Clinico-pathological correlation of severe tubulointerstitial fibrosis in glomerular diseases.

BACKGROUND: Renal histopathology is the best method available to assess chronicity ofglomerular diseases. However renal biopsy is an invasive procedure and is available only in medical schools or tertiary-care hospitals in Thailand. Clinical predictors that discriminate the chronicity index of renal pathology may be valuable for the best timing of biopsy. The authors conducted this study to identify the clinical parameters of severe fibrosis in glomerular diseases. MATERIAL AND METHOD: The authors retrospective analyzed all consecutive patients with glomerular diseases who underwent ultrasound-guided renal biopsy in Siriraj Hospital between 2008 and 2010. The patients were statified according to degree of tubulointerstitial fibrosis (IF) into mild to moderate group (IF < 50%) and severe group (IF ≥ 50%). Data of clinical and radiological parameters which relate to severe fibrosis were obtained. Formula for prediction of advanced IF was also developed by backward stepwise logistic regression analysis. The authors also validated the model by application to the patients who underwent kidney biopsy in our center between 2011 and 2012. RESULTS: Of a total 682 patients, 169 patients (24.8%) were classified as a severe IF group. In the multivariate model, higher serum creatinine, lower mean length of both kidneys and systolic blood pressure (SBP) of more than 140 mmHg were significantly related to severe IF All three factors were incorporated into apredictive model: e(x)/(1 +e(x)) while x = 1.3 + (0.6 x serum Cr in mg/dl)--(0.4 x mean length of both kidneys in cm)+(0.7 x 1 if SBP ≥ 140 mmHg or 0 if < 140 mmHg). The formula had AUROC of 0.82 and if calculated probability of fibrosis is higher than 0.37, it yields 90% specificity and 44% sensitivity for the prediction ofsevere fibrosis. When applied to 523 patients who underwent renal biopsy in 2011 and 2012, the sensitivity was 65.6% while specificity was 87.8%. CONCLUSION: High serum creatinine, presence of HT and decreased mean length of both kidneys are important clinical markers to predict renal fibrosis. The model constructed from these factors could be used in clinical practice for appropriate decision making.

Warfarin related nephropathy: the first case report in Thailand.

Warfarin is the most prescribed oral anticoagulant. Adverse renal effect from warfarin therapy are uncommon and Thailand is not acquainted. Warfarin-related nephropathy (WRN) is a newly recognized complication of warfarin treatment, especially in patients with chronic kidney disease. The authors hereby report a 56-year-old man who developed gross hematuria and severe acute kidney injury (AKI) necessitating hemodialysis, following supra-therapeutic INR level. Renal pathology revealed extensive intratubular obstruction with red blood cell casts. From the literature, there were only twelve case reports of WRN, which were confirmed by renal histopatology. Renal survival of this condition was unsatisfactory. However, our patient was dialysis-independent after vitamin K treatment and temporary warfarin discontinuation. To the best of our knowledge, this is the first case report of biopsy-proven WRN in Thailand.

Cost-Utility Analysis of Erythropoietin for Anemia Treatment in Thai End-Stage Renal Disease Patients with Hemodialysis.

OBJECTIVE: To compare the cost utility of using erythropoietin (EPO) to maintain different hemoglobin (Hb) target levels in hemodialysis patients from a societal perspective. METHODS: A Markov model was used to estimate the incremental cost and quality-adjusted life-year of five Hb levels: 9 or less, more than 9 to 10, more than 10 to 11, more than 11 to 12, and more than 12 g/dl. A systematic review of EPO treatment in hemodialysis patients was conducted to estimate transitional probabilities. Cost data were estimated on the basis of the reference price of Siriraj Hospital, the largest university hospital in Thailand. Utility scores were derived from the six-dimensional health state short form (derived from short-form 36 health survey), which were collected from 152 hemodialysis patients receiving EPO at Siriraj hospital. Probabilistic sensitivity analysis was conducted to investigate the effect of uncertain parameters. All future costs and outcomes were discounted at the rate of 3% per annum. RESULTS: The incremental cost-effectiveness ratios of Hb levels more than 9 to 10, more than 10 to 11, more than 11 to 12, and more than 12 g/dl compared with the least costly option (Hb ≤ 9 g/dl) were US $24,128.03, US $18,789.07, US $22,427.36, and US $28,022.33 per quality-adjusted life-year, respectively. From probabilistic sensitivity analysis, the hemoglobin level of more than 10 to 11 g/dl was appropriate when the willingness to pay was US $15,523.88 to US $46,610.17 and the probability of cost-effective was 29.32% to 95.94%. CONCLUSIONS: Providing EPO for a hemoglobin level of more than 10 to 11 g/dl had a cost-effectiveness higher than that of doing so for other hemoglobin levels. This finding will be put forward to the policy level to set up the EPO treatment guideline of the hospital for hemodialysis patients.

Buttonhole technique better than area puncture technique on hemostasis and pain associated with needle cannulation.

BACKGROUND: The buttonhole (constant site) arteriovenous fistulae cannulation technique, in which the inserted needle utilizes exactly the same site and the same angle every dialysis session, offers the advantage of an easier cannulation procedure, less pain associated with cannulation, and fewer complications when compared with the traditional method. OBJECTIVE: To compare buttonhole arteriovenous fistula (AVF) cannulation technique with area puncture method on the effect of hemostasis after needle withdrawal and pain during needle puncture. MATERIAL AND METHOD: The duration of hemostasis after needle withdrawal and pain during needle puncture of AVF were prospectively recorded in 21 chronic hemodialysis patients at Siriraj Hospital. The data that were collected while using area puncture with sharp needle and while using buttonhole with blunt needle were compared by using Paired t-test. RESULTS: Compared with area puncture method, the duration of hemostasis after needle withdrawal in patients using buttonhole method was significantly shorter in both arterial (4.19 +/- 1.66 mins vs. 9.12 +/- 2.36 mins, p < 0.0001) and venous site (3.92 +/- 1.37 mins vs. 9.12 +/- 2.36 mins, p < 0.0001). The pain score during needle puncture of AVF in patients using buttonhole method was also significantly less than area puncture method in both arterial (1.20 +/- 0.90 vs. 6.03 +/- 0.90, p < 0.0001) and venous site (1.38 +/- 0.75 vs. 5.88 +/- 0.82, p < 0.0001). CONCLUSION: Buttonhole AVF puncture method is a useful technique to reduce both the time for hemostasis after needle withdrawal and pain during needle puncture.

Efficacy and hemodynamic outcome of prolonged intermittent renal replacement therapy (PIRRT) in critically ill patients: a preliminary report.

BACKGROUND: Acute kidney injury (AKI) is frequently part of a multiple-organ dysfunction syndrome presenting in critically ill patients. Prolonged intermittent renal replacement therapy (PIRRT) provides the advantages of both continuous renal replacement therapy (CRRT) in term of hemodynamic stability and the cost-effectiveness of intermittent hemodialysis (IHD). This study aims to study PIRRT in the aspects of efficacy and hemodynamic outcomes. MATERIAL AND METHOD: The authors present a single-center experience accumulated over 20 months from February 2009 to September 2010 with two PIRRT techniques, called SLEDD and SLEDD-f. Eight-hour treatments were performed daily for three consecutive days. Hemodynamic parameters were recorded at different time points and blood samples were taken for urea and solute clearance before and after treatment. RESULTS: Sixty critically ill patients with AKI were randomly assigned to undergo PIRRT 33 patients received SLEDD and 27 patients received SLEDD-f. Our results demonstrate significant decrease in BUN, creatinine, serum potassium and phosphate in both PIRRT techniques. Moreover with the use of similar filters and blood flow rates, SLEDD-f was comparable with SLEDD in terms of small solute clearance and detoxification. For hemodynamic outcomes, the authors found that MAP increased after completion of the first session of PIRRT and along the three consecutive days of daily PIRRT, together with the gradual improvement of vasopressor scores. CONCLUSION: The prolonged intermittent renal replacement therapy (PIRRT) appears to be an outstanding technique for treatment of critically ill patients with AKI and it also seems to have cost effectiveness. Moreover it is suitable to a limited resource region such as Thailand.

Practical guidelines for automated peritoneal dialysis.

The development of APD technologies enables physician to customize PD treatment for optimal dialysis. Dialysis dose can be increased with APD alone or in conjunction with daytime dwells. Although there is no strong evidence of the advantage over CAPD, APD is generally recommended for patients having a high peritoneal transport, outflow problems or high intraperitoneal pressure (IPP) and those who depend on caregivers for their dialysis. The benefits of APD over CAPD depends on the problems and treatment results among dialysis centers. Before starting the APD, medical, psychosocial and financial aspects, catheter function, residual renal function (RRF), body surface area and peritoneal transport characteristic must be evaluated. The recommended starting prescription for APD is the dwell volume of 1,500 ml/m2, 2 hours/cycle, and 5 cycles/session, which will provides 10-15 L of total volume and 10 hours per session. The IPP should be monitored and kept below 18 cmH2O. NIPD is accepted for patients with significant RRF. Anuric patients usually require 15-20 L of total fill volume and may need 1-2 day-dwells of 2L icodextrin or hypertonic glucose solutions. Small solute clearances and ultrafiltration depend on the peritoneal catheter function and dialysis schedule. The clinical outcomes and small solute clearances must be monitored and adjusted accordingly to meet the weekly total Kt/V urea > or = 1.7 and in low peritoneal transporters, the weekly total CCr should be > or = 45 L/1.73 m2. The volume status must be normal. To diagnose the peritonitis in NIPD patients, 1 L of PDF should be infused and permitted to dwell for 2 hours before sending for analysis. The differential of white cell count may be more useful than the total cell counts. In Siriraj Hospital, APD patients had 1.5-3 times less peritonitis than CAPD patients and most of our anuric patients can achieve the weekly total Kt/V urea target with 10 L of NIPD.

Nephrotic syndrome in elderly patients: three years experience at Siriraj Hospital.

BACKGROUND: The population age is being high and nephotic syndrome is a common renal disease. OBJECTIVE: To find the etiology and clinical manifestations of nephrotic syndrome in the elderly patients who underwent renal biopsy at Siriraj hospital including management and outcome. MATERIAL AND METHOD: Retrospective study in 76 nephrotic patients whose age > or =50 years and underwent renal biopsy between 2005-2007. RESULTS: Seventy six nephrotic patients with age ranged from 50-84 years were analysed. Primary glomerulonephritis diseases were found more than secondary causes (5:2). The two most common glomerulonephritis were membranous GN and focal/segmental glomerulosclerosis. The etiology of common secondary GN was lupus nephtitis 11.84% following by diabetic nephropathy and amyloidosis. The patients received immunosuppressive drugs and complete response was found in 51%, partial response 10.2%, no response was 2% and no immunosuppressive therapy 36.7%. There was 1 patient died of septicaemia. CONCLUSION: Nephrotic syndrome in the elderly patients were not uncommon. The causes should be identified for prompt management and excellent outcome.

Acute kidney injury in primary nephrotic syndrome: report of nine cases in Siriraj Hospital.

Acute kidney injury is a rare but important complication of nephrotic syndrome. We demonstrated here nine patients with nephrotic syndrome and oliguric renal failure in Siriraj Hospital during 2007-2009. Renal biopsy was done in every patient. The results were focal and segmental glomerulosclerosis (FSGS) in three patients, minimal change disease in four patients and collapsing focal segmental glomerulosclerosis in two patients. Seven patients had dramatic response to corticosteroid treatment within a few weeks and had rapid recovery of renal function. The exact mechanism of idiopathic renal failure is not well understood but it might be related to reduction in ultrafiltration coefficient of the glomeruli.

Randomized trial comparing pulse calcitriol and alfacalcidol for the treatment of secondary hyperparathyroidism in haemodialysis patients.

AIM: Calcitriol and alfacalcidol are used extensively for the treatment of secondary hyperparathyroidism. Unfortunately, there is limited published data comparing the efficacy and tolerability of both active vitamin D sterols. This study was undertaken to determine whether calcitriol provides a therapeutic advantage to alfacalcidol. METHODS: This was a randomized, active controlled study. Patients with intact parathyroid hormone (iPTH) >32 pmol/L were randomized to receive orally calcitriol or alfacalcidol after each haemodialysis for up to 24 weeks. Reduction of PTH, changes of plasma albumin-corrected calcium and phosphorus were analysed. The initial dose of alfacalcidol was twice that of calcitriol. RESULTS: Sixteen patients were randomized into each group. At baseline, plasma albumin-corrected calcium, phosphorus and PTH were no different between groups. At 24 weeks, PTH changes were -50.8 ± 31.8% and -49.4 ± 32.5% from the baseline in the calcitriol and alfacalcidol groups, respectively (P = 0.91). The patients who achieved target PTH of 16-32 pmol/L were 82% in the calcitriol and 67% in the alfacalcidol group (P = 0.44). Plasma albumin-corrected calcium and phosphorus were not significantly different but showed trends toward gradually increasing from baseline in both groups (calcium, 6.0 ± 7.2% vs 10.9 ± 6.5% (P = 0.10); phosphorus, 13.0 ± 29.4% vs 16.7 ± 57.2% (P = 0.83) in calcitriol and alfacalcidol, respectively). The mean dose of calcitriol and alfacalcidol were 4.1 and 6.9 µg/week, respectively (P < 0.0001). CONCLUSION: Alfacalcidol can be used to control secondary hyperparathyroidism at doses of 1.5-2.0 times that of calcitriol. The two drugs are equally efficacious and lead to similar changes in calcium and phosphorus.

Prothrombin haplotype associated with kidney stone disease in Northeastern Thai patients.

OBJECTIVE: To evaluate genetic variations associated with kidney stone disease in Northeastern Thai patients. METHODS: Altogether, 67 single nucleotide polymorphisms (SNP) distributed within 8 candidate genes, namely TFF1, S100A8, S100A9, S100A12, AMBP, SPP1, UMOD, and F2, which encode stone inhibitor proteins, including trefoil factor 1, calgranulin (A, B, and C), bikunin, osteopontin, tamm-Horsfall protein, and prothrombin, respectively, were initially genotyped in 112 individuals each and in additional subjects to consist of 164 patients and 216 control subjects in total. RESULTS: We found that minor allele and homozygous genotype frequencies of 8 of 10 SNPs distributed within the F2 gene were significantly higher in the control group than in the patient group. Two F2 haplotypes were found to be dually associated with kidney stone risk, one (TGCCGCCGCG) with increased disease risk and the other (CGTTCCGCTA) with decreased disease risk. However, these 2 haplotypes were associated with the disease risks in only the female, not the male, group. CONCLUSIONS: The results of our study indicate that genetic variation of F2 is associated with kidney stone risk in Northeastern Thai female patients.

Molecular Approach for Distal Renal Tubular Acidosis Associated AE1 Mutations.

The molecular approaches to distal renal tubular acidosis (dRTA) associated AE1 mutations lead us to understand the genetic and pathophysiological aspects of the acidification defects. An unanticipated high value of the urine-blood (U-B) PCO(2) after NaHCO(3) loading observed in a case of dRTA and southeast Asian ovalocytosis (SAO) might be from a mistarget of the AE1 to the luminal membrane of type A intercalated cells. The mutations of the AE1 gene resulted in SAO and also affected renal acidification function. Notwithstanding, after the NH4Cl loading in 20 individuals with SAO, the acidification in the distal nephron was normal. The presence of both SAO and G701D mutations of AE1 gene would explain the abnormal urinary acidification in the patients with the compound heterozogosity. In terms of the effect of the mutations on trafficking of AE1, truncated kidney isoform (kAE1) of wild-type showed a 'dominant-positive effect' in rescuing the recessive mutant kAE1 (S773P or G701D) trafficking to the plasma membrane, in contrast with the dominant mutant kAE1 (R589H) resulting in a 'dominant-negative effect' when heterodimerized with the wild-type kAE1. It is notable that the dominant mutants kAE1 (R901X or G609R) expression in MDCK cells clearly results in aberrant surface expression with some mutant protein appearing at the apical membrane. These might result in net bicarbonate secretion and increasing U-B PCO(2) in the distal nephron. The molecular physiological and genetic approaches have permitted identification of the molecular defects, predominantly in transporter proteins, and should in turn prompt development of novel therapeutic strategies.

Evidence suggesting a genetic contribution to kidney stone in northeastern Thai population.

Genetic factor may play a role in the pathogenesis of kidney stone that is found in the northeastern (NE) Thai population. Herein, we report initial evidence suggesting genetic contribution to the disease in this population. We examined 1,034 subjects including 135 patients with kidney stone, 551 family members, and 348 villagers by radiography of kidney-ureter-bladder (KUB) and other methods, and also analyzed stones removed by surgical operations. One hundred and sixteen of 551 family members (21.05%) and 23 of the 348 villagers (6.61%) were affected with kidney stone. The relative risk (lambda(R)) of the disease among family members was 3.18. Calcium stones (whewellite, dahllite, and weddellite) were observed in about 88% of stones analyzed. Our data indicate familial aggregation of kidney stone in this population supporting that genetic factor should play some role in its pathogenesis. Genetic and genomic studies will be conducted to identify the genes associated with the disease.

Proteomic analysis of peritoneal dialysate fluid in patients with different types of peritoneal membranes.

Efficacy of peritoneal dialysis is determined by solute transport through peritoneal membranes. With the use of the peritoneal equilibration test (PET), peritoneal membranes can be classified as high (H), high average (HA), low average (LA), and low (L) transporters, based on the removal or transport rate of solutes, which are small molecules. Whether there is any difference in macromolecules (i.e., proteins) removed by different types of peritoneal membranes remains unclear. We performed a gel-based differential proteomics study of peritoneal dialysate effluents (PDE) obtained from chronic peritoneal dialysis (CPD) patients with H, HA, LA, and L transport rates (n=5 for each group; total n=20). Quantitative analysis and ANOVA with Tukey's posthoc multiple comparisons revealed five proteins whose abundance in PDE significantly differed among groups. These proteins were successfully identified by matrix-assisted laser desorption ionization quadrupole time-of-flight (MALDI-Q-TOF) mass spectrometry (MS) and tandem mass spectrometry (MS/MS) analyses, including serum albumin in a complex with myristic acid and triiodobenzoic acid, alpha1-antitrypsin, complement component C4A, immunoglobulin kappa light chain, and apolipoprotein A-I. The differences among groups in PDE levels of C4A and immunoglobulin kappa were clearly confirmed in a validation set of the other 24 patients (n=6 for each group) using ELISA. These data may lead to better understanding of the physiology of peritoneal membrane transport in CPD patients. Extending the study to a larger number of patients with subgroup analyses may yield additional information of the peritoneal dialysate proteins in association with dialysis adequacy, residual renal function, nutritional status, and risk of peritoneal infection.

An analysis of 3,555 cases of renal biopsy in Thailand.

BACKGROUND: The knowledge of the epidemiology of biopsied renal diseases provides useful information in clinical practice. There are several epidemiologic population-based studies of biopsy-proven nephropathies with detailed clinicopathologic correlations that could be different according to the country analyzed. OBJECTIVE: To identify the prevalence of primary and secondary glomerular diseases and to study the trend of the pattern changes of the glomerulopathy in Thailand. MATERIAL AND METHOD: A retrospective study of percutaneous renal biopsies during a 23-year period of 1982 to 2005 was performed. A total of 3,555 consecutive native kidney biopsies in adult patients between 12 and 84 years of age were analyzed for the prevalence and changes in the 5-year interval over the two decades. RESULTS: From the clinical trial of 3,275 patients, the ratio between primary and secondary glomerular diseases was 2:1 (2154:1121). The most common primary glomerular disease (2154 patients) were IgM nephropathy (n = 986, 45.8%) followed by IgA nephropathy (n = 386, 17.9%); membranous nephropathy (n = 341, 15.8%); diffuse endocapillary proliferative glomerulonephritis (n = 114, 5.3%) and diffuse crescentic glomerulonephritis (n = 71, 3.3%). Lupus nephritis was the most prevalent cause of secondary glomerulonephritis in the present study (n = 992, 88.5%). Examination of the 5-year interval along the study period revealed a significant increase in the prevalence of IgA nephropathy and diabetic nephropathy. Prevalence of focal and segmental glomerulosclerosis rose by five times over the last two decades in contrast to IgM nephropathy, which prevalence is decreasing. CONCLUSION: There is high prevalence of IgM nephropathy, IgA nephropathy, and lupus nephritis in Thailand which is different from other countries. It could be due to various races and altered environments. The information obtained from these results is an important contribution for the understanding of the prevalence in renal diseases in Thailand. It can be used as the baseline data for making efficient research into the appropriate and beneficial way of management in the future.

Effect of short-term folate and vitamin B supplementation on blood homocysteine level and carotid artery wall thickness in chronic hemodialysis patients.

OBJECTIVE: Hyperhomocysteinemia is an independent risk factor for atherosclerotic vascular disease in chronic hemodialysis patients. This stratified randomized controlled trial was designed to measure the effect of high dose oral vitamin B6, vitamin B12, and folic acid on homocysteine levels, and to evaluate the effect on atherosclerosis as measured by Intima-Media Thickness (IMT) of carotid arteries. MATERIAL AND METHOD: Fifty-four chronic hemodialysis patients with hyperhomocysteinemia were randomized to receive oral 15 mg folic acid, 50 mg vitamin B6, and 1 mg vitamin B12 daily (treatment group) or oral 5 mg folic acid alone (control group) for 6 months. Homocysteine level and IMT were measured in both groups. RESULTS: At 6 months, homocysteine levels in the treatment group were significantly reduced from 27.94 +/- 8.54 to 22.71 +/- 3.68 mmol/l (p = 0.009) and were not significantly increased from 26.81 +/- 7.10 to 30.82 +/- 8.76 mmol/l in control group (p = 0.08). Mean difference between both groups was statistically significant (p = 0.002). There was no significant difference of IMT of carotid arteries, however, a tendency that the treatment group would have less thickness was observed (0.69 +/- 0.29 mm and 0.62 +/- 0.16 mm, p = 0.99). CONCLUSION: Treatment of hyperhomocysteinemia in chronic hemodialysis patients with daily oral 15 mg folic acid, 50 mg vitamin B6, and 1 mg vitamin B12 for 6 months decreases homocysteine levels and tends to reduce IMT of carotid arteries. A long term study for the prevention of atherosclerosis is warranted.

Relationship between hyperhomocysteinemia and atherosclerosis in chronic hemodialysis patients.

BACKGROUND: Hyperhomocysteinemia is an independent risk factor of coronary artery heart disease (CAHD) and atherosclerosis in a normal population. However, it is still controversial in end-stage kidney disease patients who underwent long-term dialysis. Carotid intima-media thickness (IMT) is the standard non-invasive measurement of atherosclerosis. The aims of the present study were to determine the homocysteine (Hcy) level, and to evaluate its role as a risk factor of atherosclerosis in hemodialysis (HD) patients. MATERIAL AND METHOD: Clinical data and blood chemistries were assayed in 62 HD patients. Atherosclerosis was defined by clinical presentations of CAHD, cerebrovascular or peripheral vascular diseases, or carotid plaque by ultrasound. IMT was also measured by ultrasound RESULTS: Plasma Hcy level in HD patients was significantly higher in HD patients than normal controls (28.3 +/- 8.3 vs 9.7 +/- 2.9 micromol/l, p < 0.001). Older age (p < 0.001), male sex (p = 0.05), longer duration of HD (p = 0.05), and higher plasma Hcy level (p = 0.01) correlated with atherosclerosis by univariate analysis, but plasma Hcy did not show significant correlation by multivariable analysis. There was also correlation between IMT and atherosclerosis in HD patients (p < 0.001) but no correlation was observed between plasma Hcy level and lMT. CONCLUSION: Hyperhomocysteinemia is not an independent factor in the genesis of atherosclerosis in HD patients. Advanced age plays a major role of hyperhomocysteinemia and IMT is a useful marker of atherosclerosis in these patients.

Novel compound heterozygous SLC4A1 mutations in Thai patients with autosomal recessive distal renal tubular acidosis.

BACKGROUND: Mutations in the SLC4A1 gene have been found to cause either autosomal dominant (AD) or autosomal recessive (AR) distal renal tubular acidosis (dRTA). The SLC4A1 mutations causing AD dRTA were reported in white patients, whereas those associated with AR dRTA were often found in Southeast Asia. Here, the authors report additional novel SLC4A1 mutations in 3 patients with AR dRTA from 2 unrelated Thai families. METHODS: The patients and members of their families were clinically studied. Red cell morphology and sulfate influx were examined. The SLC4A1 gene was screened, analyzed, and confirmed for mutations by molecular genetic techniques. RESULTS: In the first family, the patient had dRTA, rickets, failure to thrive, nephrocalcinosis, and hypokalemic-hyperchloremic metabolic acidosis with a urine pH level of 7.00. He had novel compound heterozygous SLC4A1 G701D/S773P mutations, inherited from clinically normal heterozygous mother and father. In the second family, the patient and his sister had dRTA and Southeast Asian ovalocytosis (SAO) with different clinical severity. The patient had proximal muscle weakness, rickets, nephrocalcinosis, hypokalemia, normal anion gap metabolic acidosis, and urine pH level of 6.80. His sister was asymptomatic but the urine pH level could not be lowered to below 5.50 after a short acid load. Both siblings had compound heterozygous SLC4A1 SAO/R602H mutations. CONCLUSION: Two novel compound heterozygous SLC4A1 G701D/S773P and SAO/R602H mutations were identified in Thai patients with AR dRTA.

Kidney stone inhibitors in patients with renal stones and endemic renal tubular acidosis in northeast Thailand.

Distal renal tubular acidosis (dRTA) is generally associated with hypercalciuria, hypocitraturia, and nephrolithiasis. Our intention was to study glycosaminoglycans (GAGS) and nephrocalcin (NC), two well-known crystal growth inhibitors, in a population with endemic dRTA and nephrolithiasis in northeast (NE) Thailand. We studied 13 patients, six with dRTA and seven with nephrolithiasis with normal or undefined acidification function. Six healthy adults living in the same area as the patients and another six from the Bangkok (BKK) area were used as controls. We measured urinary pH, ammonia, calcium, citrate, magnesium, oxalate, potassium, sodium and uric acid. GAGS were determined by an Alcian blue precipitation method and were qualitated by agarose gel electrophoresis after being isolated using 5% cetyltrimethylammonium bromide at pH 6.0. NC isoforms were isolated as previously described by Nakagawa et al. Citrate was higher in BKK controls ( p<0.04). There was a striking difference among GAGS from BKK when compared with other groups (103.85+/-10.70 vs. 23.52+/-8.11 for dRTA, 22.36+/-14.98 for kidney stone patients and 14.73+/-2.87 mg/ml in controls from the NE region, ( p<0.0001). dRTA and stone-forming patients excrete proportionally more (C+D) than (A+B) NC isoforms ( p<0.05). Also, their NC showed a 100-fold weaker binding capacity of calcium oxalate monohydrate crystals. The ratio of chondroitin sulfate/heparin sulfate in GAGS was approximately 9/1. In addition to the traditional risk factors for nephrolithiasis in dRTA, GAGS and NC might play an important role in the pathogenesis of stone formation in this population.

Anion exchanger 1 mutations associated with distal renal tubular acidosis in the Thai population.

We have previously demonstrated that compound heterozygous (SAO/G701D) and homozygous (G701D/G701D) mutations of the anion exchanger 1 (AE1) gene, encoding erythroid and kidney AE1 proteins, cause autosomal recessive distal renal tubular acidosis (AR dRTA) in Thai patients. It is thus of interest to examine the prevalence of these mutations in the Thai population. The SAO and G701D mutations were examined in 844 individuals from north, northeast, central, and south Thailand. Other reported mutations including R602H, DeltaV850, and A858D were also examined in some groups of subjects. The SAO mutation was common in the southern Thai population; its heterozygote frequency was 7/206 and estimated allele frequency 1.70%. However, this mutation was not observed in populations of three other regions of Thailand. In contrast, the G701D mutation was not found in the southern population but was observed in the northern, northeastern, and central populations, with heterozygote frequencies of 1/216, 3/205, and 1/217, and estimated allele frequencies of 0.23%, 0.73%, and 0.23%, respectively. The higher allele frequency of the G701D mutation in the northeastern Thai population corresponds to our previous finding that all Thai patients with AR dRTA attributable to homozygous G701D mutation originate from this population. This suggests that the G701D allele that is observed in this region might arise in northeastern Thailand. The presence of patients with compound heterozygous SAO/G701D in southern Thailand and Malaysia and their apparently absence in northeastern Thailand indicate that the G701D allele may have migrated to the southern peninsular region where SAO is common, resulting in pathogenic allelic interaction.

A de novo R589C mutation of anion exchanger 1 causing distal renal tubular acidosis.

Anion exchanger 1 (AE1 or SLC4A1) mutations have been reported to cause distal renal tubular acidosis (dRTA), a disease characterized by impaired acid excretion in the distal nephron. We have recently demonstrated homozygous AE1 G701D mutation as a common molecular defect of autosomal recessive (AR) dRTA in a group of Thai pediatric patients. In the present work, we discovered a de novo heterozygous AE1 R589C mutation, previously documented in inherited autosomal dominant (AD) dRTA. Arginine at this position is conserved in all vertebrate AE proteins indicating its functional importance. Three different mutations at this position (R589C, R589H, and R589S) were all found in AD dRTA and a de novo R589H mutation has previously been recorded. Our report is the second de novo mutation but with a different substituted amino acid. A high prevalence of AE1 R589 mutations and the presence of at least two de novo mutations at this position lead us to propose that codon 589 (CGC) is a "mutational hotspot" of AE1. The mechanism of recurrent mutations probably involves methylation and deamination altering cytosine (C) to thymine (T) in the CpG dinucleotides.