[Primary hyperoxaluria: A review]

Primary hyperoxaluria in adults and children: a nationwide cohort highlights a persistent diagnostic delay

Background

Primary hyperoxalurias (PH) are extremely rare genetic disorders characterized by clinical heterogeneity. Delay in diagnosing these conditions can have detrimental effects on patient outcomes. The primary objective of this study is to assess the current diagnostic delay for PH.

Methods

This nationwide, observational and retrospective study included patients who received a genetic diagnosis of PH types 1, 2 and 3 between 1 January 2015 and 31 December 2019. Diagnostic delay was defined as the duration between the onset of symptoms and the time of genetic diagnosis.

Results

A total of 52 patients (34 children and 18 adults) were included in the study, with 40 PH1 (77%), 3 PH2 (6%) and 9 PH3 (17%). At the time of diagnosis, 12 patients (23%) required dialysis. Among the PH1 patients, the predominant symptom at onset in adults was renal colic (79% of cases), whereas symptoms in children were more diverse (renal colic in 17% of cases). The diagnostic delay was significantly shorter in children compared with adults [median (interquartile range)]: 1.2 (0.1-3.0) versus 30 (17-36) years, respectively (P < .0001). RNA interference was utilized in 23 patients (58%). Five individuals (13%) underwent double liver-kidney transplantation, and five (13%) received isolated kidney transplantation, with lumasiran therapy in four patients. For PH2 and PH3 patients, the diagnostic delay ranges from 0 to 3 years, with renal colic as first symptom in 33% of cases.

Conclusion

This extensive and recent cohort of PH underscores the considerable delay in diagnosing PH, particularly in adults, even in a country with a dedicated organization for enhancing the overall management of rare diseases. These findings reinforce the imperative for increased awareness among relevant specialties regarding the evaluation of urolithiasis.

Primary Hyperoxaluria Type 1: Clinical, Paraclinical, and Evolutionary Aspects in Adults from One Nephrology Center

Introduction

Primary hyperoxaluria type 1 (PH1) is a rare and inherited condition of urolithiasis. The aim of our study was to analyze clinical, paraclinical, and evolutionary aspects of PH1 in adult patients in our Nephrology department.

Methods

We conducted a retrospective single-center study between 1990 and 2021. We collected patients followed for PH1 confirmed by genetic study and/or histopathological features of renal biopsy and morphoconstitutional analysis of the calculi.

Results

There were 25 patients with a gender ratio of 1.78. The median age at onset of symptoms was 18 years. A delay in diagnosis more than 10 years was noted in 13 cases. The genetic study found the I244T mutation in 17 cases and 33-34 InsC in 4 cases. A kidney biopsy was performed in 5 cases, on a native kidney in 4 cases and on a graft biopsy in one case. The analysis of calculi was done in 10 cases showing type Ic in 2 cases. After a median follow-up of 13 years (1 year-42 years), 14 patients progressed to end-stage chronic renal failure (ESRD). The univariate study demonstrated a remarkable association with progression to ESRD in our population (44% vs. 56%) RR = 13.32 (adjusted ORs (95% CI): 2.82-62.79) (p < 0.01).

Conclusion

Progression to ESRD was frequent in our series. Early diagnosis and adequate management can delay such an evolution.

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.

Medical Treatment and Prevention of Urinary Stone Disease

The pathophysiology underlying urinary stone formation remains an area of active investigation. There are many pharmacotherapies aimed at optimizing metabolic factors and reducing urinary supersaturation of stone components that play an important role in urinary stone prevention. In addition, medical expulsive therapy for ureteral stones and medical dissolution therapy for uric acid-based urinary stones are helpful treatment tools and are used alongside surgical treatments in the management of urinary stones.

Therapeutic RNA-silencing oligonucleotides in metabolic diseases

Recent years have seen unprecedented activity in the development of RNA-silencing oligonucleotide therapeutics for metabolic diseases. Improved oligonucleotide design and optimization of synthetic nucleic acid chemistry, in combination with the development of highly selective and efficient conjugate delivery technology platforms, have established and validated oligonucleotides as a new class of drugs. To date, there are five marketed oligonucleotide therapies, with many more in clinical studies, for both rare and common liver-driven metabolic diseases. Here, we provide an overview of recent developments in the field of oligonucleotide therapeutics in metabolism, review past and current clinical trials, and discuss ongoing challenges and possible future developments.

Inherited Neuromuscular Disorders: Which Role for Serum Biomarkers?

Inherited neuromuscular disorders (INMD) are a heterogeneous group of rare diseases that involve muscles, motor neurons, peripheral nerves or the neuromuscular junction. Several different lab abnormalities have been linked to INMD: sometimes they are typical of the disorder, but they usually appear to be less specific. Sometimes serum biomarkers can point out abnormalities in presymtomatic or otherwise asymptomatic patients (e.g., carriers). More often a biomarker of INMD is evaluated by multiple clinicians other than expert in NMD before the diagnosis, because of the multisystemic involvement in INMD. The authors performed a literature search on biomarkers in inherited neuromuscular disorders to provide a practical approach to the diagnosis and the correct management of INMD. A considerable number of biomarkers have been reported that support the diagnosis of INMD, but the role of an expert clinician is crucial. Hence, the complete knowledge of such abnormalities can accelerate the diagnostic workup supporting the referral to specialists in neuromuscular disorders.

Limited Treatment Options in Primary Hyperoxaluria with Renal Failure

Primary hyperoxaluria (PH) is a rare autosomal recessive metabolic disorder where serum oxalate levels rise due to overproduction. The kidney tubule is a main target for oxalate deposition, resulting in damage to the organ. Kidney failure is rare in these patients. We present a 67-year-old female with hemodialysis-dependent end-stage renal disease likely due to PH type 2 or 3. With extremely high levels of serum oxalate (60.4 μmol/L), this patient had minimal treatment options for her rare disease. This report details a unique presentation of a rare disease where kidney biopsy was instrumental.

Small interfering RNA from the lab discovery to patients' recovery

In 1998, the RNA interference discovery by Fire and Mello revolutionized the scientific and therapeutic world. They showed that small double-stranded RNAs, the siRNAs, were capable of selectively silencing the expression of a targeted gene by degrading its mRNA. Very quickly, it appeared that the use of this natural mechanism was an excellent way to develop new therapeutics, due to its specificity at low doses. However, one major hurdle lies in the delivery into the targeted cells, given that the different extracellular and intracellular barriers of the organism coupled with the physico-chemical characteristics of siRNA do not allow an efficient and safe administration. The development of nanotechnologies has made it possible to counteract these hurdles by vectorizing the siRNA in a vector composed of cationic lipids or polymers, or to chemically modify it by conjugation to a molecule. This has enabled the first clinical developments of siRNAs to begin very quickly after their discovery, for the treatment of various acquired or hereditary pathologies. In 2018, the first siRNA-containing drug was approved by the FDA and the EMA for the treatment of an inherited metabolic disease, the hereditary transthyretin amyloidosis. In this review, we discuss the different barriers to the siRNA after systemic administration and how vectorization or chemical modifications lead to avoid it. We describe some interesting clinical developments and finally, we present the future perspectives.

Metabolomic and lipidomic characterization of Oxalobacter formigenes strains HC1 and OxWR by UHPLC-HRMS

Diseases of oxalate, such as nephrolithiasis and primary hyperoxaluria, affect a significant portion of the US population and have limited treatment options. Oxalobacter formigenes, an obligate oxalotrophic bacterium in the mammalian intestine, has generated great interest as a potential probiotic or therapeutic treatment for oxalate-related conditions due to its ability to degrade both exogenous (dietary) and endogenous (metabolic) oxalate, lowering the risk of hyperoxaluria/hyperoxalemia. Although all oxalotrophs degrade dietary oxalate, Oxalobacter formigenes is the only species shown to initiate intestinal oxalate secretion to draw upon endogenous, circulating oxalate for consumption. Evidence suggests that Oxalobacter regulates oxalate transport proteins in the intestinal epithelium using an unidentified secreted bioactive compound, but the mechanism of this function remains elusive. It is essential to gain an understanding of the biochemical relationship between Oxalobacter and the host intestinal epithelium for this microbe to progress as a potential remedy for oxalate diseases. This investigation includes the first profiling of the metabolome and lipidome of Oxalobacter formigenes, specifically the human strain HC1 and rat strain OxWR, the only two strains shown thus far to initiate net intestinal oxalate secretion across native gut epithelia. This study was performed using untargeted and targeted metabolomics and lipidomics methodologies utilizing ultra-high-performance liquid chromatography-mass spectrometry. We report our findings that the metabolic profiles of these strains, although largely conserved, show significant differences in their expression of many compounds. Several strain-specific features were also detected. Discussed are trends in the whole metabolic profile as well as in individual features, both identified and unidentified. Graphical abstract ᅟ.

An Angiotensinogen Gene Polymorphism (rs5050) Is Associated with the Risk of Coronary Artery Aneurysm in Southern Chinese Children with Kawasaki Disease

Background

Kawasaki disease (KD) is an acute vasculitis disease that commonly causes acquired heart disease in children. Coronary artery aneurysm (CAA) is a major complication of KD. However, the pathogenesis of KD remains unclear. The results of a genome-wide association study (GWAS) showed that two functional single-nucleotide polymorphisms (SNPs; rs699A>G and rs5050T>G) in the angiotensinogen (AGT) gene were related to cardiovascular disease susceptibility. The purpose of our study was to estimate the relationship between the two GWAS-identified AGT gene polymorphisms and the risk of CAA in Southern Chinese children with KD.

Methods

We genotyped the two AGT gene polymorphisms (rs699A>G and rs5050T>G) in 760 KD cases and 972 healthy controls. We used the odds ratios (ORs) and 95% confidence intervals (CIs) to estimate the degree of the associations.

Results

These two AGT gene polymorphisms were not associated with a risk of KD relative to the controls, but after adjusting for sex and age, the carriers of the rs5050G allele with TG/GG vs TT had an adjusted OR = 1.56, 95% CI = 1.01-2.41, and P = 0.044 relative to the carriers of the rs5050TT genotype. The susceptibility to CAA was more predominant in KD patients younger than 12 months old.

Conclusions

Our results indicate that the AGT gene polymorphism rs5050T>G may increase the risk of CAA in children with KD, especially those who are younger than 12 months. These results need to be verified by a validation study with a larger sample size.

Imaging features of primary hyperoxaluria

Primary hyperoxaluria (PH) is a group of autosomal recessive diseases that affect the metabolism of glyoxalate and oxalate. As a result of the enzymatic deficiency, there is overproduction and urinary excretion of oxalate with progressive renal damage and subsequent deposition of oxalate salts in various tissues. The definitive treatment in cases of end-stage kidney disease is a combined liver and kidney transplant. Imaging features are diverse and reflect the multiple organs that might be affected. These include nephrolithiasis and nephrocalcinosis, oxalate osteopathy, as well as other findings, such as splenomegaly and oxalate deposition in the heart. In this review article, we present various imaging findings that may appear in patients with PH.