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Fanconi's syndrome and distal (type 1) renal tubular acidosis in a patient with primary Sjögren's syndrome with monoclonal gammopathy of undetermined significance.

Tubulointerstitial nephritis is a well-recognized complication in primary Sjögrens syndrome. Fanconi's syndrome is a far less frequent complication compared with distal tubular dysfunction. We here describe a 49-year-old woman with primary Sjögren's syndrome. In 1997, she was diagnosed with primary Sjögren's syndrome with tubulointerstitial nephritis, and was then treated with oral prednisolone for the tubulointerstitial nephritis. In 2002, she was referred to our hospital because of progressive fatigue. At that time, biclonal spike on serum protein (IgG-kappa and IgA-kappa) and Bence-Jones protein in urine were found. Bone marrow aspiration showed 1.0% plasma cell infiltration. Thus, a diagnosis of monoclonal gammopathy of undetermined significance (MGUS) was made. In 2004, she was again admitted to our hospital because of mild renal dysfunction and hypokalemia. Laboratory evaluation showed inappropriate, alkaline urine in hyperchloremic metabolic acidosis and a positive urine anion gap, indicating the presence of distal (Type 1) renal tubular acidosis (RTA). The urine concentration defect was also found. Further studies revealed proximal tubular dysfunction, including renal glycosuria, generalized aminoaciduria, phosphaturia, uricosuria and proximal RTA. The kidney biopsy represented diffuse and severe tubulointerstitial nephritis with dense infiltrates of lymphocytes and IgA and K light chain-positive plasma cells. No findings of multiple myeloma or malignant lymphoma were observed. In conclusion, our patient had Sjögren's syndrome with MGUS and exhibited dysfunction of both proximal tubule (Fanconi's syndrome) and distal tubule, which may be attributed to diffuse tubulointerstitial nephritis.

Acidosis, Renal Tubular↗

Incomplete distal renal tubular acidosis in hypomagnesemia-dependent hypocalcemia.

The mechanism perpetuating hypocalcemia in the presence of hypomagnesemia is unknown. Two patients with this disorder had elevated immunoreactive serum parathyroid hormone levels and incomplete distal renal tubular acidosis. All abnormalities were corrected with magnesium replenishment. Postulated mechanisms include (1) parathyroid hormone activation in the serum or at the site of action dependent on magnesium, and (2) abnormalities in vitamin D metabolism that can be corrected by magnesium replacement.

Acidosis, Renal Tubular↗

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.

Acidosis, Renal Tubular↗

Bone disease in primary biliary cirrhosis: lack of association with distal renal tubular acidosis.

BACKGROUND AND AIMS: Primary biliary cirrhosis (PBC) might be complicated by osteoporosis, whose etiology remains unknown but seems to be multifactorial. Prevalence rates of 30% to 60% for distal renal tubular acidosis (DRTA) have been reported in PBC patients, generally as incomplete DRTA. Although it is undisputed that a reduced bone mineral density (BMD) is the expected outcome among patients who have been suffering from longstanding chronic metabolic acidosis, it is unclear if incomplete DRTA is also associated with metabolic bone disease in PBC patients. The present study was undertaken to compare the BMD of PBC patients with and without DRTA. METHODS: The BMD of 23 PBC patients (11 with DRTA and 12 without), all with normal clearance of creatinine, was assessed by dual energy radiograph absorptiometry. The diagnosis of DRTA was made if the urine pH was above 5.4 in all samples after the oral acid overload, showing tubular inability to acidify urine in the presence of test-induced systemic metabolic acidosis. RESULTS: Densitometric signs of osteoporosis were found in 82% of DRTA cases and in 83% of patients without DRTA (difference not significant). There were no significant differences in BMD measurement, T and Z scores of patients with and without DRTA. CONCLUSIONS: The present study could not support a correlation between the presence of DRTA and the bone loss observed in PBC patients.

Acidosis, Renal Tubular↗

Thyrotoxicosis and renal tubular acidosis presenting as hypokalaemic paralysis.

A 34-yr-old Chinese woman presented with hypokalaemic periodic paralysis. She had a goitre and was biochemically thyrotoxic. However, she also had urinary potassium loss with a metabolic acidosis and reduced ability to acidify her urine. The co-existence of distal renal tubular acidosis (RTA) was confirmed. There was no evidence of xerostomia or xerophthalmia, although anti-Ro antibody and rheumatoid factor were positive. Paralytic attacks did not recur after the thyrotoxicosis was controlled with radioactive iodine. Possible pathogenic mechanisms for the association of these disorders are discussed. Female patients presenting with thyrotoxic periodic paralysis (TPP) should be thoroughly investigated for possible additional precipitating factors in view of the strong male predominance of TPP, particularly when there are atypical metabolic features.

Acidosis, Renal Tubular↗

[Hypokalemic pareses secondary to renal tubular acidosis].

A 24 year old woman presented with flaccid paralysis, severe hypokalaemia and hyperchloremia, metabolic acidosis. Immunological tests and labial glandular biopsy indicated primary Sjögren's syndrome as the underlying cause of her distal renal tubular acidosis. The patient recovered after alkali and potassium substitution and was put on oral treatment with potassium citrate.

Acidosis, Renal Tubular↗

Renal tubular acidosis secondary to FK506 in living donor liver transplantation: a case report.

FK506 is an immunosuppressant that is thought to be less nephrotoxic than cyclosporine A. However, complications due to renal tubular acidosis (RTA) have recently been reported. We report a case of RTA secondary to FK506 administration in liver transplantation. A 6-month-old girl was treated with FK506 after undergoing living donor liver transplantation for fulminant hepatitis. On postoperative day 17, she demonstrated hyperkalaemia and metabolic acidosis; she was diagnosed to have hyperkalaemic distal RTA with aldosterone deficiency (type IV). Intravenous sodium bicarbonate and furosemide, and intrarectal calcium polystyrenesulfonate were administered to correct the acidosis and promote potassium secretion. Thereafter, the FK506 concentration in whole blood gradually decreased, and the hyperkalaemia and metabolic acidosis following RTA improved. RTA is one type of nephrotoxicity induced by FK506, and it is reversible in mild cases when appropriately treated. The mechanism of RTA induced by FK506 has not yet been clearly elucidated. Surgeons and physicians should therefore be aware of the potential for RTA to occur with FK506 after any organ transplantation. The treatment for acidosis and hyperkalaemia should be started as soon as RTA is diagnosed, and the dosage of FK506 should also be reduced if possible.

Acidosis, Renal Tubular↗

Osteomalacia secondary to renal tubular acidosis in a patient with primary Sjögren's syndrome.

We report a case of a 41-year-old woman whose disease manifested as osteomalacia and whose etiological investigation revealed renal tubular acidosis secondary to primary Sjögren's syndrome. Proximal tubular dysfunction was also present and was documented by increased urinary excretion of beta-2-microglobulin and retinol-binding protein. The patient showed clinical and laboratory improvement after treatment with oral potassium citrate, calcium supplements and steroids.

Acidosis, Renal Tubular↗

Osteopetrosis, renal tubular acidosis and basal ganglia calcification in three sisters.

Three adult sisters with osteopetrosis in infancy had spontaneous resolution of bone modeling defects and osteosclerosis. During adolescence, basal ganglia calcification developed in two. Renal tubular acidosis (type I) was diagnosed in each during early adulthood. The disorder was transmitted apparently as a recessive trait--the same mode of inheritance as for the "malignant" form of osteopetrosis which is usually fatal during childhood. Electron microscopy of bone suggested that osteoclasts failed to form "ruffled membranes" characteristic of active bone resorbing cells. Chronic systemic acidosis may have ameliorated the skeletal manifestations of this new syndrome.

Acidosis, Renal Tubular↗

Symptomatic renal tubular acidosis (RTA) in patients with systemic lupus erythematosus: an analysis of six cases with new association of type 4 RTA.

OBJECTIVES: We have analysed the association between different parameters of renal tubular acidosis (RTA) with clinical and laboratory parameters in patients with systemic lupus erythematosus (SLE). METHODS: Review of hospital database records between 1978 and 2003 revealed six SLE patients with RTA. Correlations and comparisons were done by Spearman rank correlation coefficient and the chi(2) test. RESULTS: Four patients had hypokalaemia (type 1 RTA) and two patients had hyperkalaemia (type 4 RTA). Three patients with type 1, but no patients with type 4 RTA, had medullary nephrocalcinosis. The majority of SLE patients with distal RTA (type 1 and type 4) had nephritis with proteinuria. No seronegative SLE was noted, and all patients were negative for anticardiolipin antibodies. There was a noticeable trend of higher serum potassium levels with increased SLE Disease Activity Index (SLEDAI; P < 0.1) and nephritic manifestation (haematuria, P < 0.1). The mean SLEDAI scores were 11.75 and 27.5 for type 1 and type 4 RTA patients, respectively. CONCLUSIONS: When present in patients with SLE, classic distal RTA (type 1) is the most common. In particular, we report here for the first time two cases of type 4 RTA in SLE patients with higher SLEDAI scores than patients with type 1 RTA. Medullary nephrocalcinosis or renal urolithiasis has not been found in our patients with type 4 RTA. Higher serum potassium levels seem to be associated with higher SLEDAI scores and more severe nephritic manifestations in patients with distal RTA.

Acidosis, Renal Tubular↗

Hypercalciuria and altered intestinal calcium absorption occurring independently of vitamin D in incomplete distal renal tubular acidosis.

Negative calcium balance and calcium nephrolithiasis are two sequelae of chronic metabolic acidosis. To establish the effects of acidosis on calcium and vitamin D metabolism, we have examined a group of nine patients with incomplete distal renal tubular acidosis. Patients were studied during a control phase and after eight months of potassium citrate treatment, 60 to 80 meq daily. Potassium citrate caused a significant decrease in urinary calcium. The fractional intestinal calcium absorption increased significantly, yet no change was observed in serum vitamin D levels. The estimated calcium balance increased significantly from -70.2 +/- 63.8 to +66.7 +/- 48.7 mg/d (P less than 0.01). Thus, potassium citrate treatment improved the estimated calcium balance by lowering urinary calcium while increasing the fractional intestinal calcium absorption. The original hypercalciuric state, its correction to normocalciuria, and the augmentation of intestinal calcium absorption seen in these patients are probably independent of vitamin D control since there was no change noted in serum 1,25-dihydroxyvitamin D levels.

Acidosis, Renal Tubular↗

Mutations in the gene encoding B1 subunit of H+-ATPase cause renal tubular acidosis with sensorineural deafness.

H+-ATPases are ubiquitous in nature; V-ATPases pump protons against an electrochemical gradient, whereas F-ATPases reverse the process, synthesizing ATP. We demonstrate here that mutations in ATP6B1, encoding the B-subunit of the apical proton pump mediating distal nephron acid secretion, cause distal renal tubular acidosis, a condition characterized by impaired renal acid secretion resulting in metabolic acidosis. Patients with ATP6B1 mutations also have sensorineural hearing loss; consistent with this finding, we demonstrate expression of ATP6B1 in cochlea and endolymphatic sac. Our data, together with the known requirement for active proton secretion to maintain proper endolymph pH, implicate ATP6B1 in endolymph pH homeostasis and in normal auditory function. ATP6B1 is the first member of the H+-ATPase gene family in which mutations are shown to cause human disease.

Acidosis, Renal Tubular↗

Localization and regulation of the ATP6V0A4 (a4) vacuolar H+-ATPase subunit defective in an inherited form of distal renal tubular acidosis.

Vacuolar-type H(+)-ATPases (V-H(+)-ATPases) are the major H(+)-secreting protein in the distal portion of the nephron and are involved in net H(+) secretion (bicarbonate generation) or H(+) reabsorption (net bicarbonate secretion). In addition, V-H(+)-ATPases are involved in HCO(3)(-) reabsorption in the proximal tubule and distal tubule. V-H(+)-ATPases consist of at least 13 subunits, the functions of which have not all been elucidated. Mutations in the accessory ATP6V0A4 (a4 isoform) subunit have recently been shown to cause an inherited form of distal renal tubular acidosis in humans. Here, the localization of this subunit in human and mouse kidney was studied and the regulation of expression and localization of this subunit in mouse kidney in response to acid-base and electrolyte intake was investigated. Reverse transcription-PCR on dissected mouse nephron segments amplified a4-specific transcripts in proximal tubule, loop of Henle, distal convoluted tubule, and cortical and medullary collecting duct. a4 protein was localized by immunohistochemistry to the apical compartment of the proximal tubule (S1/S2 segment), the loop of Henle, the intercalated cells of the distal convoluted tubule, the connecting segment, and all intercalated cells of the entire collecting duct in human and mouse kidney. All types of intercalated cells expressed a4. NH(4)Cl or NaHCO(3) loading for 24 h, 48 h, or 7 d as well as K(+) depletion for 7 and 14 d had no influence on a4 protein expression levels in either cortex or medulla as determined by Western blotting. Immunohistochemistry, however, demonstrated a subcellular redistribution of a4 in response to the different stimuli. NH(4)Cl and K(+) depletion led to a pronounced apical staining in the connecting segment, cortical collecting duct, and outer medullary collecting duct, whereas NaHCO(3) loading caused a stronger bipolar staining in the cortical collecting duct. Taken together, these results demonstrate a4 expression in the proximal tubule, loop of Henle, distal tubule, and collecting duct and suggest that under conditions in which increased V-H(+)-ATPase activity is required, a4 is regulated by trafficking but not protein expression. This may allow for the rapid adaptation of V-H(+)-ATPase activity to altered acid-base intake to achieve systemic pH homeostasis. The significance of a4 expression in the proximal tubule in the context of distal renal tubular acidosis will require further clarification.

Acid-Base Equilibrium↗

The urine-blood PCO gradient as a diagnostic index of H(+)-ATPase defect distal renal tubular acidosis.

BACKGROUND: Urine pH during acidemia and urine PCO2 upon alkalization both may be useful to indicate H+ secretion from collecting ducts. The urine anion gap has been used to detect urinary NH4+ for differential diagnosis of hyperchloremic metabolic acidosis. We have previously demonstrated that the lack of normal H(+)-ATPase may underlie secretory defect distal renal tubular acidosis (dRTA). In this study we evaluated the diagnostic value of the urine-blood (U-B) PCO2 in H(+)-ATPase defect dRTA, and compared it with that of urine pH and urine anion gap during acidemia. METHODS: In H(+)-ATPase defect dRTA, the diagnostic values of three urinary parameters were evaluated: (1) urine pH measured after acid (NH4Cl) loading; (2) urine-to-blood carbon dioxide tension gradient (U-B PCO2) during alkali (NaHCO3) loading; and (3) urine anion gap during acidemia. Seventeen patients were diagnosed as having H(+)-ATPase defect dRTA based on reduced urinary NH4+ and an absolute decrease in H(+)-ATPase immunostaining in intercalated cells on renal biopsy. Eight patients with non-dRTA renal disease served as control patients. RESULTS: Upon NaHCO3 loading, U-B PCO2 was < or =30 mm Hg in all 17 dRTA patients and >30 mm Hg in all 8 control patients. With NH4Cl loading, urine pH was >5.4 in 15 of 17 dRTA patients and < or =5.4 in 7 of 8 control patients, and the urine anion gap was >5 mmol/L in 13 of 17 dRTA patients and< or =5 mmol/L in 6 of 8 control patients. Therefore, the sensitivity and specificity of U-B PCO2 < or =30 mm Hg during NaHCO3 loading were both 100%, whereas those of urine pH >5.4 or urine anion gap >5 mmol/L during NH4Cl loading were below 90%. In control patients, the U-B PCO2 was found to be well correlated with the urinary NH4+ (r= 0.79, P < 0.05). CONCLUSION: The U-B PCO2 during NaHCO3 loading is an excellent diagnostic index of H(+)-ATPase defect dRTA.

Acidosis, Renal Tubular↗

Distal renal tubular acidosis associated with large vestibular aqueduct and sensorineural hearing loss.

CONCLUSIONS: Hearing loss and equilibrium dysfunction have different etiologies in patients with large vestibular aqueduct syndrome. We suggest that all children with distal renal tubular acidosis (dRTA) should be subjected to an equilibrium study and audiological evaluation, as well as to a CT or MRI scan. OBJECTIVE: dRTA has been described in association with sensorineural hearing loss, but there are no reported cases that have been examined in detail using audiological and equilibrium studies. We report here a case of progressive sensorineural hearing loss with a large vestibular aqueduct and dRTA, and the results of audiological and equilibrium studies. MATERIAL AND METHODS: A 31-year-old female presented with hearing loss, tinnitus and vertigo. She had been treated with oral sodium citrate, potassium citrate and potassium chloride supplementation because of dRTA since the age of 1 month. RESULTS: The pure-tone audiogram of the patient was off the scale for the right ear and showed progressive sensorineural hearing loss for the left ear. Ice-water caloric testing showed canal paresis on the left side. Temporal bone CT and inner ear MRI revealed a large vestibular aqueduct and a large endolymphatic sac on both sides.

Acidosis, Renal Tubular↗

Partial deficiency of cytochrome c oxidase with isolated proximal renal tubular acidosis and hypercalciuria.

We report the case of a 5-year-old boy with mitochondrial cytopathy due to a partial deficiency of cytochrome c oxidase who had isolated proximal renal tubular acidosis and hypercalciuria. The patient developed hypotonia and blepharoptosis and exhibited growth retardation. Biochemical examination of muscle tissue revealed a partial deficiency of cytochrome c oxidase. He was treated with an alkali, hydrochlorothiazide, and indomethacin. After treatment, metabolic acidosis and hypercalciuria improved, and the patient had a catch-up growth phase. This case emphasizes the importance of performing renal tubular functional investigations and treatment in patients with mitochondrial cytopathy, even in the absence of multiple proximal tubular dysfunction.

Acidosis, Renal Tubular↗

Vanadate causes hypokalemic distal renal tubular acidosis.

Considerable evidence supports the presence of an H(+)-K(+)-ATPase along the mammalian nephron. Inhibition of this enzyme might be expected to reduce acid excretion while increasing potassium excretion, thus causing hypokalemic distal renal tubular acidosis (RTA). In this study we administered vanadate at a dose of 5 mg/kg ip for 10 days to rats. These animals developed hypokalemic distal RTA with a blood pH of 7.22 +/- 0.01, a plasma bicarbonate of 15.2 +/- 0.6 meq/l, and a plasma potassium of 3.28 +/- 0.06 meq/l. The vanadate-treated animals had a urine pH of 6.70 +/- 0.09, a value significantly higher than NH4Cl-treated animals with the same degree of acidemia (urine pH = 5.25 +/- 0.04). When cortical collecting tubules (CCT) from these animals were microdissected and H(+)-K(+)-ATPase was measured, it was decreased by approximately 75% (P less than 0.001); but H(+)-ATPase was no different from control. In medullary collecting tubule, H(+)-K(+)-ATPase was also decreased but less than in CCT. Muscle potassium concentration in the vanadate-treated animals was significantly lower than in controls. These results demonstrate that vanadate causes hypokalemic distal RTA in association with inhibition of collecting tubule H(+)-K(+)-ATPase activity.

Acidosis↗