Primary hyperoxaluria type 1: practical and ethical issues

Case Report: effect of lumasiran treatment in a late preterm baby with antenatal diagnosis of primary hyperoxaluria type 1

Background

Primary hyperoxaluria type 1 (PH1) is a rare disease with autosomal recessive transmission, characterized by increased urinary excretion of oxalate, resulting in chronic kidney disease secondary to recurrent urolithiasis, nephrocalcinosis, and accumulation of oxalate in various organs and tissues (systemic oxalosis). Since 2020, an innovative pharmacological approach, namely, lumasiran, has been added to the therapeutic armamentarium (dialysis and liver-kidney transplantation). The purpose of this paper is to describe the effect of lumasiran initiated at 10 days of life in a newborn with prenatally diagnosed PH1. A female fetus was prenatally diagnosed with hyperoxaluria type 1, based on family history and genetic testing. Her brother had the onset of the disease at 2 months of age and underwent liver and kidney transplantation at 13 months and 8 years of age, respectively. The baby was born late preterm at 36 weeks + 4 days of gestation via spontaneous labor, and lumasiran for compassionate use was started on the tenth day of life. At 20 months of age, the baby showed normal urinary oxalate values and kidney function, while the plasma oxalate level was under the threshold of oversaturation. There were no signs of systemic oxalosis.

Conclusions

Early use of lumasiran in young infants, who do not yet show signs of the disease, represents a therapeutic challenge for the pediatric nephrologist. The ability of the drug to act on the hepatocyte of the newborn and the most appropriate dosage to be used in these very young babies have yet to be clarified.

Qualitative assessment of the patient experience of primary hyperoxaluria type 1: an observational study

BACKGROUND

Without effective intervention, primary hyperoxaluria type 1 (PH1) causes oxalate-induced kidney damage, leading to end-stage kidney disease and serious complications throughout the body. Although PH1 carries a heavy burden that impacts quality of life, literature on the experiences of those living with PH1 and caring for patients with PH1 is limited. This study aimed to describe the diagnostic journey in PH1 and characterize patients' and caregivers' self-reported experiences throughout the disease course.

METHODS

This was an observational study involving in-depth, semi-structured telephone interviews. Dominant trends were assessed using constant comparative analysis to identify themes in interviewees' descriptions of their experiences. Individuals aged ≥ 12 years and caregivers of children aged 6-17 years with genetically confirmed PH1 were eligible. Informed consent/assent and ability to read and speak English were required.

RESULTS

Interviewees (16 patients, 12 caregivers) reported a prolonged diagnostic journey due to low disease awareness, among other factors. Upon diagnosis, PH1 was frequently symptomatic, typically involving kidney stone-related symptoms but also potentially symptoms arising beyond the kidneys. PH1 most commonly led to worry and social impairment in adolescents, impaired physical function in adults, and a range of impacts on caregivers. In late-stage disease, dialysis was the most burdensome aspect of living with PH1 (due to time requirements, limitations from living with a catheter, etc.), and this burden was exacerbated by the COVID-19 pandemic. Benefits desired from PH1 management included reductions in laboratory measures of oxalate burden, kidney stone and urination frequency, and oxalate-related skin ulcers.

CONCLUSIONS

PH1 greatly impacts patients' and caregivers' lives, primarily due to burdensome disease manifestations and associated emotional, physical, and practical impacts, as well as disease management challenges - particularly those related to dialysis in late-stage disease.

Stiripentol and Lumasiran as a Rescue Therapy for Oxalate Nephropathy Recurrence After Kidney Transplantation in an Adult Patient With Primary Hyperoxaluria Type 1

Primary hyperoxaluria type 1 is a rare cause of kidney failure. Stiripentol, an inhibitor of lactate dehydrogenase A, and lumasiran, a small interfering RNA targeting glycolate oxidase, have been proposed as therapeutic options, but clinical data are scarce, especially in adults and transplanted patients. We describe the case of a 51-year-old patient with a biopsy-proven recurrence of oxalate nephropathy after a kidney-only transplantation. He received stiripentol and lumasiran without adverse events. Fourteen months after transplantation, graft function, serum, and urinary oxalate levels have remained stable, and kidney biopsy showed a complete regression of oxalate crystals. Further studies are needed to assess whether this strategy is effective and could replace liver-kidney transplantation.

Effect of liver transplantation with primary hyperoxaluria type 1: Five case reports and review of literature

BACKGROUND

Primary hyperoxaluria type 1 (PH1) is a rare autosomal recessive disease stemming from a deficiency in liver-specific alanine-glyoxylate aminotransferase, resulting in increased endogenous oxalate deposition and end-stage renal disease. Organ transplantation is the only effective treatment. However, its approach and timing remain controversial.

CASE SUMMARY

We retrospectively analyzed 5 patients diagnosed with PH1 from the Liver Transplant Center of the Beijing Friendship Hospital from March 2017 to December 2020. Our cohort included 4 males and 1 female. The median age at onset was 4.0 years (range: 1.0-5.0), age at diagnosis was 12.2 years (range: 6.7-23.5), age at liver transplantation (LT) was 12.2 years (range: 7.0-25.1), and the follow-up time was 26.3 mo (range: 12.8-40.1). All patients had delayed diagnosis, and 3 patients had progressed to end-stage renal disease by the time they were diagnosed. Two patients received preemptive LT; their estimated glomerular filtration rate was maintained at > 120 mL/min/1.73 m², indicating a better prognosis. Three patients received sequential liver and kidney transplantation. After transplantation, serum and urinary oxalate decreased, and liver function recovered. At the last follow-up, the estimated glomerular filtration rates of the latter 3 patients were 179, 52 and 21 mL/min/1.73 m².

CONCLUSION

Different transplantation strategies should be adopted for patients based on their renal function stage. Preemptive-LT offers a good therapeutic approach for PH1.

Clinical and molecular characterization of a large primary hyperoxaluria cohort from Saudi Arabia: a retrospective study

BACKGROUND

Primary hyperoxalurias (PHs) constitute rare disorders resulting in abnormal glyoxalate metabolism. PH-associated phenotypes range from progressive nephrocalcinosis and/or recurrent urolithiasis to early kidney failure.

METHODS

A retrospective study was conducted for patients with confirmed PH diagnoses from three tertiary centers in Saudi Arabia. Detailed clinical molecular diagnosis was performed for 25 affected individuals. Whole exome sequencing (WES)-based molecular diagnosis was performed for all affected individuals.

RESULTS

The male:female ratio was 52% male (n = 13) and 48% female (n = 12), and consanguinity was present in 88%. Nephrolithiasis and/or nephrocalcinosis were present in all patients. Kidney stones were present in 72%, nephrocalcinosis in 60%, hematuria in 32%, proteinuria in 16%, abdominal pain in 36%, developmental delay in 8%, and chronic kidney disease stage 5 (CKD stage 5) was observed in 28% of the patients. The most common PH disorder was type I caused by variants in the AGXT gene, accounting for 56%. The GRHPR gene variants were identified in 4 patients, 16% of the total cases. Seven patients did not reveal any associated variants. Missense variants were the most commonly observed variants (48%), followed by frame-shift duplication variants (28%).

CONCLUSIONS

Characterization of the genetic and clinical aspects of PH in this unique population provides direction for improved patient management and further research. A higher resolution version of the Graphical abstract is available as Supplementary information.

Primary hyperoxaluria type 1 in developing countries: novel challenges in a new therapeutic era

Primary hyperoxaluria type 1 (PH1) is an autosomal recessive inborn error of metabolism characterized by marked hepatic overproduction of oxalate due to deficiency of hepatic peroxisomal alanine-glyoxylate aminotransferase caused by AGXT gene mutation. One major hallmark of PH1 in developed as well as developing countries (DC) is the diagnostic delay. Notably in DC, where the disease is most prevalent and probably underdiagnosed, there are many challenges in PH1 diagnosis and management, with economic constrains and ethical concerns. This has led to the existing gap in the management of PH1 between developed and DC, which is expected to further deepen with the advent of novel therapeutic agents unless appropriate actions are taken. Until recently, treatment possibilities were limited to supportive measures. Thanks to a better understanding of the molecular basis of the disease a number of new therapies are developed, or being developed, leading to profound changes in management strategies. In this review we discuss the current situation of PH1 in DC as well as the accessibility challenges and the advantages of using promising novel therapeutics to bridge the currently existing gap. We also provide an overview of an integrated approach to ensure equitable access of sustainable therapeutics to PH1 patients in DC. This is expected to reduce global PH1 healthcare disparities, improve its standard of care and reduce disability linked to extrarenal complications of PH1 by implementing personalized medicine.

Primary hyperoxaluria: the pediatric nephrologist's point of view

The clinical presentation of primary hyperoxaluria in children ranges from mildly symptomatic nephrocalcinosis to very early onset end-stage kidney failure with systemic oxalosis, a devastating complication. We review the various manifestations of pediatric hyperoxaluria, treatment options for children with preserved kidney function and appropriate dialysis regimens. Liver or combined liver/kidney transplantation is currently the only definitive treatment for primary hyperoxaluria type 1, but novel RNA interference treatments offer hope for the future. Finally, we address the medical and ethical dilemmas facing pediatricians treating children with hyperoxaluria.

Clinical and economic impact of primary hyperoxaluria: a retrospective claims analysis

BACKGROUND: Primary hyperoxaluria (PH) is a family of rare, life-threatening genetic liver disorders characterized by elevated production and excretion of oxalate. To date, the clinical and economic burden associated with PH has not been well characterized due to the rarity of the disease and previous challenges with diagnostic coding that prevented proper identification of patients with PH in claims data. OBJECTIVE: To characterize the clinical and economic costs, as well as health care resource utilization (HCRU), associated with PH relative to a matched cohort of patients without PH. METHODS: Data from the IQVIA PharMetrics Plus Database were used to conduct a retrospective matched-cohort study to compare differences in clinical characteristics, HCRU, and pharmacy and medical costs in patients with PH compared with a matched cohort of patients without PH from January 2014 to December 2019. RESULTS: Overall, 324 patients were included in the PH cohort and 1,620 patients were in the non-PH cohort. The mean age of PH patients was 48.1 years, and approximately 58% of the sample were male. Significantly more patients in the PH cohort than the non-PH cohort were diagnosed with stage 2 chronic kidney disease (CKD; 3.1% vs 0.4%, respectively; P < 0.001), stage 3 CKD (4.6% vs 0.5%; P < 0.001), stage 4 CKD (2.5% vs 0.1%; P < 0.001), and stage 5 CKD or end-stage renal disease (ESRD; 2.2% vs 0.1%; P < 0.001). PH patients had a significantly higher mean Charlson Comorbidity Index composite score than patients in the non-PH cohort (0.79 vs 0.37; P < 0.001). HCRU was significantly higher in patients with PH. The PH cohort had a significantly higher proportion of patients with at least 1 visit to clinicians specializing in nephrology (19% vs 0.4%, respectively; P < 0.001), cardiology (22% vs 12%; P < 0.001), ophthalmology (16% vs 7%; P < 0.001), general surgery (9% vs 6%; P = 0.011), and urology (65% vs 6%; P < 0.001) compared with patients without PH. Mean total annual health care costs in the PH cohort were 65% higher than in the non-PH cohort ($22,549 vs $7,852, respectively; P < 0.001). Similar results were found for total prescription drug costs ($4,125 vs $2,464; P = 0.012). CONCLUSIONS: Despite the rarity of PH, patients with this disease incur substantial clinical and economic burden and may cause financial strain on the health care system. Additional research is warranted to understand the economic and clinical burden of PH stratified by the 3 subtypes of the disease. DISCLOSURES: Funding for this research was provided by Dicerna Pharmaceuticals. Mucha and Hoppe are employed by Dicerna Pharmaceuticals. Silber Miyasoto, Skaar, and Wang are employed by Trinity Life Sciences, which was contracted by Dicerna Pharmaceuticals to conduct the study analysis. Langman is consultant to Dicerna Pharmaceuticals. This study was presented as a poster at the AMCP Nexus 2020 (virtual), October 19-23, 2020, and American Society of Nephrology 2020 (virtual), October 19-25, 2020.

Lumasiran, an RNAi Therapeutic for Primary Hyperoxaluria Type 1

BACKGROUND

Primary hyperoxaluria type 1 (PH1) is a rare genetic disease caused by hepatic overproduction of oxalate that leads to kidney stones, nephrocalcinosis, kidney failure, and systemic oxalosis. Lumasiran, an investigational RNA interference (RNAi) therapeutic agent, reduces hepatic oxalate production by targeting glycolate oxidase.

METHODS

In this double-blind, phase 3 trial, we randomly assigned (in a 2:1 ratio) patients with PH1 who were 6 years of age or older to receive subcutaneous lumasiran or placebo for 6 months (with doses given at baseline and at months 1, 2, 3, and 6). The primary end point was the percent change in 24-hour urinary oxalate excretion from baseline to month 6 (mean percent change across months 3 through 6). Secondary end points included the percent change in the plasma oxalate level from baseline to month 6 (mean percent change across months 3 through 6) and the percentage of patients with 24-hour urinary oxalate excretion no higher than 1.5 times the upper limit of the normal range at month 6.

RESULTS

A total of 39 patients underwent randomization; 26 were assigned to the lumasiran group and 13 to the placebo group. The least-squares mean difference in the change in 24-hour urinary oxalate excretion (lumasiran minus placebo) was -53.5 percentage points (P<0.001), with a reduction in the lumasiran group of 65.4% and an effect seen as early as month 1. The between-group differences for all hierarchically tested secondary end points were significant. The difference in the percent change in the plasma oxalate level (lumasiran minus placebo) was -39.5 percentage points (P<0.001). In the lumasiran group, 84% of patients had 24-hour urinary oxalate excretion no higher than 1.5 times the upper limit of the normal range at month 6, as compared with 0% in the placebo group (P<0.001). Mild, transient injection-site reactions were reported in 38% of lumasiran-treated patients.

CONCLUSIONS

Lumasiran reduced urinary oxalate excretion, the cause of progressive kidney failure in PH1. The majority of patients who received lumasiran had normal or near-normal levels after 6 months of treatment. (Funded by Alnylam Pharmaceuticals; ILLUMINATE-A ClinicalTrials.gov number, NCT03681184.).

Deleterious AGXT Missense Variant Associated with Type 1 Primary Hyperoxaluria (PH1) in Zwartbles Sheep

Severe oxalate nephropathy has been previously reported in sheep and is mostly associated with excessive oxalate in the diet. However, a rare native Dutch breed (Zwartbles) seems to be predisposed to an inherited juvenile form of primary hyperoxaluria and no causative genetic variant has been described so far. This study aims to characterize the phenotype and genetic etiology of the inherited metabolic disease observed in several purebred Zwartbles sheep. Affected animals present with a wide range of clinical signs including condition loss, inappetence, malaise, and, occasionally, respiratory signs, as well as an apparent sudden unexpected death. Histopathology revealed widespread oxalate crystal deposition in kidneys of the cases. Whole-genome sequencing of two affected sheep identified a missense variant in the ovine AGXT gene (c.584G>A; p.Cys195Tyr). Variants in AGXT are known to cause type I primary hyperoxaluria in dogs and humans. Herein, we present evidence that the observed clinicopathological phenotype can be described as a form of ovine type I primary hyperoxaluria. This disorder is explained by a breed-specific recessively inherited pathogenic AGXT variant. Genetic testing enables selection against this fatal disorder in Zwartbles sheep as well as more precise diagnosis in animals with similar clinical phenotype. Our results have been incorporated in the Online Mendelian Inheritance in Animals (OMIA) database (OMIA 001672-9940).

Combined liver-kidney transplantation for primary hyperoxaluria type I in children: Single Center Experience

Primary hyperoxalurias are rare inborn errors of metabolism with deficiency of hepatic enzymes that lead to excessive urinary oxalate excretion and overproduction of oxalate which is deposited in various organs. Hyperoxaluria results in serious morbid-ity, end stage kidney disease (ESKD), and mortality if left untreated. Combined liver kidney transplantation (CLKT) is recognized as a management of ESKD for children with hyperoxaluria type 1 (PH1). This study aimed to report outcome of CLKT in a pediatric cohort of PH1 patients, through retrospective analysis of data of 8 children (2 girls and 6 boys) who presented by PH1 to Wadi El Nil Pediatric Living Related Liver Transplant Unit during 2001-2017. Mean age at transplant was 8.2 ± 4 years. Only three of the children underwent confirmatory genotyping. Three patients died prior to surgery on waiting list. The first attempt at CLKT was consecutive, and despite initial successful liver transplant, the girl died of biliary peritonitis prior to scheduled renal transplant. Of the four who underwent simultaneous CLKT, only two survived and are well, one with insignificant complications, and other suffered from abdominal Burkitt lymphoma managed by excision and resection anastomosis, four cycles of rituximab, cyclophosphamide, vincristine, and prednisone. The other two died, one due to uncontrollable bleeding within 36 hours of procedure, while the other died awaiting renal transplant after loss of renal graft to recurrent renal oxalosis 6 months post-transplant. PH1 with ESKD is a rare disease; simultaneous CLKT offers good quality of life for afflicted children. Graft shortage and renal graft loss to oxalosis challenge the outcome.

Skin microvascular dysfunction as an early cardiovascular marker in primary hyperoxaluria type I

BACKGROUND

Primary hyperoxaluria type 1 (PH1) is an orphan inborn error of oxalate metabolism leading to hyperoxaluria, progressive renal failure, oxalate deposition, and increased cardiovascular complications. As endothelial dysfunction and arterial stiffness are early markers of cardiovascular risk, we investigated early endothelial and vascular dysfunction in young PH1 patients either under conservative treatment (PH1-Cons) or after combined kidney liver transplantation (PH1-T) in comparison to healthy controls (Cont-H) and patients with a past of renal transplantation (Cont-T).

METHODS

Skin microvascular function was non-invasively assessed by laser Doppler flowmetry before and after stimulation by current, thermal, or pharmacological (nitroprussiate (SNP) or acetylcholine (Ach)) stimuli in young PH1 patients and controls.

RESULTS

Seven PH1-Cons (6 F, median age 18.2) and 6 PH1-T (2 F, median age 13.3) were compared to 96 Cont-H (51 F, median age 14.2) and 6 Cont-T (4 F, median age 14.5). The endothelium-independent vasodilatation (SNP) was severely decreased in PH1-T compared to Cont-H. Ach, current-induced vasodilatation (CIV), and thermal response was increased in PH1-Cons and Cont-T compared to controls.

CONCLUSIONS

PH1-T patients displayed severely decreased smooth muscle capacity to vasodilate. An exacerbated endothelial-dependent vasodilation suggests a role for silent inflammation in the early dysfunction of microcirculation observed in PH1-Cons and Cont-T.

Molecular basis of primary hyperoxaluria: clues to innovative treatments

Primary hyperoxalurias (PHs) are rare inherited disorders of liver glyoxylate metabolism, characterized by the abnormal production of endogenous oxalate, a metabolic end-product that is eliminated by urine. The main symptoms are related to the precipitation of calcium oxalate crystals in the urinary tract with progressive renal damage and, in the most severe form named Primary Hyperoxaluria Type I (PH1), to systemic oxalosis. The therapies currently available for PH are either poorly effective, because they address the symptoms and not the causes of the disease, or highly invasive. In the last years, advances in our understanding of the molecular bases of PH have paved the way for the development of new therapeutic strategies. They include (i) substrate-reduction therapies based on small-molecule inhibitors or the RNA interference technology, (ii) gene therapy, (iii) enzyme administration approaches, (iv) colonization with oxalate-degrading intestinal microorganisms, and, in PH1, (v) design of pharmacological chaperones. This paper reviews the basic principles of these new therapeutic strategies and what is currently known about their application to PH.

Successful long-term outcome of pediatric liver-kidney transplantation: a single-center study

INTRODUCTION

Liver-kidney transplantation is a rare procedure in children, with just ten to 30 cases performed annually worldwide. The main indications are autosomal recessive polycystic liver-kidney disease and primary hyperoxaluria. This study aimed to report outcomes of liver-kidney transplantation in a cohort of pediatric patients.

METHODS

We retrospectively analyzed all pediatric liver-kidney transplantations performed in our center between September 2000 and August 2015. Patient data were obtained by reviewing inpatient and outpatient medical records and our transplant database.

RESULTS

A total of 14 liver-kidney transplants were performed during the study period, with a median patient age and weight at transplant of 144.4 months (131.0-147.7) and 27.3 kg (12.0-45.1), respectively. The indications for liver-kidney transplants were autosomal recessive polycystic liver-kidney disease (8/14), primary hyperoxaluria -1 (5/14), and idiopathic portal hypertension with end-stage renal disease (1/14). Median time on waiting list was 8.5 months (5.7-17.3). All but two liver-kidney transplants were performed simultaneously. Patients with primary hyperoxaluria-1 tended to present a delayed recovery of renal function compared with patients transplanted for other indications (62.5 vs 6.5 days, respectively, P 0.076). Patients with liver-kidney transplants tended to present a lower risk of acute kidney rejection than patients transplanted with an isolated kidney transplant (7.2% vs 32.7%, respectively; P < 0.07). Patient and graft survival at 1, 3, and 5 years were 100%, 91.7%, 91.7%, and 91.7%, 83.3%, 83.3%, respectively. No other grafts were lost.

CONCLUSION

Long-term results of liver-kidney transplants in children are encouraging, being comparable with those obtained in isolated liver transplantation.

Folding Defects Leading to Primary Hyperoxaluria

Protein misfolding is becoming one of the main mechanisms underlying inherited enzymatic deficits. This review is focused on primary hyperoxalurias, a group of disorders of glyoxylate detoxification associated with massive calcium oxalate deposition mainly in the kidneys. The most common and severe form, primary hyperoxaluria Type I, is due to the deficit of liver peroxisomal alanine/glyoxylate aminotransferase (AGT). Various studies performed in the last decade clearly evidence that many pathogenic missense mutations prevent the AGT correct folding, leading to various downstream effects including aggregation, increased degradation or mistargeting to mitochondria. Primary hyperoxaluria Type II and primary hyperoxaluria Type III are due to the deficit of glyoxylate reductase/hydroxypyruvate reductase (GRHPR) and 4-hydroxy-2-oxoglutarate aldolase (HOGA1), respectively. Although the molecular features of pathogenic variants of GRHPR and HOGA1 have not been investigated in detail, the data available suggest that some of them display folding defects. Thus, primary hyperoxalurias can be ranked among protein misfolding disorders, because in most cases the enzymatic deficit is due to the inability of each enzyme to reach its native and functional conformation. It follows that molecules able to improve the folding yield of the enzymes involved in each disease form could represent new therapeutic strategies.

Clinical spectrum of primary hyperoxaluria type 1: Experience of a tertiary center

BACKGROUND AND AIM

Primary hyperoxalurias are rare inborn errors of metabolism resulting in increased endogenous production of oxalate that leads to excessive urinary oxalate excretion. Diagnosis of primary hyperoxaluria type 1 (PH1) is a challenging issue and depends on diverse diagnostic tools including biochemical analysis of urine, stone analysis, renal biopsy, genetic studies and in some cases liver biopsy for enzyme assay. We characterized the clinical presentation as well as renal and extrarenal phenotypes in PH1 patients.

METHODS

This descriptive cohort study included patients with presumable PH1 presenting with nephrolithiasis and/or nephrocalcinosis (NC). Precise clinical characterization of renal phenotype as well as systemic involvement is reported. AGXT mutational analysis was performed to confirm the diagnosis of PH1.

RESULTS

The study cohort included 26 patients with presumable PH1 with male to female ratio of 1.4:1. The median age at time of diagnosis was 6 years, nevertheless the median age at initial symptoms was 3 years. Thirteen patients (50%) were diagnosed before the age of 5 years. Two patients had no symptoms and were diagnosed while screening siblings of index patients. Seventeen patients (65.4%) had reached end-stage renal disease (ESRD): 6/17 (35.3%) during infancy, 4/17 (23.5%) in early childhood and 7/17 (41.29%) in late childhood. Two patients (7.7%) had clinically manifest extra renal (retina, heart, bone, soft tissue) involvement. Mutational analysis of AGXT gene confirmed the diagnosis of PH1 in 15 out of 19 patients (79%) where analysis had been performed. Fifty percent of patients with maintained renal functions had projected 10 years renal survival.

CONCLUSION

PH1 is a heterogeneous disease with wide spectrum of clinical, imaging and functional presentation. More than two-thirds of patients presented prior to the age of 5 years; half of them with the stormy course of infantile PH1. ESRD was the commonest presenting manifestation in two-thirds of our cohort.

Primary hyperoxaluria type 1 in 18 children: genotyping and outcome

Background. Primary hyperoxaluria belongs to a group of rare metabolic disorders with autosomal recessive inheritance. It results from genetic mutations of the AGXT gene, which is more common due to higher consanguinity rates in the developing countries. Clinical features at presentation are heterogeneous even in children from the same family; this study was conducted to determine the clinical characteristics, type of AGXT mutation, and outcome in children diagnosed with PH1 at a tertiary referral center in Oman. Method. Retrospective review of children diagnosed with PH1 at a tertiary hospital in Oman from 2000 to 2013. Result. Total of 18 children were identified. Females composed 61% of the children with median presentation age of 7 months. Severe renal failure was initial presentation in 39% and 22% presented with nephrocalcinosis and/or renal calculi. Family screening diagnosed 39% of patients. Fifty percent of the children underwent hemodialysis. 28% of children underwent organ transplantation. The most common mutation found in Omani children was c.33-34insC mutation in the AGXT gene. Conclusion. Due to consanguinity, PH1 is a common cause of ESRD in Omani children. Genetic testing is recommended to help in family counseling and helps in decreasing the incidence and disease burden; it also could be utilized for premarital screening.

Mutational analysis of AGXT in two Chinese families with primary hyperoxaluria type 1

Background

Primary hyperoxaluria type 1 is a rare autosomal recessive disease of glyoxylate metabolism caused by a defect in the liver-specific peroxisomal enzyme alanine:glyoxylate aminotransferase (AGT) that leads to hyperoxaluria, recurrent urolithiasis, and nephrocalcinosis.

Methods

Two unrelated patients with recurrent urolithiasis, along with members of their families, exhibited mutations in the AGXT gene by PCR direct sequencing.

Results

Two heterozygous mutations that predict truncated proteins, p.S81X and p.S275delinsRAfs, were identified in one patient. The p.S81X mutation is novel. Two heterozygous missense mutations, p.M1T and p.I202N, were detected in another patient but were not identified in her sibling. These four mutations were confirmed to be of paternal and maternal origin.

Conclusions

These are the first cases of primary hyperoxaluria type 1 to be diagnosed by clinical manifestations and AGXT gene mutations in mainland China. The novel p.S81X and p.I202N mutations detected in our study extend the spectrum of known AGXT gene mutations.