (pRTA), glaucoma, band keratopathy, mild cataract and short stature. Severe metabolic acidosis was caused by the impairment of bicarbonate reabsorption in the proximal tubules and alkali therapy improved her acidaemia. A homozygous G to A transition at nucleotide 1,678 in the basolateral kidney type Na /HCO3- (kNBC) cotransporter gene SLC4A4, which is critical in HCO3- resorption in renal proximal tubules, was identified. Her height and height velocity (HV) were very low (-4.0 SD and -4.4 SD, respectively) before alkali treatment, but both improved after initiating alkali therapy at the age of 2 years and 3 months. The patient's body height and HV were 131.5 cm (-2.7 SD) and 4.0 cm (-2.0 SD), respectively at the age of 12 years. CONCLUSION: This case demonstrates that early administration of alkali therapy and sustained correction of acidosis, even if inadequate to correct the metabolic acidosis, can markedly improves growth in permanent isolated proximal renal tubular acidosis.
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4/33. bone marrow transplantation corrects osteopetrosis in the carbonic anhydrase ii deficiency syndrome.

    carbonic anhydrase ii (CAII), found in renal tubules, brain, and osteoclasts, is critical in acid-base homeostasis and bone remodeling. Deficiency of CAII gives rise to a syndrome of osteopetrosis, renal tubular acidosis (RTA), and cerebral calcification with associated developmental delay. It is inherited in an autosomal recessive fashion and found most frequently in the mediterranean region and the middle east. We report 2 related Irish families with clinically severe CAII deficiency in whom the gene mutation has been fully elucidated. Two children, one from each family, have undergone allogeneic bone marrow transplantation because of severe progressive visual and hearing loss. The older 2 children had already developed cerebral calcification and marked visual loss at the time of diagnosis and were treated symptomatically. Post-transplantation evaluation at 2 and 3 years demonstrates histologic and radiologic resolution of their osteopetrosis with stabilization of hearing and vision. Both children remain developmentally delayed and continue to have RTA, and the older child has now developed cerebral calcification. Allogeneic bone marrow stem cell replacement cures the osteoclast component of CAII deficiency and retards the development of cerebral calcification, but it appears to have little or no effect on the renal lesions. (Blood. 2001;97:1947-1950)
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5/33. Urate nephropathy following chronic ileostomy acidosis.

    Normal renal function and normal urinalysis results in an 81-year-old man deteriorated over a 6-month period following an ileostomy, associated with metabolic acidosis, persistent aciduria, proteinuria, and a urinary sediment that showed numerous red blood cells, granular casts, and 'reactive' epithelial cells with intracellular uric acid (UA) crystals. These also formed extensive UA casts. Oral sodium bicarbonate therapy completely reversed all of the abnormalities. Renal biopsy, while it failed to demonstrate significant tubular obstruction, showed evidence of extensive epithelial cell injury. It is suggested that intestinal losses of bicarbonate resulted in persistent excretion of an acidic urine which promoted UA crystal formation within renal tubules and in epithelial cells which then caused cellular injury and the release of cytokines, leading to an altered regulation of the renal blood flow. The importance of microscopic techniques in the diagnosis is stressed along with the significance for managing both acute and chronic renal failure.
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6/33. The syndrome of renal tubular acidosis with nerve deafness.

    Two brothers with renal tubular acidosis and nerve deafness are described. Studies of the physiopathological characteristics of the renal acidification defect show that the defect is limited to the distal tubule. Renal tubular acidosis with nerve deafness is a distinct nosologic entity that is determined by an autosomal recessive trait.
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7/33. Renal potassium wasting in distal renal tubular acidosis: role of aldosterone.

    The pathogenesis of renal potassium wasting and hypokalemia in classic renal tubular acidosis (type 1 RTA) remains uncertain. The prevailing theory is that K( )-Na exchange is stimulated due to an inability of the distal tubule to establish a normal steep lumen-peritubular H gradient. We encountered a 42-year-old woman with type 1 RTA associated with sjogren's syndrome, in whom renal potassium wasting and hypokalemia persisted despite sustained correction of systemic acidosis with alkali therapy and increased intake of potassium. In addition, plasma renin activity was markedly increased and the serum aldosterone level was upper-normal despite the hypokalemia. Increased intake of sodium resulted in suppression on the serum aldosterone and correction of renal potassium wasting and hypokalemia. This case shows that secondary hyperaldosteronism, possibly due to an impairment of sodium conservation in the distal tubule, may contribute to the loss of potassium from the distal tubule even after the correction of acidosis.
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8/33. Renal proximal tubular dysfunction and paroxysmal nocturnal hemoglobinuria.

    A patient with paroxysmal nocturnal hemoglobinuria, who required many blood transfusions for hemolytic episodes, had a persistent hyperchloremic metabolic acidosis. Bicarbonate infusion demonstrated a large fractional excretion of bicarbonate (28.6 per cent at a plasma bicarbonate level of 23 meq/liter) which was consistent with proximal renal tubular acidosis. Generalized aminoaciduria and decreased tubular reabsorption of phosphate were also present. Marked deposition of iron in renal proximal tubules was associated with these functional abnormalities. We believe that, as systemic acidosis can promote hemolysis in patients with paroxysmal nocturnal hemoglobinuria, hemolysis can lead, by way of iron deposition in renal tubules, to further acidosis. This cycle should be interrupted with appropriate doses of bicarbonate.
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9/33. Absence of H( )-ATPase in cortical collecting tubules of a patient with sjogren's syndrome and distal renal tubular acidosis.

    Distal urinary acidification abnormalities may arise from transepithelial voltage defects, permeability defects, or proton-secretory defects, but tests to determine the cellular mechanisms underlying secretory abnormalities have not previously been reported. A patient with sjogren's syndrome and distal renal tubular acidosis due to a secretory defect is described, whose kidney biopsy was examined by fluorescent immunocytochemistry with an antibody to the M(r) 31,000 subunit of the mammalian kidney vacuolar H( )-ATPase and was compared with normal human kidney. Staining with the anti-H( )-ATPase antibody in normal human kidney was detected in the brush border microvilli and subvillar invaginations of the proximal tubule and in intercalated cells in the collecting duct. A biopsy sample from the patient was devoid of any anti-H -ATPase staining in the intercalated cells. Staining was also absent from the proximal tubule brush border microvilli but was present in the subvillar invaginations. Although autoantibodies to normal human kidney membrane proteins were detected in the serum by immunoblot analysis, no immunocytochemical evidence for anti-intercalated cell autoantibodies was observed in the patient's serum. This report demonstrates that the basis for the proton secretory defect in some patients with distal renal tubular acidosis is likely the absence of H( )-ATPase in the intercalated cells. It also illustrates the potential diagnostic utility of anti-H( )-ATPase antibodies in the classification of distal renal tubular acidoses.
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10/33. A novel missense mutation in the sodium bicarbonate cotransporter (NBCe1/SLC4A4) causes proximal tubular acidosis and glaucoma through ion transport defects.

    In humans and terrestrial vertebrates, the kidney controls systemic pH in part by absorbing filtered bicarbonate in the proximal tubule via an electrogenic Na /HCO3- cotransporter (NBCe1/SLC4A4). Recently, human genetics revealed that NBCe1 is the major renal contributor to this process. Homozygous point mutations in NBCe1 cause proximal renal tubular acidosis (pRTA), glaucoma, and cataracts (Igarashi, T., Inatomi, J., Sekine, T., Cha, S. H., Kanai, Y., Kunimi, M., Tsukamoto, K., Satoh, H., Shimadzu, M., Tozawa, F., Mori, T., Shiobara, M., Seki, G., and Endou, H. (1999) Nat. Genet. 23, 264-266). We have identified and functionally characterized a novel, homozygous, missense mutation (S427L) in NBCe1, also resulting in pRTA and similar eye defects without mental retardation. To understand the pathophysiology of the syndrome, we expressed wild-type (WT) NBCe1 and S427L-NBCe1 in xenopus oocytes. Function was evaluated by measuring intracellular pH (HCO3- transport) and membrane currents using microelectrodes. HCO3- -elicited currents for S427L were approximately 10% of WT NBCe1, and CO2-induced acidification was approximately 4-fold faster. Na -dependent HCO3- transport (currents and acidification) was also approximately 10% of WT. Current-voltage (I-V) analysis reveals that S427L has no reversal potential in HCO3-, indicating that under physiological ion gradient conditions, NaHCO3 could not move out of cells as is needed for renal HCO3- absorption and ocular pressure homeostasis. I-V analysis without Na further shows that the S427L-mediated NaHCO3 efflux mode is depressed or absent. These experiments reveal that voltage- and Na -dependent transport by S427L-hkNBCe1 is unfavorably altered, thereby causing both insufficient HCO3- absorption by the kidney (proximal RTA) and inappropriate anterior chamber fluid transport (glaucoma).
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