Primary hyperoxaluria type 1

Optimizing Screening Performance for the Risk of Hyperoxaluria and Urolithiasis Using the Urinary Oxalate/Creatinine Ratio: A Retrospective Analysis

Background and objective

The risk of chronic kidney disease (CKD) and nephrolithiasis increases with higher levels of oxalate excretion in 24-h urine, warranting monitoring in specific populations, especially after malabsorptive bariatric surgery. However, implementation of systematic 24-h urine collection is challenging, so there is a need for alternative screening methods.

Methods

Using retrospective data from patients evaluated for the risk of urolithiasis, we assessed different thresholds for the urinary oxalate/creatinine (UOx/Creat) ratio to optimize the screening performance for hyperoxaluria diagnosis and urolithiasis risk using lithogenic risk surrogates.

Key findings and limitations

Among 1264 patients referred for urolithiasis, 38% were excluded because urine collection was considered incomplete. The remaining 786 individuals were included in our analysis, of whom 16% exhibited hyperoxaluria. A UOx/Creat screening threshold between 35 and 45 μmol/mmol demonstrated good performance, depending on the clinical weighting for false-negative versus true-positive results and the cost/benefit ratio.

Conclusions and clinical implications

The UOx/Creat ratio is a promising tool in screening for hyperoxaluria-related complications. However, future research is needed to validate its performance and address the limitations identified to confirm its clinical relevance and effectiveness.

Patient summary

Our study shows that a simple test to measure the ratio of oxalate to creatinine in urine can help in identifying people at risk of kidney stones, especially for patients who have had weight-loss surgery. The test showed good screening performance, but more research is needed to confirm our findings.

Application of four pricing models for orphan medicines: a case study for lumasiran

BACKGROUND

The combination of high prices and uncertain effectiveness is a growing challenge in the field of orphan medicines, hampering health technology assessments. Hence, new methods for establishing price benchmarks might be necessary to support reimbursement negotiations. In this study, we applied several pricing models containing cost-based elements to the case of lumasiran for treating primary hyperoxaluria type 1.

METHODS

Price ranges were calculated by estimating minimum and maximum scenarios for four pricing models: Novel Cancer Pricing Model (NCP-model), AIM Model for Innovative Medicines (AIM-model), Discounted Cash Flow model (DCF-model), and the Real-Option Rate Of Return model (ROROR-model). Data was gathered from disease registries, scientific literature, Security and Exchange Committee filings, and expert opinion. A sensitivity analysis was performed to assess the parameters with the largest influence.

RESULTS

Outcomes resulting from the NCP-model ranged between €87,000 and €224,000 per patient per year, between €33,000 and €340,000 for the AIM-model, between €182,000 and €748,000 for the DCF-model, and between €81,000 and €273,000 for the ROROR-model.

CONCLUSION

Outcomes of the four pricing models show wide and heterogeneous price ranges. The DCF-model might be most compatible with the case of lumasiran, due to inclusion of parameters for prevalence, incidence, prescription restrictions and cost of capital. The minimum DCF price could serve as a starting point for pricing and reimbursement negotiations. Uncertainties can be solved by more transparency on input variables.

Primary Hyperoxaluria Type 1 (PH1) Presenting With End-Stage Kidney Disease and Cutaneous Manifestations in Adulthood: A Case Report

Rationale:

Primary hyperoxaluria (PH) is a rare autosomal recessive disorder more commonly diagnosed in children or adolescents. Owing to its rarity and heterogeneous phenotype, it is often underrecognized, resulting in delayed diagnosis, including diagnosis after end-stage kidney disease (ESKD) has occurred or recurrence after kidney-only transplantation.

Case Presentation:

A 40-year-old Caucasian Canadian woman with a history of recurrent nephrolithiasis since age 19 presented with ESKD and cutaneous symptoms. She had no known prior kidney disease and no family history of kidney disease or nephrolithiasis.

Diagnosis:

A diagnosis of primary hyperoxaluria type 1 (PH1) due to homozygous splice donor mutation (AGXT c.680+1G>A) was made with kidney and cutaneous pathology demonstrating calcium oxalate deposition and ultrasound suggestive of nephrocalcinosis.

Interventions:

She was initiated on frequent, high-efficiency, high-flux conventional hemodialysis and oral pyridoxine. Lumasiran was added 11 months later, after she developed bilateral swan-neck deformities.

Outcomes:

After 14 months of high-intensity dialysis and 3 months of lumasiran, there have been no signs of renal recovery, and extra-renal involvement has increased with progressive swan-neck deformities, reduced cardiac systolic function, and pulmonary hypertension. The patient has been waitlisted for kidney-liver transplantation.

Teaching Points:

This case report describes an adult presentation of PH1. The case highlights the importance of timely workup of metabolic causes of recurrent nephrolithiasis or nephrocalcinosis in adults which can be a presenting sign of PH and genetic testing for PH to facilitate early diagnosis and treatment especially in the era of novel therapeutics that may alter disease course and outcomes. The case also demonstrates the value of testing for PH in adults presenting with unexplained ESKD and a history of recurrent nephrolithiasis or nephrocalcinosis due to implications for organ transplantation strategy and presymptomatic family screening.

Phase 1/2 Study of Lumasiran for Treatment of Primary Hyperoxaluria Type 1: A Placebo-Controlled Randomized Clinical Trial

BACKGROUND AND OBJECTIVES

In the rare disease primary hyperoxaluria type 1, overproduction of oxalate by the liver causes kidney stones, nephrocalcinosis, kidney failure, and systemic oxalosis. Lumasiran, an RNA interference therapeutic, suppresses glycolate oxidase, reducing hepatic oxalate production. The objective of this first-in-human, randomized, placebo-controlled trial was to evaluate the safety, pharmacokinetic, and pharmacodynamic profiles of lumasiran in healthy participants and patients with primary hyperoxaluria type 1.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This phase 1/2 study was conducted in two parts. In part A, healthy adults randomized 3:1 received a single subcutaneous dose of lumasiran or placebo in ascending dose groups (0.3-6 mg/kg). In part B, patients with primary hyperoxaluria type 1 randomized 3:1 received up to three doses of lumasiran or placebo in cohorts of 1 or 3 mg/kg monthly or 3 mg/kg quarterly. Patients initially assigned to placebo crossed over to lumasiran on day 85. The primary outcome was incidence of adverse events. Secondary outcomes included pharmacokinetic and pharmacodynamic parameters, including measures of oxalate in patients with primary hyperoxaluria type 1. Data were analyzed using descriptive statistics.

RESULTS

Thirty-two healthy participants and 20 adult and pediatric patients with primary hyperoxaluria type 1 were enrolled. Lumasiran had an acceptable safety profile, with no serious adverse events or study discontinuations attributed to treatment. In part A, increases in mean plasma glycolate concentration, a measure of target engagement, were observed in healthy participants. In part B, patients with primary hyperoxaluria type 1 had a mean maximal reduction from baseline of 75% across dosing cohorts in 24-hour urinary oxalate excretion. All patients achieved urinary oxalate levels ≤1.5 times the upper limit of normal.

CONCLUSIONS

Lumasiran had an acceptable safety profile and reduced urinary oxalate excretion in all patients with primary hyperoxaluria type 1 to near-normal levels.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Study of Lumasiran in Healthy Adults and Patients with Primary Hyperoxaluria Type 1, NCT02706886.

Multiple Pathways for Pathological Calcification in the Human Body

Biomineralization of skeletal components (e.g., bone and teeth) is generally accepted to occur under strict cellular regulation, leading to mineral-organic composites with hierarchical structures and properties optimized for their designated function. Such cellular regulation includes promoting mineralization at desired sites as well as inhibiting mineralization in soft tissues and other undesirable locations. In contrast, pathological mineralization, with potentially harmful health effects, can occur as a result of tissue or metabolic abnormalities, disease, or implantation of certain biomaterials. This progress report defines mineralization pathway components and identifies the commonalities (and differences) between physiological (e.g., bone remodeling) and pathological calcification formation pathways, based, in part, upon the extent of cellular control within the system. These concepts are discussed in representative examples of calcium phosphate-based pathological mineralization in cancer (breast, thyroid, ovarian, and meningioma) and in cardiovascular disease. In-depth mechanistic understanding of pathological mineralization requires utilizing state-of-the-art materials science imaging and characterization techniques, focusing not only on the final deposits, but also on the earlier stages of crystal nucleation, growth, and aggregation. Such mechanistic understanding will further enable the use of pathological calcifications in diagnosis and prognosis, as well as possibly provide insights into preventative treatments for detrimental mineralization in disease.

Paraplegia as a presentation of primary hyperoxaluria

30% of the patients suffering from hyperoxaluria type 1 are diagnosed only when they already had reached end-stage renal disease. We report the case of a 57-year-old woman with history of chronic kidney failure presenting with paraplegia due to spinal cord compression by thoracic mass-like lesions. Bone biopsy specimen obtained by decompressive laminectomy revealed calcium oxalate deposits. Once diagnosis of primary hyperoxaluria was confirmed, she underwent haemodialysis with incomplete improvement of her neurological disorders and was registered on the waiting list for transplantation.

Recurrent primary hyperoxaluria type 2 leads to early post-transplant renal function loss: A case report

Primary hyperoxaluria type 2 is a rare autosomal recessive disorder caused by glyoxylate reductase/hydroxypyruvate reductase deficiency and characterized by recurrent episodes of nephrolithiasis and nephrocalcinosis. Herein, we describe a case of primary hyperoxaluria type 2 in a 33-year-old man who failed to respond to conventional therapies; thus renal transplantation was performed. This case demonstrated that, although primary hyperoxaluria type 2 is rare, hyperoxaluria should be suspected and blood oxalate and stone component be examined in patients with recurrent episodes of nephrolithiasis, particularly in those who are unresponsive to conventional therapies. Combined liver-kidney transplant may be required as kidney transplant alone is not likely to be successful.

Unusual clinical outcome of primary Hyperoxaluria type 1 in Tunisian patients carrying 33_34InsC mutation

Background

Primary hyperoxaluria type 1 (PH1), is a rare and heterogeneous disease and one of major causes of renal insufficiency in Tunisia, caused by mutations in the AGXT gene. 33-34InsC mutation, was mainly described in children with a severe clinical feature leading to early death, but it was uncommonly reported in adult patients.

Methods

Common mutations in AGXT were tested using PCR/RFLP technique in 111 patients (68 adult, 43 children) with suspected PH1.

Results

We described 16 cases (eight adult and eight children) with a 33-34InsC mutation with a median age of 24 years [6 months - 73 years]. All children were in end stage renal disease (ESRD) at the median age of 3 years due to lithiasis and/or nephrocalcinosis. Unfortunately, 75% of them died with a median age of 2.5 years. For the majority of adults only spontaneous elimination of urolithiasis were noted, 37.5% preserved until now a normal renal function and 62.5% of them reached ESRD at the median age of 55.8 ± 12.31 years old.

Conclusion

In this study 33-34InsC mutation gives a controversial clinical effect in children and adults. The implication of other genetic and/or environmental factors can play a crucial role in determining the ultimate phenotype.

Clinical and Genetic Profile of Indian Children with Primary Hyperoxaluria

Primary hyperoxaluria (PH) has heterogeneous renal manifestations in infants and children. This often leads to delay in diagnosis. In the past 3 years, genetic samples were sent for seven children with a clinical diagnosis of PH. Their medical records were reviewed for clinical presentation and outcomes. Of the seven children, three were males. The median age of presentation was 4.9 years with the youngest presenting at 3 months of age. Nephrolithiasis, the most common presentation was associated with renal dysfunction in two children. Two children with no significant history presented in end-stage renal disease (ESRD). The sibling of one of the children in ESRD, with a history of consanguinity in parents, was screened for asymptomatic nephrolithiasis. Bilateral multiple renal calculi were found in majority of children followed by echogenic kidneys on ultrasound examination. Genetic analysis suggested PH Type 1 in five children and type 2 in two children. The mutations detected in our cohort were different from the previously reported common mutations. There was no obvious genotype-phenotype correlation noticed. Three children in ESRD are on maintenance dialysis. Nephrolithiasis being a common presentation of PH needs prompt evaluation. Mutations are generally population specific, and whole gene sequence analysis is critical in diagnosis.

Phenotype-Genotype Correlations and Estimated Carrier Frequencies of Primary Hyperoxaluria

Primary hyperoxaluria (PH) is a rare autosomal recessive disease characterized by oxalate accumulation in the kidneys and other organs. Three loci have been identified: AGXT (PH1), GRHPR (PH2), and HOGA1 (PH3). Here, we compared genotype to phenotype in 355 patients in the Rare Kidney Stone Consortium PH registry and calculated prevalence using publicly available whole-exome data. PH1 (68.4% of families) was the most severe PH type, whereas PH3 (11.0% of families) showed the slowest decline in renal function but the earliest symptoms. A group of patients with disease progression similar to that of PH3, but for whom no mutation was detected (11.3% of families), suggested further genetic heterogeneity. We confirmed that the AGXT p.G170R mistargeting allele resulted in a milder PH1 phenotype; however, other potential AGXT mistargeting alleles caused more severe (fully penetrant) disease. We identified the first PH3 patient with ESRD; a homozygote for two linked, novel missense mutations. Population analysis suggested that PH is an order of magnitude more common than determined from clinical cohorts (prevalence, approximately 1:58,000; carrier frequency, approximately 1:70). We estimated PH to be approximately three times less prevalent among African Americans than among European Americans because of a limited number of common European origin alleles. PH3 was predicted to be as prevalent as PH1 and twice as common as PH2, indicating that PH3 (and PH2) cases are underdiagnosed and/or incompletely penetrant. These results highlight a role for molecular analyses in PH diagnostics and prognostics and suggest that wider analysis of the idiopathic stone-forming population may be beneficial.

Vitamin B6 in primary hyperoxaluria I: first prospective trial after 40 years of practice

BACKGROUND AND OBJECTIVES

Primary hyperoxaluria type I (PH I) is caused by deficiency of the liver-specific enzyme alanine-glyoxylate:aminotransferase (AGT). Many mutations are known to perturb AGT protein folding. Vitamin B6 (B6) is the only specific drug available for treatment. Although B6 has been used for >40 years, controlled data on B6 efficacy are lacking. Therefore, this study investigated the absolute and relative change of urinary oxalate (Uox) excretion under increasing dosages of B6, the first prospective trial to do so.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

B6 response was studied in 12 patients (7 male patients) with genetically confirmed PH I (3 Gly170Arg homozygous, 5 compound Gly170Arg and/or Phe152Ile heterozygous, and 4 negative for Gly170Arg and/or Phe152Ile mutations) and noncompromised renal function. Efficacy was defined as a 30% relative reduction in Uox excretion. B6 was administered orally starting at 5 mg/kg body weight per day and given in increments of 5 mg/kg every 6 weeks, up to a final dosage of 20 mg/kg per day at week 24. Uox and serum B6 levels were measured every 6 weeks.

RESULTS

Mean relative Uox reduction was 25.5%. Uox declined from 2.09±0.55 (mean±SD) at baseline to 1.52±0.60 mmol/1.73 m(2) per day (P=0.01) at week 24. Serum B6 levels increased from 22.5±8.7 to 1217±776 ng/ml (P<0.001). Six patients showed a ≥30% relative reduction of Uox at week 24.

CONCLUSION

This first prospective trial confirmed B6 efficacy in 50% of patients (three of three homozygous, one of five heterozygous, and two of four patients negative for the Gly170Arg and/or Phe152Ile mutations). Interestingly, no complete biochemical remission was observed, even in the homozygous Gly170Arg study participants. Future trials are necessary to learn more about genotype-related B6 response and B6 metabolism.

Native portal vein embolization for persistent hyperoxaluria following kidney and auxiliary partial liver transplantation

Type 1 primary hyperoxaluria (PH1) causes renal failure, for which isolated kidney transplantation (KT) is usually unsuccessful treatment due to early oxalate stone recurrence. Although hepatectomy and liver transplantation (LT) corrects PH1 enzymatic defect, simultaneous auxiliary partial liver transplantation (APLT) and KT have been suggested as an alternative approach. APLT advantages include preservation of the donor pool and retention of native liver function in the event of liver graft loss. However, APLT relative mass may be inadequate to correct the defect. We here report the first case of native portal vein embolization (PVE) to increase APLT to native liver mass ratio (APLT/NLM-R). Following initial combined APLT-KT, both allografts functioned well, but oxalate plasma levels did not normalize. We postulated the inadequate APLT/NLM-R could be corrected by trans-hepatic native PVE. The resulting increased APLT/NLM-R decreased serum oxalate to normal levels within 1 month following PVE. We conclude that persistently elevated oxalate levels after combined APLT-KT for PH1 treatment, results from inadequate relative functional capacity. This can be reversed by partial native PVE to decrease portal flow to the native liver. This approach might be applicable to other scenarios where partial grafts have been transplanted to replace native liver function.

Massive bone marrow involvement in an end stage renal failure case with erythropoietin-resistant anemia and primary hyperoxaluria

Primary hyperoxaluria is a rare autosomal recessive disorder. Type 1 PH is the most common form and develops due to a defect in a liver specific enzyme the alanine aminotransferase enzyme. As a result of the enzyme deficiency, there is an overproduction of oxalate and excessive urinary excretion. Recurrent urolithiasis and nephrocalcinosis are the most important findings of the disorder and often at the beginning end-stage renal disease develops. This report presents a case backed up by literature of a patient with end stage renal failure and erythropoietin-resistant anaemia whose bone marrow biopsy showed crystal deposition which received delayed diagnosis of oxalosis.

Stroke in primary hyperoxaluria type I

We report the case of a 27-year-old man with a history of previously undiagnosed renal disease that presented with multiple cerebrovascular infarctions. Workup for traditional causes of cerebrovascular infarction including cardiac telemetry, multiple echocardiograms, and hypercoagulative workup was negative. However, a transcranial Doppler detected circulating microemboli at the rate of 14 per hour. A serum oxalate level greater than the supersaturation point of calcium oxalate was detected, providing a potential source of the microemboli. Furthermore, serial imaging recorded rapid mineralization of the infarcted territories. In the absence of any proximal vessel irregularities, atherosclerosis, valvular abnormalities, arrhythmias, or systemic shunt as potential stroke etiology in this patient, we propose that circulating oxalate precipitate may be a potential mechanism for stroke in patients with primary oxalosis.

Oxalosis and livedo reticularis

Oxalosis is a disease caused by the deposition of calcium oxalate in extrarenal tissues, most commonly bone, myocardium, retina, blood vessels, and skin, causing the clinical manifestations of the disease. Involvement of the blood vessels of the skin can give rise to livedo reticularis, acrocyanosis, ulcers, and gangrene. We present the case of a 60-year-old woman with a history of recurrent renal lithiasis that had led to terminal renal failure requiring hemodialysis and, subsequently, peritoneal dialysis. The patient developed tender red-violaceous skin discoloration of sudden onset, consistent with livedo reticularis; the lesions progressed to form ulcers. Skin biopsy revealed oxalate vasculopathy. In this article we describe the characteristics of this rare disorder, its differentiation from calciphylaxis, and the therapeutic options.

Primary hyperoxaluria in a compound heterozygote infant

BACKGROUND

Primary hyperoxaluria type 1 is a rare disorder caused by a defect in the hepatic metabolism of glyoxylate. Cases presenting in infancy are very uncommon and often have a severe course leading to early end-stage renal failure.

METHODS

We treated a case of early presentation of primary hyperoxaluria type 1 and reviewed the relevant literature.

RESULTS

A 4-month-old female infant was admitted to our hospital because of acute renal failure and nephrocalcinosis. Mutational analysis of alanine-glyoxylate aminotransferase gene revealed compound heterozygosity in the infant, confirming the development of primary hyperoxaluria type 1. A few weeks later, the condition of the infant worsened during an interdialytic period and died.

CONCLUSIONS

Interest of this case is based on the coexistence of two mutations of alanine-glyoxylate aminotransferase gene recently reported, and it confirms the severe course of the disease when it presents in infancy. It also highlights the importance of the association of nephrocalcinosis and urolithiasis as key diagnostic manifestations of primary hyperoxaluria type 1.

Pre-emptive liver transplantation for primary hyperoxaluria (PH-I) arrests long-term renal function deterioration

BACKGROUND

Primary hyperoxaluria-I (PH-I) is a serious metabolic disease resulting in end-stage renal disease. Pre-emptive liver transplantation (PLT) for PH-I is an option for children with early diagnosis. There is still little information on its effect on long-term renal function in this situation.

METHODS

Long-term assessment of renal function was conducted using Schwartz's formula (estimated glomerular filtration rate-eGFR) in four children (Group A) undergoing PLT between 2002 and 2008, and a comparison was done with eight gender- and sex-matched controls (Group B) having liver transplantation for other indications.

RESULTS

All patients received a liver graft from a deceased donor. Median follow-up for the two groups was 64 and 94 months, respectively. One child in Group A underwent re-transplantation due to hepatic artery thrombosis, while acute rejection was seen in one. A significant difference was seen in eGFR at transplant (81 vs 148 mL/min/1.73 m(2)) with greater functional impairment seen in the study population. In Group A, renal function reduced by 21 and 11% compared with 37 and 35% in Group B at 12 and 24 months, respectively. At 2 years post-transplantation, there was no significant difference in eGFR between the two groups (72 vs 100 mL/min/1.73 m(2), respectively; P = 0.06).

CONCLUSIONS

Renal function remains relatively stable following pre-emptive LTx for PH-I. With early diagnosis of PH-I, isolated liver transplantation may prevent progression to end-stage renal disease and the need for renal transplantation.

History, epidemiology and regional diversities of urolithiasis

Archeological findings give profound evidence that humans have suffered from kidney and bladder stones for centuries. Bladder stones were more prevalent during older ages, but kidney stones became more prevalent during the past 100 years, at least in the more developed countries. Also, treatment options and conservative measures, as well as 'surgical' interventions have also been known for a long time. Our current preventive measures are definitively comparable to those of our predecessors. Stone removal, first lithotomy for bladder stones, followed by transurethral methods, was definitively painful and had severe side effects. Then, as now, the incidence of urolithiasis in a given population was dependent on the geographic area, racial distribution, socio-economic status and dietary habits. Changes in the latter factors during the past decades have affected the incidence and also the site and chemical composition of calculi, with calcium oxalate stones being now the most prevalent. Major differences in frequency of other constituents, particularly uric acid and struvite, reflect eating habits and infection risk factors specific to certain populations. Extensive epidemiological observations have emphasized the importance of nutritional factors in the pathogenesis of urolithiasis, and specific dietary advice is, nowadays, often the most appropriate for prevention and treatment of urolithiasis.

Two-step transplantation for primary hyperoxaluria: cadaveric liver followed by living donor related kidney transplantation

In PH, PLTX, although ideal in theory, is rarely achieved. Patients usually have reached end-stage kidney disease while requiring combined liver and kidney transplantation. In this combined procedure, the sudden high oxalates mobilization from blood and tissue stores jeopardizes the success of the kidney graft, with a high risk of post-transplant early kidney necrosis or chronic graft damage. Here, we report the case of a three-yr-old girl with PH and ESRF in whom we performed sequentially deceased donor liver transplantation followed four months later by living donor kidney transplant, after normalization of blood oxalate levels and improvement of urinary oxalate output. After this two-step transplantation, our patient showed normalization of renal function with good urinary output and maintained normal blood oxalate levels. This strategy seems to be a reasonable approach in order to avoid acute renal tubular injury because of oxalate excretion in these patients.

Recombinant production of eight human cytosolic aminotransferases and assessment of their potential involvement in glyoxylate metabolism

PH1 (primary hyperoxaluria type 1) is a severe inborn disorder of glyoxylate metabolism caused by a functional deficiency of the peroxisomal enzyme AGXT (alanine-glyoxylate aminotransferase), which converts glyoxylate into glycine using L-alanine as the amino-group donor. Even though pre-genomic studies indicate that other human transaminases can convert glyoxylate into glycine, in PH1 patients these enzymes are apparently unable to compensate for the lack of AGXT, perhaps due to their limited levels of expression, their localization in an inappropriate cell compartment or the scarcity of the required amino-group donor. In the present paper, we describe the cloning of eight human cytosolic aminotransferases, their recombinant expression as His6-tagged proteins and a comparative study on their ability to transaminate glyoxylate, using any standard amino acid as an amino-group donor. To selectively quantify the glycine formed, we have developed and validated an assay based on bacterial GO (glycine oxidase); this assay allows the detection of enzymes that produce glycine by transamination in the presence of mixtures of potential amino-group donors and without separation of the product from the substrates. We show that among the eight enzymes tested, only GPT (alanine transaminase) and PSAT1 (phosphoserine aminotransferase 1) can transaminate glyoxylate with good efficiency, using L-glutamate (and, for GPT, also L-alanine) as the best amino-group donor. These findings confirm that glyoxylate transamination can occur in the cytosol, in direct competition with the conversion of glyoxylate into oxalate. The potential implications for the treatment of primary hyperoxaluria are discussed.

Primary hyperoxaluria causing ESRD and gangrene of extremities leading to amputation

Primary hyperoxaluria is an uncommon, inherited metabolic disorder due to hepatic enzyme deficiencies with consequent hepatic oxalate overproduction and attendant systemic complications. The diagnosis is established on a combination of clinical parameters, elevated urinary excretion of oxalate and glycolate and determination of alanine glyoxylate aminotransferase in the liver tissue. We describe a 45-year-old female with end-stage renal disease secondary to nephrolithiasis, who presented with a fulminating vascular syndrome before confirming the diagnosis of primary hyperoxaluria. This case illustrates that in this infrequent clinical entity, the diagnosis is often delayed with incorrect initial management.

Autopsy findings of a case with oxalosis

Oxalosis, deposition of calcium oxalate in tissues, is the final stage of hyperoxaluric syndromes. Being a rare entity, it is often missed, or the diagnosis is delayed, since the definitive diagnosis requires special laboratory tests. Kidneys, the walls of blood vessels, and bones are the major sites for crystal deposition. We report the autopsy findings of a 4-year-old girl who presented with end-stage renal disease in which the clinical presentation was consistent with primary hyperoxaluria Type I. The case is unusual, as there was extensive crystal deposition throughout the body, including in tissues that are rarely involved, such as ovaries, fallopian tubes, uterus, thymus, salivary glands, pancreas, and bladder.

Skeletal features of primary hyperoxaluria type 1, revisited

PURPOSE

The purpose of this study was to describe the skeletal manifestations of primary hyperoxaluria type 1 (PH1), the most common of the primary hyperoxalurias.

METHODS

We clinically and radiographically reviewed 12 consecutive patients diagnosed with PH1, aged between 2 and 17 years. All patients had evidence of some type of renal involvement, 4 of whom were at end-stage renal disease (ESRD) and were under dialysis.

RESULTS

The main symptom was skeletal pain and was present only in the 4 severely involved patients and appeared during the second year of dialysis. The 2 most severely involved patients had evidence of pathological fractures. Radiological signs were present in patients with or without symptoms. These radiological signs were of two distinct types: those almost specific of oxalosis, such as dense and radiolucent metaphyseal bands and vertebral osteocondensations, which are found mainly in the severely involved individuals, and those less specific, such as signs of renal osteodystrophy, which are also found in less severely involved patients. Interestingly, our study revealed the presence of spondylolysis in 25% of cases. This latter finding is unique and has not previously been reported in the literature.

CONCLUSIONS

The skeletal manifestations of PH1 include specific and less specific radiological signs, with some patients being asymptomatic, and others presenting with bone pain and pathological fractures, as well as spondylolysis.

[Inherited monogenic kidney stone diseases: recent diagnostic and therapeutic advances]

Hereditary monogenic kidney stone diseases are rare diseases, since they account for nearly 2% of nephrolithiasis cases in adults and 10% in children. Most of them are severe, because they frequently are associated with nephrocalcinosis and lead to progressive impairment of renal function unless an early and appropriate etiologic treatment is instituted. Unfortunately, treatment is often lacking or started too late since they are often misdiagnosed or overlooked. The present review reports the genotypic and phenotypic characteristics of monogenic nephrolithiases, with special emphasis on the recent advances in the field of diagnosis and therapeutics. Monogenic stone diseases will be classified into three groups according to their mechanism: (1) inborn errors of the metabolism of oxalate (primary hyperoxalurias), uric acid (hereditary hyperuricemias) or other purines (2,8-dihydroxyadeninuria), which, in addition to stone formation, result in crystal deposition in the renal parenchyma; (2) congenital tubulopathies affecting the convoluted proximal tubule (such as Dent's disease, Lowe syndrome or hypophosphatemic rickets), the thick ascending limb of Henlé's loop (such as familial hypomagnesemia and Bartter's syndromes) or the distal past of the nephron (congenital distal tubular acidosis with or without hearing loss), which are frequently associated with nephrocalcinosis, phosphatic stones and extensive tubulointerstitial fibrosis; (3) cystinuria, an isolated defect in tubular reabsorption of cystine and dibasic aminoacids, which results only in the formation of stones but requires a cumbersome treatment. Analysis of stones appears of crucial value for the early diagnosis of these diseases, as in several of them the morphology and composition of stones is specific. In other cases, especially if nephrocalcinosis, phosphatic stones or proteinuria are present, the evaluation of blood and urine chemistry, especially with regard to calcium, phosphate and magnesium, is the key of diagnosis. Search for mutations is now increasingly performed in as much as genetic counselling is important for the detection of heterozygotes in autosomic recessive diseases and of carrier women in X-linked diseases. In conclusion, better awareness to the rare monogenic forms of nephrolithiasis and/or nephrocalcinosis should allow early diagnosis and treatment which are needed to prevent or substantially delay progression of end-stage renal disease. Analysis of every first stone both in children and in adults should never be neglected, in order to early detect unusual forms of nephrolithiasis requiring laboratory evaluation and deep etiologic treatment.

A case of late-onset primary hyperoxaluria

Primary hyperoxaluria is a rare autosomal recessive disorder resulting in diffuse deposition of insoluble oxalate crystals in multiple organs. Two-thirds of patients have nephrolithiasis by 5 years of age and 80% die of renal failure by 20 years of age. Rarely, the disease will present in adulthood, with the onset of symptoms occurring as late as the sixth decade. Oxalosis is a condition in which the highly insoluble calcium oxalate crystals are deposited in extrarenal tissue. Pathologic involvement of bone is recognized as osteosclerosis on radiograph. Oxalosis should be considered in patients with osteosclerotic bone changes and chronic renal failure and should not be misinterpreted as renal osteodystrophy. We describe here a case of oxalosis in a 33-year-old man.

Insuffisance rénale terminale d'origine lithiasique : fréquence, causes et prévention

Nephrolithiasis still remains a too frequent - and under-appreciated - cause of end-stage renal disease (ESRD), and this is all the most unfortunate since such an untoward course is now preventable in most cases. Among 1391 patients who started maintenance dialysis at Necker hospital between 1989 and 2000, nephrolithiasis was identified as the cause of ESRD in 45 of them, an overall prevalence of 3.2%. Infection stones accounted for 42.2% of cases, calcium stones for 26.7%, uric acid stones for 17.8% and hereditary diseases for 13.3%. The proportion of nephrolithiasis-associated ESRD declined from 4.7% to 2.2% from the 1989-1991 to the 1998-2000 period, as a result of the decreased incidence of ESRD in patients with infection and calcium nephrolithiasis. Based on our observations and on published reports, it emerges that most cases of nephrolithiasis-associated ESRD were due to sub-optimal management (especially in the case of infection or cystine stones) or to late (or erroneous) etiologic diagnosis, precluding early institution of appropriate therapeutic measures. In particular, several patients with primary hyperoxaluria or 2,8-dihydroxyadeninuria were diagnosed while already on dialysis or after unsuccessful kidney transplantation, due to wrong initial diagnosis. In conclusion, thanks to recent advances in diagnosis and management of stone formers, ESRD should now be prevented in the great majority of patients, at the condition of early etiologic diagnosis based on accurate morphoconstitutional analysis of calculi and metabolic evaluation, and early implementation of appropriate preventive medical treatment.

Cadaveric orthotopic auxiliary split liver transplantation and kidney transplantation: an alternative for type 1 primary hyperoxaluria

Liver transplantation (LTX) corrects the enzymatic defect responsible for type 1 primary hyperoxaluria (PH1). It has been advocated in combination with kidney transplantation (KTX) in patients with renal failure from PH1 because KTX alone can result in early graft loss. A 58-year-old male patient with PH1 on hemodialysis underwent resection of the left lateral segment of the liver followed by orthotopic auxiliary left lateral segment liver transplantation and kidney transplantation from a deceased donor. The serum oxalate dropped from 34.8 micromol/L before transplant to 3.6-8.3 in the first months posttransplant to <1 micromol/L (normal range 0.4-3.0). One year after posttransplant, the patient has an iothalamate glomerular filtration rate of 58 ml/min. Orthotopic auxiliary LTX is an alternative to whole LTX in PH1. By using a split deceased donor liver, it does not deprive the donor pool and protects the recipient from liver failure in case of graft loss.

Livedo reticularis: An update

Livedo reticularis (LR) is a well-known, relatively common physical finding consisting of macular, violaceous, connecting rings that form a netlike pattern (Fig 1). In most cases, it is a completely benign finding related to cold exposure. However, there are many potential causes (Table I), and this can make the evaluation of a patient presenting with this finding very difficult. An excellent review of the topic by Fleischer and Resnick was published in 1990. We have endeavored to update the literature and provide clinicians with guidance regarding the evaluation and treatment of patients presenting with LR.

The primary hyperoxalurias: an algorithm for diagnosis

BACKGROUND/AIMS

The primary hyperoxalurias (PHs) are inborn errors of metabolism resulting in increased urinary excretion of oxalate. Nephrolithiasis, nephrocalcinosis, and renal failure result. Renal failure can occur as early as infancy or as late as the sixth decade of life, and if not addressed promptly, results in severe morbidity and mortality related to systemic oxalate deposition (oxalosis). Clinicians are likely to encounter few PH patients during a practicing lifetime. Definitive diagnosis requires special studies performed in only a small number of laboratories worldwide. Accordingly, delays in diagnosis are common.

METHODS

An evidence-based guideline for diagnosis was developed.

RESULTS

Patients with stones or nephrocalcinosis in childhood, recurrent calcium oxalate stones in adulthood, or renal insufficiency associated with stones or nephrocalcinosis should be evaluated for PH. A systematic approach to measurement of urine oxalate, glycolate and glycerate, and plasma oxalate is provided. Age-related variation in urine oxalate requires attention to normal ranges. Molecular analysis for mutations of the AGXT gene (PH, type I) or GRHPR gene (PH, type II) is definitive in some patients, while liver enzyme analysis is required for confirmation of the diagnosis in the remainder.

CONCLUSION

An evidence-based algorithm will facilitate recognition and diagnosis of patients with the PHs, permitting earlier treatment.