Advances in the gene therapy of primary hyperoxaluria / 中华泌尿外科杂志

Primary hyperoxaluria (PH) is a rare autosomal recessive hereditary disease, characterized by calcium oxalate kidney stone and nephrocalcinosis caused by defects in enzymes of liver glyoxylate metabolism. Up to now, treatment options for PH are limited. Although medication treatment and liver transplantation can slow down the progression and mitigate the symptoms, the evidence for them turned out to be weak. In recent years, breakthroughs in biotechnology provide novel promising directions for drug development. Small interfering RNA drugs, such as lumasiran and nedosiran, selectively reduce hepatic expression of glycolate oxidase and lactate dehydrogenase respectively, reducing hepatic oxalate production and urinary oxalate levels in PH patients. Gene-editing, such as CRISPR/Cas9, will be a potential treatment method of PH. This review encompasses recent developments in the gene therapy of PH.

Clinical analysis of seven cases with primary hyperoxaluria type 1 in children / 中华儿科杂志

Objective@#To investigate the clinical, imaging and molecular characteristics of primary hyperoxaluria type 1 (PH1) in children and to sum up existing evidence for further understanding the phenotype-genotype correlation of infantile PH1.@*Methods@#This retrospective analysis was based on the medical records of children with PH1 diagnosed by gene test in the Department of Nephrology, Guangzhou Women and Children′s Medical Center from June 2016 to May 2019. Targeted exome sequencing was performed on tubular disease-related genes of the probands and Sanger sequencing was conducted to validate suspected pathogenic variants of family members. Logistic regression analysis of NC and CCr was adopted to show the relation between NC and renal function. The literature review was conducted, and the clinical, imaging and molecular biogenetic characteristics of the disease were analyzed and summarized.@*Results@#A total of 7 children from 6 families were enrolled. The median age of onset was 5 months. The median age of diagnosis was 8 months. Five cases had progressed to end-stage renal disease (ESRD), one case had chronic kidney disease (CKD) stage 1, and the other one had CKD stage 2. Four cases died, one case maintained on hemodialysis, and the other two non-dialysis cases were followed up. Among the 7 cases, 4 patients had infantile PH1, 1 patient had child and adolescent type, 1 patient had family type and the other one had unknown classification. There were two siblings (the younger brother had uremia and the sister had normal renal function) who had the delayed diagnosis for 5 and 3 years respectively. All patients in this cohort had proteinuria and microscopic hematuria, but no patients had gross hematuria. Three cases had hypercalciuria. Comprehensive diagnostic imaging evaluation include CT scan, MR scan, radiography and ultrasound led to the diagnosis of nephrocalcinosis (NC) in 5 cases, including 4 cases of simple NL and 1 case of NC with nephrolithiasis (NL), 1 case of multiple NL and 1 case of microcrystal deposition in renal medulla. However, only one case of NC was identified by ultrasound, the other 4 cases of NC were identified by radiograph examination. In the logistic regression analysis involving NC and creatinine clearnce rate (CCr), the results showed that NC was an independent risk factor for renal dysfunction (OR 2.5, 95%CI 0.7-1.2, P<0.05). All the 7 cases had AGXT gene variant, including homozygous variant in 4 cases and compound heterozygous variant in 3 cases. A total of 9 variant genotypes were found, and exon 6 variants were found in 4 children. Among them, there were 3 cases with c.679_680delAA. To our knowledge, both c.679_680delAA and c.190A>T in the cohort have not been reported previously.@*Conclusions@#Infantile PH1 is the most common type of PH1 in children, which progresses rapidly or even begins with renal failure, with poor prognosis. It is also highly heterogeneous in phenotype and genotype. NC is an independent risk factor leading to renal failure. Radiograph examination showed high specificity for the diagnosis of NC. At present, the misdiagnosis and delayed diagnosis of PH1 are still common in China. It is of great significance to carry out quantitative determination of uric oxalate in order to reduce the misdiagnosis rate and enhance follow-up technologies for evaluating the therapeutic effect.

Primary hiperoxaluria diagnosed after kidney transplantation: report of 2 cases and literature review / Hiperoxalúria primária diagnosticada após transplante renal: relato de dois casos e revisão da literatura

Abstract Primary hyperoxaluria (PH) is a very rare genetic disorder; it is characterized by total or partial deficiency of the enzymes related to the metabolism of glyoxylate, with an overproduction of calcium oxalate that is deposited in different organs, mainly the kidney, leading to recurrent lithiasis, nephrocalcinosis and end stage renal disease (ESRD). In patients with ESRD that receive kidney transplantation alone, the disease has a relapse of 100%, with graft loss in a high percentage of patients in the first 5 years of transplantation. Three molecular disorders have been described in PH: mutation of the gene alanin glioxalate aminotransferase (AGXT); glyoxalate reductase/hydroxy pyruvate reductase (GRHPR) and 4-OH-2-oxoglutarate aldolase (HOGA1). We present two cases of patients with a history of renal lithiasis who were diagnosed with primary hyperoxaluria in the post-transplant period, manifested by early graft failure, with evidence of calcium oxalate crystals in renal biopsy, hyperoxaluria, hyperoxalemia, and genetic test compatible; they were managed with proper diet, abundant oral liquids, pyridoxine, hydrochlorothiazide and potassium citrate; however, they had slow but progressive deterioration of their grafts function until they reached end-stage chronic renal disease.

Resumo A hiperoxalúria primária (HP) é um distúrbio genético muito raro, caracterizado por deficiência total ou parcial das enzimas relacionadas ao metabolismo do glioxilato, superprodução de oxalato de cálcio que se deposita em vários órgãos (principalmente os rins) resultando em litíase recorrente, nefrocalcinose e doença renal terminal (DRT). Nos pacientes com DRT que recebem transplante renal, a doença apresenta recidiva em 100% dos casos, com perda do enxerto nos primeiros cinco anos após o transplante num elevado percentual de pacientes. Três distúrbios moleculares foram descritos na HP: mutação dos genes da alanina-glioxilato aminotransferase (AGXT), glioxilato redutase/hidroxipiruvato redutase (GRHPR) e 4-OH-2-oxoglutarato aldolase (HOGA1). Apresentamos dois casos de pacientes com histórico de litíase renal diagnosticados com hiperoxalúria primária no período pós-transplante, manifestada na forma de perda precoce do enxerto com evidências de cristais de oxalato de cálcio na biópsia renal, hiperoxalúria, hiperoxalemia e testes genéticos compatíveis. Os pacientes foram tratados com abordagem nutricional, líquidos orais em abundância, piridoxina, hidroclorotiazida e citrato de potássio. Contudo, os pacientes apresentaram deterioração lenta e gradual da função do enxerto e evoluíram para doença renal terminal.

Analysis of mutant genes in a primary hyperoxaluria type Ⅲ family / 中华肾脏病杂志

Objective To describe the clinical characteristics of one child with primary hyperoxaluria types Ⅲ, and to analyze the potential mutant genes in his family.Methods AGXT, GRHPR and HOGA1 genes were analyzed by direct sequencing analysis in this family.One hundred unrelated healthy subjects were also analyzed as controls.Results The child had early onset of symptoms (0.8 year).His principal clinical manifestation included nephrolithiasis and obstructive nephropathy, however his nephrocalcinosis was mild.And he presented high urine oxalate, high urine calcium, and lower citrate levels.Two novel heterozygous mutations in HOGA1 were identified (compound heterozygous), one mutation was a 2-bp substitution at the last position in exon 6 and the first position of intron 6 respectively (c.834_834 + 1GG ＞ TT);another was a guanine to adenine substitution of the last nucleotide of exon 6 (c.834G ＞ A).Both of these variants found in this study probably acted as splicing mutations.Direct sequencing analysis failed to find these mutations in 100 unrelated healthy subjects.In addition, a SNP (c.715G ＞ A, p.V239I) was found in this family.There were no mutations detected in AGXT and GRHPR.Conclusions Two novel mutations are identified probably in association with PH Ⅲ.This is the first description and investigation on mutant gene analysis of PHⅢ in Asia.

Analysis of AGXT gene mutation in a primary hyperoxaluria type Ⅰ family / 中华肾脏病杂志

Objective To describe the clinical characteristics,and to analyze the AGXT gene mutation in three siblings with primary hyperoxaluria type I (PHI).Methods AGXT gene mutation was analyzed by direct sequencing analysis in this family,and the minor allele status was also tested.One hundred unrelated healthy subjects were also analyzed as controls.Results Three mutations in AGXT were identified in each of three patients including two novel heterozygous missense mutations and one previously reported variant.One mutation was a methionine to leucine substitution at position 49 (p.M49L,c.145A ＞ C) in exon 1,one was an asparagine to isoleucine transition at codon 72 (p.N72I,c.215A ＞ T) in exon 2,and another was a heterozygous nonsense mutation at codon 333 (p.R333*).Both p.M49L and p.R333* occured in cis configuration with the minor allele IVS1 +74 bp.Conclusions Two novel mutations are identified probably in association with PHI,however their pathogenicity and potential molecular mechanisms should be explored by further investigations.This is the first investigation on mutant gene analysis of PHI in China.

Hiperoxaluria primaria en tres hermanos / Primary hyperoxaluria in three brothers

La hiperoxaluria es responsable de 2%-20% de las causas metabólicas de litiasis en niños y adolescentes. Esta puede ser secundaria o primaria(HP), en este último caso es tipo I o tipo II, de herencia autosómica recesiva. El objetivo es analizar diagnóstico y evolución en dos hermanos con HP tipo I y un tercero con alta probabilidad. El primer caso presentó a los 9 años un cólico nefrítico con litiasis múltiples bilaterales y una IRA leve. Presentaba hiperoxaluria de 214 mg/1,73 m2. Se descartaron causas secundarias. El estudio genético demostró dos copias de la mutación IIe244Thr. Los otros dos pacientes se presentaron en forma similar, a edades de 8 y 17 años. La piridoxina a altas dosis descendió los niveles de oxaluria como está descrito en un tercio de los casos. El tiempo de evolución es 7,3 y 1 año respectivamente. Persisten actualmente con litiasis bilaterales, sin nefrocalcinosis ni alteraciones del medio interno. La severidad de la HP tipo I es variable, hay formas de presentación temprana con litiasis recurrente y falla renal crónica en la infancia o en la adolescencia; otras de inicio tardío en edad adulta. Se trata de una enfermedad grave, progresiva, cuyo diagnóstico temprano con estudio metabólico completo puede mejorar el pronóstico,fundamentalmente en aquellos que responden a la piridoxina. El manejo de la litiasis y sus complicaciones es fundamental para evitar la IRC. Cuando ésta se desarrolla, la diálisis agresiva y el trasplante hepatorrenal son las opciones terapéuticas. Es el primer informe de casos confirmados de hiperoxaluria primaria en nuestro país...