Clinical analysis of 13 children with primary hyperoxaluria type 1

Spinal Cord Compression as the First Presentation of Primary Hyperoxaluria in a Patient With Kidney Failure: A Case Report and Literature Review

A 50-year-old woman with kidney failure complained of back pain and an inability to walk. The medical history included hypothyroidism, nephrolithiasis, and resistant anemia aligned with several transfusions. The examination showed hepatosplenomegaly, lower limb weakness, absence of reflexes, and lack of sensations with a sensory level T6. Laboratory results showed hypercalcemia with suppression of parathyroid hormone levels. Magnetic resonance imaging showed vertebral fractures and mass-like lesions that compressed the spine at T4, T9, L4, and L5. Vertebral and bone marrow biopsies showed calcium oxalate (CaOx) depositions. Here, we reported a rare case of primary hyperoxaluria (PH) in a patient with kidney failure who presented with spinal cord compression caused by vertebral fractures and mass-like lesions. We summarized a literature review of PH patients with spinal cord compression, which showed only 3 cases. The multiorgan CaOx infiltration in this patient also caused resistant anemia, hepatosplenomegaly, extensive bone lesions, hypoparathyroidism, hypothyroidism, and hypercalcemia. The overdiagnosis of renal osteodystrophy and the negative family history could delay the diagnosis of PH in patients with kidney failure. Thus, clinicians should always consider PH in the differential diagnosis of kidney failure patients with stone events given that the early diagnosis of PH could be lifesaving.

Biallelic Variant in the AGXT Gene in a Family Segregating Primary Hyperoxaluria; Accurate Genetic Diagnosis and Carrier Detection

AIM

Autosomal recessive primary hyperoxalurias (PH) are genetic disorders characterised by elevated oxalate production. Mutations in genes involved in glycoxylate metabolism are the underlying cause of PH. Type 1 PH (PH1) results in malfunctioning of alanine-glyoxylate aminotransferase enzymes of liver due to a change in the genetic sequence of alanine-glyoxylate aminotransferase (AGXT) gene. We encountered a large family segregating genetic disease of high oxalate kidney stones. A genetic analysis was carried out with the aim to identify underlying genetic defect.

METHODS

A large family with multiple affected individuals was recruited for this study. An extensive clinical evaluation, followed by genetic analysis, was carried out. Due to the heterogeneous nature of the disease, two members of the family having disease symptoms were subjected to whole exome sequencing (WES). Variants were annotated, filtered, and prioritised using various bioinformatic tools to detect disease associated genetic defects.

RESULTS

Unbiased and hypothesis-free WES data analysis was performed. Raw reads (fastq files) were mapped to the reference genome and duplicates were removed. Variants were annotated, filtered, and prioritised. A low-frequency missense variant (c. 1049G>A) in the AGXT gene was considered the candidate variant. This variant replaces the highly conserved glycine amino acid with aspartate (p.Gly350Asp). The variant is destabilising for protein-protein interaction based on predicted change in binding free energy (ΔΔG). All members having disease phenotype were found homozygous to the mutation. Both parents and unaffected individuals in a family are heterozygous for the variant.

CONCLUSION

Identification of pathogenic variant in the AGXT gene, in this family, provides genotype-phenotype correlation and permits accurate clinical diagnosis as well as carrier detection. Moreover, this variant extends the AGXT mutation spectrum in a different population and highlights the clinical significance and diagnostic relevance of the variant.

Hot Hearts on Bone Scintigraphy Are Not All Amyloidosis: Hyperoxaluria-Associated Cardiomyopathy

ABSTRACT

A 54-year-old woman with a history of end-stage renal disease was found to have infiltrative cardiomyopathy by echocardiography. 99m Tc-pyrophosphate ( 99m Tc-PYP) scintigraphy was positive with a remarkable myocardial uptake. Gene test found a mutation of AGXT , confirming a final diagnosis of primary hyperoxaluria. Radiotracer uptake was due to high myocardial oxalate deposition. This case illustrates false positivity of the 99m Tc-PYP scan caused by hyperoxaluria-associated cardiomyopathy, which raises awareness for other conditions apart from amyloid cardiomyopathy.

Mutation Characteristics of Primary Hyperoxaluria in the Chinese Population and Current International Diagnosis and Treatment Status

Background

Primary hyperoxaluria (PH) is a rare autosomal recessive disorder, mainly due to the increase in endogenous oxalate production, causing a series of clinical features such as kidney stones, nephrocalcinosis, progressive impairment of renal function, and systemic oxalosis. There are three common genetic causes of glycolate metabolism anomalies. Among them, PH type 1 is the most prevalent and severe type, and early end-stage renal failure often occurs.

Summary

This review summarizes PH through pathophysiology, genotype, clinical manifestation, diagnosis, and treatment options. And explore the characteristics of Chinese PH patients.

Key Messages

Diagnosis of this rare disease is based on clinical symptoms, urinary or blood oxalate concentrations, liver biopsy, and genetic testing. Currently, the main treatment is massive hydration, citrate inhibition of crystallization, dialysis, liver and kidney transplantation, and pyridoxine. Recently, RNA interference drugs have also been used. In addition, technologies such as gene editing and autologous liver cell transplantation are also being developed. C.815_816insGA and c.33_34insC mutation in the AGXT gene could be a common variant in Chinese PH1 population. Mutations at the end of exon 6 account for approximately 50% of all Chinese HOGA1 mutations. Currently, the treatment of PH in China still relies mainly on symptomatic and high-throughput dialysis, with poor prognosis (especially for PH1 patients).

Comprehensive evaluation of patients with primary hyperoxaluria type 1: A nationwide study

BACKGROUND

Primary hyperoxaluria type 1 (PH1) is characterized by increased endogenous oxalate production and deposition as calcium oxalate crystals. The main manifestations are nephrocalcinosis/nephrolithiasis, causing impaired kidney function. We aimed to evaluate the clinical characteristics and overall outcomes of paediatric PH1 patients in Turkey.

METHODS

This is a nationwide, multicentre, retrospective study evaluating all available paediatric PH1 patients from 15 different paediatric nephrology centres in Turkey. Detailed patient data was collected which included demographic, clinical and laboratory features. Patients were classified according to their age and characteristics at presentation: patients presenting in the first year of life with nephrocalcinosis/nephrolithiasis (infantile oxalosis, Group 1), cases with recurrent nephrolithiasis diagnosed during childhood (childhood-onset PH1, Group 2), and asymptomatic children diagnosed with family screening (Group 3).

RESULTS

Forty-eight patients had a mutation consistent with PH1. The most common mutation was c.971_972delTG (25%). Infantile oxalosis patients had more advanced chronic kidney disease (CKD) or kidney failure necessitating dialysis (76.9% vs. 45.5%). These patients had much worse clinical course and mortality rates seemed to be higher (23.1% vs. 13.6%). Patients with fatal outcomes were the ones with significant comorbidities, especially with cardiovascular involvement. Patients in Group 3 were followed with better outcomes, with no kidney failure or mortality.

CONCLUSION

PH1 is not an isolated kidney disease but a systemic disease. Family screening helps to preserve kidney function and prevent systemic complications. Despite all efforts made with traditional treatment methods including transplantation, our results show devastating outcomes or mortality.

Identification of mutations in 15 nephrolithiasis-related genes leading to a molecular diagnosis in 85 Chinese pediatric patients

BACKGROUND

The aim of this study was to describe the genotypic and phenotypic characteristics of Chinese pediatric patients with hereditary nephrolithiasis.

METHODS

Whole-exome sequencing (WES) was performed on 218 Chinese pediatric patients with kidney stones, and genetic and clinical data were collected and analyzed retrospectively.

RESULTS

The median age at onset in our cohort was 2.5 years (age range, 0.3-13 years). We detected 79 causative mutations in 15 genes, leading to a molecular diagnosis in 38.99% (85/218) of all cases. Monogenic mutations were present in 80 cases, and digenic mutations were present in 5 cases; 34.18% (27/79) of mutations were not included in the databases. Six common mutant genes, i.e., HOGA1, AGXT, GRHPR, SLC3A1, SLC7A9, and SLC4A1, were found in 84.71% of the patients overall. Furthermore, three mutations (A278A, c.834_834 + 1GG > TT, and C257G) in HOGA1, two mutations (K12QfX156 and S275RfX28) in AGXT, and one mutation (C289DfX22) in GRHPR represented hotspot mutations. The patients with HOGA1 mutations had the earliest onset age (0.8 years), followed by those with SLC7A9 (1.8 years), SLC4A1 (2.7 years), AGXT (4.3 years), SLC3A1 (4.8 years), and GRHPR (8 years) mutations (p = 0.002). Nephrocalcinosis was most commonly observed in patients with AGXT gene mutations.

CONCLUSIONS

Fifteen causative genes were detected in 85 Chinese pediatric patients with kidney stone diseases. The most common mutant genes, novel mutations, hotspot mutations, and genotype-phenotype correlations were also found. This study contributes to the understanding of genetic profiles and clinical courses in pediatric patients with hereditary nephrolithiasis. A higher resolution version of the Graphical abstract is available as Supplementary information.

Case series and literature review of primary hyperoxaluria type 1 in Chinese patients

Based on the single-center case reports and all reported patients with primary hyperoxaluria type 1 (PH1) in China, this study discussed the clinical and genetic characteristics of this disease retrospectively. We reported and validated a novel genetic variation c.302 T > G: the clinical phenotypes of the two siblings were similar, in which both had onset in infancy, mainly manifested as renal insufficiency, and died within 6 months out of end-stage renal disease. The literature review is the first to summarize the Chinese patients with PH1 up to now. Forty-eight Chinese patients were included, containing 7 adults and 41 children. The median onset age was 51 months, and the ratio of male to female was 2.69:1. It showed a poor prognosis: 51.1% of Chinese primary hyperoxaluria type 1 patients suffered from end-stage renal disease, and 38.9% of patients died. Urolithiasis was the most common clinical manifestation both in adults and children, while infant-onset patients generally presented with renal insufficiency and had a higher mortality of 75.0%. One hundred and forty-nine AGXT mutant alleles are currently known in the Chinese population, c.33dupC and c.815_816insGA were the most common AGXT genes, accounting for 12.0% and 10.1% of allele frequencies, respectively. The exons 1, 2, 6, and 8 were the most common locations of gene variants, accounting for 78% of all variants, which will be promising targets of DNA sequencing for primary hyperoxaluria type 1.

A Rare Sparkle: A Case of Calcified Kidneys in a Young Infant With Renal Failure

Primary hyperoxaluria-1 (PH1) is an autosomal recessively inherited rare genetic condition due to the deficiency of the hepatic enzyme alanine:glyoxylate aminotransferase which leads to high systemic levels of oxalate and subsequently, early end-stage renal disease and death. Here, we present a case of a three-month-old male infant who presented with loose stools, reduced oral intake, and decreased activity for 12-13 days along with edema and a peeling rash on cheeks, lips, and genitalia. During the entire duration of the inpatient stay, the child was oligoanuric. Kidney ultrasound (USG) was suggestive of bilateral hyperechoic kidneys with increased cortical echogenicity and a computed tomography scan showed bilateral diffusely calcified renal cortices with well-preserved renal architecture. A diagnosis of "oxalate nephropathy" was made from renal biopsy and genetic testing confirmed it to be "primary hyperoxaluria-1". The child was initially managed conservatively, and then peritoneal dialysis was done, following which the child was shifted to intermittent hemodialysis.

Genotype and Phenotype Characteristics of Chinese Pediatric Patients with Primary Hyperoxaluria

Primary hyperoxaluria (PH) is a rare monogenic disorder characterized by recurrent kidney stones, nephrocalcinosis, and renal impairment. To study the genotype and phenotype characteristics, we evaluated the clinical data of 42 Chinese pediatric PH patients who were diagnosed from May 2016 to April 2022. We found that patients with the PH3 type showed an earlier age of onset than those with the PH1 and PH2 types (1 versus 5 and 8 years, respectively, P < 0.001). Urine citrate was significantly lower in PH1 and PH2 patients than that in PH3 patients (91.81 and 85.56 versus 163.9 μg/mg, respectively, P = 0.044). Spot urine oxalate levels were slightly higher in PH1 than that in PH2 and PH3 patients (457.9 versus 182.38 and 309.14 μg/mg, respectively, P = 0.189). A significant negative correlation between the urine calcium/creatinine ratio and the oxalate/creatinine ratio was observed in the entire PH cohort (r = -0.360, P = 0.04) and the PH3 cohort (r = -0.674, P = 0.003). PH-causative genes showed hotspot mutations or regions, including c.815_816insGA and c.33dup in AGXT, 864_865del in GRHPR, and exon 6 skipping and c.769T>G in HOGA1. In the PH1 cohort, the estimated glomerular filtration rate (eGFR) was lowest in patients with heterozygous c.33dup. In the PH3 cohort, patients with heterozygous exon 6 skipping presented the lowest eGFR and a significant decrease in the renal survival advantage. In summary, PH1 patients exhibit much more severe phenotypes than those with other types. Hotspot mutations or regions exist in patients with all types of PH and show differences among ethnicities. Genotype-phenotype correlations are observed in PH1 and PH3.

Four novel variants identified in primary hyperoxaluria and genotypic and phenotypic analysis in 21 Chinese patients

Background: Primary hyperoxaluria (PH) is a rare genetic disorder characterized by excessive accumulation of oxalate in plasma and urine, resulting in various phenotypes due to allelic and clinical heterogeneity. This study aimed to analyze the genotype of 21 Chinese patients with primary hyperoxaluria (PH) and explore their correlations between genotype and phenotype. Methods: Combined with clinical phenotypic and genetic analysis, we identified 21 PH patients from highly suspected Chinese patients. The clinical, biochemical, and genetic data of the 21 patients were subsequently reviewed. Results: We reported 21 cases of PH in China, including 12 cases of PH1, 3 cases of PH2 and 6 cases of PH3, and identified 2 novel variants (c.632T > G and c.823_824del) in AGXT gene and 2 novel variants (c.258_272del and c.866-34_866-8del) in GRHPR gene, respectively. A possible PH3 hotspot variant c.769T > G was identified for the first time. In addition, patients with PH1 showed higher levels of creatinine and lower eGFR than those with PH2 and PH3. In PH1, patients with severe variants in both alleles had significantly higher creatinine and lower eGFR than other patients. Delayed diagnosis still existed in some late-onset patients. Of all cases, 6 had reached to end-stage kidney disease (ESKD) at diagnosis with systemic oxalosis. Five patients were on dialysis and three had undergone kidney or liver transplants. Notably, four patients showed a favorable therapeutic response to vitamin B6, and c.823_824dup and c.145A > C may be identified as potentially vitamin B6-sensitive genotypes. Conclusion: In brief, our study identified 4 novel variants and extended the variant spectrum of PH in the Chinese population. The clinical phenotype was characterized by large heterogeneity, which may be determined by genotype and a variety of other factors. We first reported two variants that may be sensitive to vitamin B6 therapy in Chinese population, providing valuable references for clinical treatment. In addition, early screening and prognosis of PH should be given more attention. We propose to establish a large-scale registration system for rare genetic diseases in China and call for more attention on rare kidney genetic diseases.