Urinary oxalate excretion in urolithiasis and nephrocalcinosis.

AIMS: To investigate urinary oxalate excretion in children with urolithiasis and/or nephrocalcinosis and to classify hyperoxaluria (HyOx). METHODS: A total of 106 patients were screened. In those in whom the oxalate: creatinine ratio was increased, 24 hour urinary oxalate excretion was measured. Liver biopsy and/or genomic analysis was performed if primary hyperoxaluria (PH) was suspected. Stool specimens were examined for Oxalobacter formigenes in HyOx not related to PH type 1 or 2 (PH1, PH2) and in controls. RESULTS: A total of 21 patients screened had HyOx (>0.5 mmol/24 h per 1.73 m(2)); they were classified into five groups. Eleven had PH (PH1 in nine and neither PH1 nor PH2 in two). Six had secondary HyOx: two enteric and four dietary. Four could not be classified. Seven patients had concomitant hypercalciuria. Only one of 12 patients was colonised with O formigenes compared to six of 13 controls. CONCLUSIONS: HyOx is an important risk factor for urolithiasis and nephrocalcinosis in children, and can coexist with hypercalciuria. A novel type of PH is proposed. Absence of O formigenes may contribute to HyOx not related to PH1.     

Primary hyperoxaluria type 2

Primary hyperoxaluria type 2 (PH2) is a rare disease with only 24 patients reported in the literature so far. It should be considered in any patient presenting with urolithiasis or nephrocalcinosis due to hyperoxaluria. The metabolic defect is deficiency of d-glycerate dehydrogenase/glyoxylate reductase leading to characteristic hyperoxaluria and excretion of l-glycerate, the cornerstone of diagnosis of PH 2. Although development of terminal renal failure seems to be less prevalent than in PH 1, recent reports indicate that chronic as well as terminal renal insufficiency may occur. Therefore specific therapeutic measures should aim at reduction of urinary calcium oxalate saturation by potassium citrate or pyrophosphate to reduce the incidence of nephrolithiasis and nephrocalcinosis and thus improve renal survival. Secondary complications (obstruction, urinary tract infections and pyelonephritis) must be avoided. In patients with terminal renal failure isolated renal transplantation seems to carry a high risk of disease recurrence. Conclusion PH 2 is a rare but important cause of urolithiasis and nephrocalcinosis; long-term follow up is necessary, since the renal prognosis may be worse than previously anticipated. Received: 22 November 1996 / Accepted: 17 January 1997     

Uric acid excretion in children with urolithiasis

Urinary uric acid excretion was assessed in 38 children to determine whether hyperuricuria was a risk factor in children with urolithiasis. Uric acid excretion (measured per deciliter glomerular filtration rate), and fractional excretion of uric acid were similar in 27 children with hypercalciuria and calcium oxalate urinary stones, in six children with idiopathic calcium oxalate urolithiasis, and in five with uric acid urolithiasis, of whom four were white boys and one was an Asian girl. One boy with a urate stone had cystinosis. Serum uric acid concentrations exceeded 6.0 mg/dl (360 mumol/L) in two children with hypercalciuria and in two patients with idiopathic calcium oxalate urolithiasis. None of the children with calcium urolithiasis had excessive urinary excretion of uric acid. In children with hypercalciuria, uric acid excretion did not change significantly when dietary sodium was increased from 1.0 to 5.0 gm/1.73 m2. We conclude that excessive urinary uric acid excretion is seldom an additional risk factor in children with calcium urolithiasis and that dietary sodium chloride does not have a strong influence on urinary excretion of uric acid in children with hypercalciuria.     

Three different causes of hypercalciuria

Hypercalciuria is defined as urinary calcium excretion ≥0.1?mmol/kg/24?h, and can be a result of various disease states. The most frequent clinical signs of hypercalciuria include hematuria, abdominal pain, urolithiasis, nephrocalcinosis, dysuria, enuresis, and urinary tract infection. 3 case reports of children with hypercalciuria of different origin are presented, with final diagnoses of (1)idiopathic hypercalciuria, (2)familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC), and (3)metabolic bone disease of prematurity, respectively. Assessment of hypercalciuria is essential in all children with urolithiasis and nephrocalcinosis, or demineralization of bone. It should be also a part of differential diagnostic procedure in hematuria, recurrent abdominal pain, urinary tract infection and enuresis in childhood.     

原发性高草酸尿症3型8例病例系列报告并文献复习

背景：原发性高草酸尿症（PH）是一种罕见的由于先天性肝内乙醛酸代谢异常导致的遗传性肾结石/肾钙质沉着症,既往多关注1型和2型PH,PH3的致病基因HOGA1发现较晚,报告不多。 目的：总结PH3临床表型,探讨不同种族人群的PH3热点变异。 设计：病例系列报告。 方法：纳入2015年1月至2021年12月复旦大学附属儿科医院经HOGA1基因变异确诊为PH3的连续病例。从住院病史中采集临床和生物学检测信息,在PubMed、Embase、万方数据库和中国知网数据库中检索PH3病例的中、英文文献,采集病例来源（国家）、例数、性别、起病年龄、诊断年龄、起病临床表现（尿石症、肾钙质沉着症、高钙尿症、高草酸尿症）、随访时间、肾功能（慢性肾脏病2期、3期、4~5期）、随访年龄、尿路结石转归 (活动性结石、无症状结石或结石消失)、HOGA1基因变异位点。 主要结局指标：临床表型和不同种族人群的热点变异。 结果：纳入8例PH3患儿,男7例,女1例;起病年龄中位数10月龄,诊断年龄中位数16月龄。3例以肉眼血尿起病,5例以泌尿道感染起病。影像学均提示肾结石,均无肾钙质沉着表现。3例检测了24 h尿草酸,1例提示高草酸尿症;6例检测了尿钙,5例提示高钙尿症。1例失访,7例随访中位时间25个月,肾小球滤过率均维持稳定,3例肾结石消失。8例均检出HOGA1基因变异（共10个变异位点）,其中复合杂合变异5例,纯合变异3例,经ACMG分级判定6个位点为可能致病变异,4个位点为致病变异。中英文数据库共检索到82篇文献,筛选后23篇文献中321例PH3患者进入本文分析,中国36例（包括本文8例）,欧美293例。中国和欧美PH3患者：起病表现为尿石症的比例分别为83%(30/36)和85%(195/230),肾钙质沉着症分别为3%(1/29)和8%(20/261),高草酸尿症分别为90%(26/29)和96%(66/69),差异均无统计学意义;高钙尿症分别为44%(11/25)和23%（34/150),差异有统计学意义;末次随访时肾功能：中国1例PH3患者25岁时进展至终末期肾病,欧美2例PH3患者分别在8岁和33岁进展至终末期肾病;活动性结石：中国和欧美PH3患者分别为13%(3/23)和37%(22/59),差异有统计学意义。中国PH3患者热点变异为c.834G>A (splice site)、c.834_c.834+1GG>TT (splice site)和c.769T＞G (p.C257G),分别占28%(20/72)、21%(15/72)和11%(8/72);欧美PH3患者热点变异为c.700+5G>T (splice site)和c.944_946delAGG(p.E315del),分别占40%(236/586)和12%(73/586)。 结论：PH3起病年龄和诊断年龄较早,整体预后较PH1和PH2良好,中国与欧美PH3患者HOGA1基因突变可能存在不同的热点变异位点。     

Urinary outputs of oxalate,calcium, and magnesium in children with intestinal disorders. Potential cause of renal calculi.

24-hour urinary outputs of oxalate, calcium, and magnesium have been determined in a total of 62 children aged 3 months to 17 years who fell into the following groups: (i) 16 normal controls, (ii) 3 with primary hyperoxaluria, (iii) 9 with small and/or large intestinal resections, (iv) 9 with untreated coeliac disease, (v) 5 with pancreatic dysfunction, and (vi) a miscellaneous group of 20 children with a variety of intestinal disorders. Taken as a whole, 58% of patients with intestinal disorders had hyperoxaluria, and of these 7% had urinary outputs of oxalate which fell within the range seen in primary hyperoxaluria. The proportion of children with hyperoxaluria in the different diagnostic groups was as follows: intestinal resections (78%), coeliac disease (67%), pancreatic dysfunction (80%), and miscellaneous (45%). 35% of the patients with hyperoxaluria had hypercalciuria, whereas magnesium excretion was normal in all subjects studied. In 2 patients treatment of the underlying condition was accompanied by a return of oxalate excretion to normal. These results indicate that hyperoxaluria and hypercalciuria are common in children with a variety of intestinal disorders, and that such children may be at risk of developing renal calculi without early diagnosis and treatment.     

Predisposing Factors for Nephrolithiasis and Nephrocalcinosis in Cystic Fibrosis

Objective

Cystic fibrosis (CF) is characterized by chronic pulmonary disease, insufficient pancreatic and digestive function, and abnormal sweat concentration. There is controversy about predisposing factors of nephrolithiasis and nephrocalcinosis in patients with cystic fibrosis. We assessed the results of metabolic evaluation in patients with cystic fibrosis and its correlation with nephrocalcinosis.

Methods

Forty five CF patients, mean age 47.1 months, were enrolled in the study. No one had past history of nephrolithiasis and/or nephrocalcinosis. The records were reviewed for clinical characteristics and all patients underwent metabolic evaluation including serum electrolyte measurements and spot urine analysis. Ultrasonography was performed in all patients to detect nephrocalcinosis and urolithiasis.

Findings

Nephrocalcinosis was found in 5 (11%) patients. No patient had clinical symptoms of nephrolithiasis and/or micro/macroscopic hematuria. Metabolic evaluation of the CF patients versus normal reference values showed decreased serum uric acid in 48.8%, elevated serum phosphate in 24.4%, and urine oxalate excretion in 51%. Metabolic evaluation of the nephrocalcinosis positive patients versus nephrocalcinosis negative group showed no statistical difference in serum electrolytes. The mean value of urine calcium excretion was lower in patients with nephrocalcinosis (P=0.001). Despite lack of any significant correlation, higher numerical hyperoxaluria was observed in patients with severe steatorrhea. There was no statistical correlation between steatorrhea and urine calcium as well as oxalate excretion.

Conclusion

Hypocalciuria in the nephrocalcinotic CF patients may be seen. It can be hypothesized that hypocalciuria may be due to a primary defect in renal calcium metabolism in CF patients.     

Urinary outputs of oxalate, calcium, and magnesium in children with intestinal disorders. Potential cause of renal calculi

24-hour urinary outputs of oxalate, calcium, and magnesium have been determined in a total of 62 children aged 3 months to 17 years who fell into the following groups: (i) 16 normal controls, (ii) 3 with primary hyperoxaluria, (iii) 9 with small and/or large intestinal resections, (iv) 9 with untreated coeliac disease, (v) 5 with pancreatic dysfunction, and (vi) a miscellaneous group of 20 children with a variety of intestinal disorders. Taken as a whole, 58% of patients with intestinal disorders had hyperoxaluria, and of these 7% had urinary outputs of oxalate which fell within the range seen in primary hyperoxaluria. The proportion of children with hyperoxaluria in the different diagnostic groups was as follows: intestinal resections (78%), coeliac disease (67%), pancreatic dysfunction (80%), and miscellaneous (45%). 35% of the patients with hyperoxaluria had hypercalciuria, whereas magnesium excretion was normal in all subjects studied. In 2 patients treatment of the underlying condition was accompanied by a return of oxalate excretion to normal. These results indicate that hyperoxaluria and hypercalciuria are common in children with a variety of intestinal disorders, and that such children may be at risk of developing renal calculi without early diagnosis and treatment.     

Antibiotic treatment-induced tubular dysfunction as a risk factor for renal stone formation in cystic fibrosis

OBJECTIVES: Our purpose was to characterize the decisive pathophysiologic factors that lead to renal stone formation (nephrolithiasis) in patients with cystic fibrosis (CF). METHODS: Patients with CF (n = 96) were investigated with respect to lithogenic and inhibitory factors of urolithiasis and compared with 30 healthy control patients. They were subdivided into 2 groups, 86 without renal stones and 10 with renal stones. RESULTS: All stones were exclusively composed of calcium oxalate. As a major pathogenic factor, a urinary disequilibrium between promoting and inhibitory components of stone formation, characterized mainly by hypercalciuria, hyperoxaluria, and hypocitraturia, was found in the patients with nephrolithiasis. They tended to have lower plasma phosphate concentrations and an increased urinary phosphate excretion. The citrate/calcium ratio proved to be a valuable means to discriminate patients with renal stones from control patients. Patients with stones had ingested more cotrimoxazole and ceftazidim, cumulatively, than patients without stones. There was an inverse correlation between the amounts of antibiotics ingested and the percentage of tubular phosphate reabsorption (r = -0.91, P <.0046). CONCLUSION: Renal stone formation in patients with CF is caused by a disequilibrium between promoting and inhibitory components of stone formation, which is dominated by hypercalciuria, hyperoxaluria, and hypocitraturia. Treatment with cotrimoxazole and ceftazidim, primarily, may lead to renal proximal tubular damage with an ensuing sequence of phosphate loss, increase of parathyroid hormone secretion, increased 1,25-dihydroxyvitamin D3 formation, and absorptive hypercalciuria.     

Urolithiasis and enteric hyperoxaluria in a child with steatorrhea

Malabsorptive states are frequently associated with increased urinary oxalate excretion. The authors describe a 10-year-old girl with steatorrhea, hyperoxaluria, and a renal calculus in a single functioning kidney. Successful management of steatorrhea corrected both the chronic diarrhea and hyperoxaluria. Enteric hyperoxaluria is a well-known etiology of calcium oxalate urolithiasis in adults. Pediatricians caring for children with malabsorptive conditions should be aware of the risk of urinary calculus formation as a result of increased dietary oxalate absorption.     

Clinical characteristics and metabolic abnormalities in preschool-age children with urolithiasis in southeast Anatolia

ObjectiveData on urolithiasis in preschool-age children are limited. The aim of this study was to investigate the metabolic etiology and clinical findings of preschool-age children with urolithiasis.MethodsThe medical records of 143 preschool-age children (81 boys, 62 girls, aged 2–6 years) with urolithiasis were retrospectively analyzed. Results of physical examination, serum biochemistry, and urine metabolic evaluation (including urinary citrate, oxalate, calcium, uric acid, cystine, and magnesium) were recorded.ResultsThe mean age at diagnosis was 3.7 ± 1.3 years. A family history of stone disease was found in 79.7% of patients, and 37% of parents had consanguineous marriages. The most common presenting symptoms were hematuria (33%) and urinary tract infection (UTI; 29%). Metabolic abnormalities were found in 119 (83.2%) patients, including hyperuricosuria in 24.5%, hypocitraturia in 23.8%, hyperoxaluria in 21.7%, hypercalciuria in 21.0%, cystinuria in 7.7%, and hypomagnesuria in 1.4%. Multiple metabolic abnormalities were found in 24 (16.8%) patients. Results of 28 stone analyses revealed calcium oxalate or phosphate, cystine, and uric acid in 15, nine, and four of the patients, respectively. ^99mTechnetium–dimercaptosuccinic acid renal scintigraphy revealed that 27.8% of the children with UTI had renal parenchymal scarring, with only four of them having vesicoureteral reflux.ConclusionThe most frequent metabolic abnormalities in preschool-age children with urolithiasis were hyperuricosuria and hypocitraturia. A comprehensive investigation of stone disease in children presenting with hematuria and UTI is important to prevent the development of renal parenchymal scarring.     

Clinical variants of idiopathic hypercalciuria in children

Out of five children with hypercalciuria, four had nephrocalcinosis and one recurrent bladder calculi. Two out of four patients with nephrocalcinosis (patients 1 and 2) had the "hyperprostaglandin E syndrome" and the other two (patients 3 and 4, siblings) had the Royer syndrome (osteopathy, dwarfism, secondary hyperparathyroidism). Treatment with hydrochlorothiazide is effective in patients without increased urinary excretion of prostaglandin, whereas patients with increased prostaglandin excretion respond better to indomethacin therapy.     

Stones, bones, and heredity

Genetic disorders of mineral metabolism cause urolithiasis, renal disease, and osteodystrophy. Most are rare, such that the full spectrum of clinical expression is difficult to appreciate. Diagnosis is further complicated by overlap of clinical features. Dent's disease and primary hyperoxaluria, inherited causes of calcium urolithiasis, are both associated with nephrocalcinosis and urolithiasis in early childhood and renal failure that can occur at any age but is seen more often in adulthood. Bone disease is an inconsistent feature of each. Dent's disease is caused by mutations of the CLCN-5 gene with impaired kidney-specific CLC-5 chloride channel expression in the proximal tubule, thick ascending limb of Henle, and the collecting ducts. Resulting hypercalciuria and proximal tubule dysfunction, including phosphate wasting, are primarily responsible for the clinical manifestations. Low-molecular-weight proteinuria is characteristic. Definitive diagnosis is made by DNA mutation analysis. Primary hyperoxaluria, type I, is due to mutations of the AGXT gene leading to deficient hepatic alanine–glyoxylate aminotransferase activity. Marked overproduction of oxalate by hepatic cells results in the hyperoxaluria responsible for clinical features. Definitive diagnosis is by liver biopsy with measurement of enzyme activity, with DNA mutation analysis used increasingly as mutations and their frequency are defined.

Conclusion

These disorders of calcium urolithiasis illustrate the value of molecular medicine for diagnosis and the promise it provides for innovative and more effective future treatments.     

Renal calcium handling in cystic fibrosis: lack of evidence for a primary renal defect.

Because cystic fibrosis (CF) epithelia have ion transport abnormalities that may in part be regulated by intracellular calcium metabolism, and the kidney is actively involved in both ion transport and calcium homeostasis, we have investigated renal calcium handling in CF. Twenty-four-hour urine collections were analyzed in 34 CF patients (age 5 to 35 years) and kidney ultrasound studies were performed in 17 CF patients (age 6 months to 23 years). Renal histologic findings at postmortem examination of 14 CF patients (age 4 months to 23 years) were compared with those of 12 patients (age 11 months to 17 years) with other chronic illnesses (6 congenital heart disease, 6 malignancy). In 30 of the 34 CF patients urinary calcium excretion was normal (less than 4 mg (0.1 mmol)/kg/24 hr). Four CF patients had hypercalciuria (calcium excretion 4.4 to 8.8 mg (0.11 to 0.22 mmol)/kg/24 hr). However, these patients had other possible explanations for hypercalciuria, such as immobilization (n = 2), increased dietary sodium load (n = 1), and glucocorticoid therapy (n = 1). None of the 17 patients examined by renal ultrasonography had nephrocalcinosis. Five CF patients had histologic evidence of sparse nephrocalcinosis at autopsy. However, 6 of 12 autopsy kidney specimens from patients with other chronic illnesses and similar preterminal events also showed nephrocalcinosis. The hypercalciuria and nephrocalcinosis in CF and other chronic debilitating diseases may be explained by factors known to affect calcium handling. Our evidence does not support a primary renal defect as the basis of hypercalciuria and nephrocalcinosis in CF.     

Long-term results of pre-emptive liver transplantation in primary hyperoxaluria type 1

In primary hyperoxaluria type 1 (PH 1), deficiency or mistargeting of hepatic alanine glyoxylate aminotransferase (AGT) results in over-production of oxalate and hyperoxaluria, leading to nephrocalcinosis and development of end-stage renal disease (ESRD) in the majority of patients. Renal transplantation (Tx) alone carries a high risk of disease recurrence as the metabolic defect is not cured. Therefore, combined liver/kidney Tx is recommended for patients with ESRD. An alternative approach is to cure PH 1 by pre-emptive isolated liver Tx (PLTx) before ESRD has occurred, but this approach has been carried out only occasionally and there are no uniformly accepted recommendations concerning the timing of this procedure. We report follow-up 3-5.7 yr after performing successful PLTx in four children (at the age of 3-9 yrs) with PH 1 prior to the occurrence of ESRD (glomerular filtration rate [GFR] range 27-98 mL/min/1.73 m2). There was no mortality or long-term morbidity associated with the Tx procedure. Plasma and urinary oxalate levels normalized rapidly within 4 weeks, and renal function did not deteriorate under immunosuppression, even in one patient with advanced chronic renal failure (GFR 27 mL/min/1.73 m2) who showed a stable course for more than 5.7 yrs. Although treatment must be individualized in this severe metabolic disorder, and PLTx has to be regarded as an invasive procedure, we consider that PLTx should be offered and considered early in the course of PH 1. PLTx cures the metabolic defect in PH 1 and can help to prevent, or at least delay, the progression to ESRD and systemic oxalosis.     

Hypercalciuria with Bartter syndrome: evidence for an abnormality of vitamin D metabolism

Some children with Bartter syndrome have hypercalciuria. To determine the mechanism for this phenomenon, we studied tubular function and calcium metabolism in six such children. All patients had hypokalemic alkalosis, normotension, hyperreninemia, growth retardation, low fractional distal chloride reabsorption (4/5), and elevated urinary prostaglandin E2 excretion (5/6). In addition, all had hypercalciuria (urinary calcium 6.5 to 25.0 mg/kg/day), with evidence of nephrocalcinosis in five. None, however, had evidence of rickets or hyperparathyroidism. There was a marked elevation in the serum concentration of 1,25-dihydroxyvitamin D in all, and four patients had a response to oral calcium loading suggestive of absorptive hypercalciuria. Five children have had long-term therapy with indomethacin. They have had improvement in hypokalemia and reduced urinary prostaglandin E2 excretion as well as reductions in the serum concentration of 1,25-dihydroxyvitamin D and in urinary calcium excretion. These data suggest that hypercalciuria in some children with Bartter syndrome is associated with an excess of 1,25-dihydroxyvitamin D. The improvement in hypercalciuria with prostaglandin synthesis inhibition may result in part from correction of this vitamin D abnormality.     

Stones, bones, and heredity

Genetic disorders of mineral metabolism cause urolithiasis, renal disease, and osteodystrophy. Most are rare, such that the full spectrum of clinical expression is difficult to appreciate. Diagnosis is further complicated by overlap of clinical features. Dent's disease and primary hyperoxaluria, inherited causes of calcium urolithiasis, are both associated with nephrocalcinosis and urolithiasis in early childhood and renal failure that can occur at any age but is seen more often in adulthood. Bone disease is an inconsistent feature of each. Dent's disease is caused by mutations of the CLCN-5 gene with impaired kidney-specific CLC-5 chloride channel expression in the proximal tubule, thick ascending limb of Henle, and the collecting ducts. Resulting hypercalciuria and proximal tubule dysfunction, including phosphate wasting, are primarily responsible for the clinical manifestations. Low-molecular-weight proteinuria is characteristic. Definitive diagnosis is made by DNA mutation analysis. Primary hyperoxaluria, type I, is due to mutations of the AGXT gene leading to deficient hepatic alanine-glyoxylate aminotransferase activity. Marked overproduction of oxalate by hepatic cells results in the hyperoxaluria responsible for clinical features. Definitive diagnosis is by liver biopsy with measurement of enzyme activity, with DNA mutation analysis used increasingly as mutations and their frequency are defined.These disorders of calcium urolithiasis illustrate the value of molecular medicine for diagnosis and the promise it provides for innovative and more effective future treatments.     

Low-dose thiazide diuretics in children with idiopathic renal hypercalciuria

Aim: To evaluate the therapeutic effect of hydrochlorothiazide in idiopathic renal hypercalciuria. Methods: We retrospectively analysed the data of 28 children (6.0 ± 4.1 years, M:F = 19:9) diagnosed as having idiopathic renal hypercalciuria from the years 1991 to 2008. The dose of hydrochlorothiazide was initially 0.5 mg/kg/day and gradually increased to achieve the appropriate hypocalciuric effect (urinary calcium/creatinine <0.2 mg/mg) in some unresponsive patients. Results: Twenty‐two patients (79%) had gross haematuria, 6 (21%) microscopic haematuria, 2 left flank pain, 6 (21%) urolithiasis and 9 (32%) urinary tract infection at the diagnosis of hypercalciuria. The low doses (0.5 mg/kg/day) of hydrochlorothiazide reduced urinary calcium excretion in 25 patients (89%) and 3 (11%) required the increased doses (1–2 mg/kg/day). Haematuria and urolithiasis gradually resolved in accordance with the improvement of hypercalciuria. Nineteen patients (68%) maintaining hypocalciuria during hydrochlorothiazide therapy were discontinued after 12.5 ± 5.3 months of treatment. Eleven of the 19 patients maintained normocalciuria, while 8 showed increased urinary calcium excretion at 2.9 ± 2.3 months after treatment was stopped, requiring thiazide retreatment. Conclusion: Our results suggest that low dose (0.5 mg/kg/day) of hydrochlorothiazide may be safe and effective in controlling renal hypercalciuria in children.     

Decreased urinary citrate excretion in type 1a glycogen storage disease

OBJECTIVES: To quantify urinary citrate and calcium excretion and systemic acid-base status in patients with type 1a glycogen storage disease (GSD1a) and to investigate their relationship to renal complications. STUDY DESIGN: Fifteen patients (7 male and 8 female; age range, 3--28 years) were studied during annual evaluations of metabolic control. All were treated with intermittent doses of uncooked cornstarch. Hourly blood sampling and a 24-hour urine collection were obtained while subjects followed their usual home dietary regimen. RESULTS: All but the youngest subject had low levels of citrate excretion (mean 2.4 +/- 1.8 mg/kg/d; 129 +/- 21 mg citrate/g creatinine). Normally, urinary citrate excretion increases with age; however, in patients with GSD1a, a strong inverse exponential relationship was found between age and citrate excretion (r = -0.84, P <.0001). Urinary citrate excretion was unrelated to markers of metabolic control. Hypercalciuria occurred in 9 of 15 patients (mean urinary calcium/creatinine ratio, 0.27 +/- 0.15) and was also inversely correlated with age (r = -0.62, P =.001). CONCLUSIONS: Hypocitraturia that worsens with age occurs in metabolically compensated patients with GSD1a. The combination of low citrate excretion and hypercalciuria appears to be important in the pathogenesis of nephrocalcinosis and nephrolithiasis. Citrate supplementation may be beneficial in preventing or ameliorating nephrocalcinosis and the development of urinary calculi in GSD1a.     

A potential pathogenic role of oxalate in autism

BackgroundAlthough autistic spectrum disorders (ASD) are a strongly genetic condition certain metabolic disturbances may contribute to clinical features. Metabolism of oxalate in children with ASD has not yet been studied.AimThe objective was to determine oxalate levels in plasma and urine in autistic children in relation to other urinary parameters.MethodIn this cross-sectional study, plasma oxalate (using enzymatic method with oxalate oxidase) and spontaneous urinary calcium oxalate (CaOx) crystallization (based on the Bonn-Risk-Index, BRI) were determined in 36 children and adolescents with ASD (26 boys, 10 girls) aged 2–18 years and compared with 60 healthy non-autistic children matched by age, gender and anthropometric traits.ResultsChildren with ASD demonstrated 3-fold greater plasma oxalate levels [5.60 (5th–95th percentile: 3.47–7.51)] compared with reference [(1.84 (5th–95th percentile: 0.50–4.70) μmol/L (p < 0.05)] and 2.5-fold greater urinary oxalate concentrations (p < 0.05). No differences between the two groups were found in urinary pH, citraturia, calciuria or adjusted CaOx crystallization rates based on BRI. Despite significant hyperoxaluria no evidence of kidney stone disease or lithogenic risk was observed in these individuals.ConclusionsHyperoxalemia and hyperoxaluria may be involved in the pathogenesis of ASD in children. Whether this is a result of impaired renal excretion or an extensive intestinal absorption, or both, or whether Ox may cross the blood brain barrier and disturb CNS function in the autistic children remains unclear. This appears to be the first report of plasma and urinary oxalate in childhood autism.