Cystinuria: an update on pathophysiology, genetics, and clinical management.

Cystinuria is the most common genetic cause of nephrolithiasis in children. It is considered a heritable aminoaciduria as the genetic defect affects the reabsorption of cystine and three other amino acids (ornithine, lysine, and arginine) in the renal proximal tubule. Patients affected by this condition have elevated excretion of cystine in the urine, and because of this amino acid's low solubility at normal urine pH, patients tend to form cystine calculi. To date, two genes have been identified as disease-causative: SLC3A1 and SLC7A9, encoding for the two subunits of the heterodimeric transporter. The clinical features of this condition are solely related to nephrolithiasis. The diagnosis is usually made during infancy or adolescence, but cases of late diagnosis are common. The goal of therapy is to reduce excretion and increase the solubility of cystine, through both modifications of dietary habits and pharmacological treatment. However, therapeutic interventions are not always sufficient, and patients often have to undergo several surgical procedures during their lives to treat recurrent nephrolithiasis. The goal of this literature review is to synthesize the available evidence on diagnosis and management of patients affected by cystinuria in order to provide physicians with a practical tool that can be used in daily clinical practice. This review also aims to shed some light on new therapy directions with the aim of ameliorating kidney outcomes while improving adherence to treatment and quality of life of cystinuric patients.

Results of a Gene Panel Approach in a Cohort of Patients with Incomplete Distal Renal Tubular Acidosis and Nephrolithiasis.

BACKGROUND: Distal renal tubular acidosis (dRTA) is characterized by an impairment of urinary acidification resulting in metabolic acidosis, hypokalemia, and inappropriately elevated urine pH. If not treated, this chronic condition eventually leads to nephrocalcinosis, nephrolithiasis, impaired renal function, and bone demineralization. dRTA is a well-defined entity that can be diagnosed by genetic testing of 5 genes known to be disease-causative. Incomplete dRTA (idRTA) is defined as impaired urinary acidification that does not lead to overt metabolic acidosis and therefore can be diagnosed if patients fail to adequately acidify urine after an ammonium chloride (NH4Cl) challenge or furosemide and fludrocortisone test. It is still uncertain whether idRTA represents a distinct entity or is part of the dRTA spectrum and whether it is caused by mutations in the same genes of overt dRTA. METHODS: In this cross-sectional study, we investigated a group of 22 stone formers whose clinical features were suspicious of idRTA. They underwent an NH4Cl challenge and were found to have impaired urinary acidification ability. These patients were then analyzed by genetic testing with sequencing of 5 genes: SLC4A1, ATP6V1B1, ATP6V0A4, FOXI1, and WDR72. RESULTS: Two unrelated individuals were found to have two different variants in SLC4A1 that had never been described before. CONCLUSIONS: Our results suggest the involvement of other genes or nongenetic tubular dysfunction in the pathogenesis of idRTA in stone formers. However, genetic testing may represent a cost-effective tool to recognize, treat, and prevent complications in these patients.

COVID-19 pandemic, the scarcity of medical resources, community-centred medicine and discrimination against persons with disabilities.

This research aims to examine access to medical treatment during the COVID-19 pandemic for people living with disabilities. During the COVID-19 pandemic, the practical and ethical problems of allocating limited medical resources such as intensive care unit beds and ventilators became critical. Although different countries have proposed different guidelines to manage this emergency, these proposed criteria do not sufficiently consider people living with disabilities. People living with disabilities are therefore at a higher risk of exclusion from medical treatments as physicians tend to assume they have poor quality of life, whereas access to medical treatment should be based on several parameters, including clinical data and prognosis. However, the COVID-19 pandemic shifts the medical paradigm from person-centred medicine to community-centred medicine, challenging the main ethical theories. We reviewed the main guidelines and recommendations for resources allocation and examined their position toward persons with disabilities. Based on our findings, we propose criteria for not discriminating against people with disabilities in allocating resources. The shift from person-centred to community-centred medicine offers opportunities but also risks sacrificing the most vulnerable people. The principle of reasonable accommodation must always be considered to guarantee the rights of persons with disabilities.

A female patient with Dent disease due to skewed X-chromosome inactivation.

X-linked proximal tubulopathies are rare diseases that predominantly affect men. Women are generally carriers and clinical or biochemical manifestations are usually absent or mild. We present the case of a young woman who presented with a full phenotype of Dent disease type 1 due to a de novo mutation in the CLCN5 gene and a skewed X-chromosome inactivation. Although cases of overt Dent disease type 2 and Lowe syndrome in women have been described in the literature, to our knowledge this is the first case of overt Dent disease type 1.

Bone mineral density assessment in patients with cystinuria.

BACKGROUND: Cystinuria is a rare genetic disease characterized by impaired tubular transport of cystine. Clinical features of cystinuria mainly include nephrolithiasis and its complications, although cystinuric patients may present with other comorbidities. There are currently no data on bone features of patients with cystinuria. Our aim is to characterize bone mineral density (BMD) in cystinuria. METHODS: Our study included adult cystinuric patients with estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m2 followed at 3 specialized outpatient clinics in Italy (Rome, Naples and Verona). Markers of bone turnover were analyzed in a centralized laboratory. Clinical, biochemical and dual-energy X-ray absorptiometry (DEXA) data were collected from September 2021 to December 2022. Linear regression models were used to evaluate statistically significant deviations from zero of Z-scores. RESULTS: Twenty-seven patients were included in the study. Mean (SD) age was 37 (15) years, 41% were women. Mean estimated glomerular filtration rate was 99 mL/min/1.73 m2. Serum parameters associated with bone turnover (parathyroid hormone, FGF23, calcium and phosphate) were all in the normal range, with only 4 patients showing mild hypophosphatemia. Prevalence of low bone mineral density, defined as Z-score ≤ - 2 at any site, was 15%. Average Z-scores were negative across most sites. CONCLUSIONS: Our study suggests that cystinuric patients have lower bone mineral density compared with individuals of the same sex and age, even when their kidney function is normal.

Cosmic kidney disease: an integrated pan-omic, physiological and morphological study into spaceflight-induced renal dysfunction.

Missions into Deep Space are planned this decade. Yet the health consequences of exposure to microgravity and galactic cosmic radiation (GCR) over years-long missions on indispensable visceral organs such as the kidney are largely unexplored. We performed biomolecular (epigenomic, transcriptomic, proteomic, epiproteomic, metabolomic, metagenomic), clinical chemistry (electrolytes, endocrinology, biochemistry) and morphometry (histology, 3D imaging, miRNA-ISH, tissue weights) analyses using samples and datasets available from 11 spaceflight-exposed mouse and 5 human, 1 simulated microgravity rat and 4 simulated GCR-exposed mouse missions. We found that spaceflight induces: 1) renal transporter dephosphorylation which may indicate astronauts' increased risk of nephrolithiasis is in part a primary renal phenomenon rather than solely a secondary consequence of bone loss; 2) remodelling of the nephron that results in expansion of distal convoluted tubule size but loss of overall tubule density; 3) renal damage and dysfunction when exposed to a Mars roundtrip dose-equivalent of simulated GCR.

Determinants of Kidney Failure in Primary Hyperoxaluria Type 1: Findings of the European Hyperoxaluria Consortium.

Introduction: Primary hyperoxaluria type 1 (PH1) has a highly heterogeneous disease course. Apart from the c.508G>A (p.Gly170Arg) AGXT variant, which imparts a relatively favorable outcome, little is known about determinants of kidney failure. Identifying these is crucial for disease management, especially in this era of new therapies. Methods: In this retrospective study of 932 patients with PH1 included in the OxalEurope registry, we analyzed genotype-phenotype correlations as well as the impact of nephrocalcinosis, urolithiasis, and urinary oxalate and glycolate excretion on the development of kidney failure, using survival and mixed model analyses. Results: The risk of developing kidney failure was the highest for 175 vitamin-B6 unresponsive ("null") homozygotes and lowest for 155 patients with c.508G>A and c.454T>A (p.Phe152Ile) variants, with a median age of onset of kidney failure of 7.8 and 31.8 years, respectively. Fifty patients with c.731T>C (p.Ile244Thr) homozygote variants had better kidney survival than null homozygotes (P = 0.003). Poor outcomes were found in patients with other potentially vitamin B6-responsive variants. Nephrocalcinosis increased the risk of kidney failure significantly (hazard ratio [HR] 3.17 [2.03-4.94], P < 0.001). Urinary oxalate and glycolate measurements were available in 620 and 579 twenty-four-hour urine collections from 117 and 87 patients, respectively. Urinary oxalate excretion, unlike glycolate, was higher in patients who subsequently developed kidney failure (P = 0.034). However, the 41% intraindividual variation of urinary oxalate resulted in wide confidence intervals. Conclusion: In conclusion, homozygosity for AGXT null variants and nephrocalcinosis were the strongest determinants for kidney failure in PH1.

Lumasiran in the Management of Patients with Primary Hyperoxaluria Type 1: From Bench to Bedside.

Primary hyperoxaluria (PH) is a rare genetic disease caused by excessive hepatic production and elevated urinary excretion of oxalate that leads to recurrent nephrolithiasis, nephrocalcinosis and, eventually, kidney failure. As glomerular filtration rate declines, oxalate accumulates leading to systemic oxalosis, a debilitating condition with high morbidity and mortality. Although PH is usually diagnosed during infancy, it can present at any age with different phenotypes, ranging from mild symptoms to extremely debilitating manifestations. PH is an autosomal recessive disorder and, to date, three types have been identified: PH1, PH2 and PH3. PH1 is the most common and most aggressive type, accounting for almost 80% of primary hyperoxaluria diagnoses. Until 2020, general treatment for PH1 consisted mainly in high fluid intake, urine alkalization, surgical management of recurrent nephrolithiasis and eventually, if and when kidney failure occurred, intensive dialysis regimens and transplantation strategies (simultaneous or sequential liver-kidney transplant or isolated liver/kidney transplant in carefully selected patients). Specific treatment did and still consists in administration of pyridoxine hydrochloride, although it is only effective in a subset of PH1 patients. Lumasiran, a novel biological drug based on mRNA interference that has been recently approved in the US and European Union, showed promising results and is set to be a turning point in the management of PH1. This literature review aims to summarize the available evidence on PH1 treatment with lumasiran, in order to provide both pediatric and adult nephrologists and clinicians with the knowledge for the identification and management of PH1 patients suitable for treatment.

Why is diagnosis, investigation, and improved management of kidney stone disease important? Non-pharmacological and pharmacological treatments for nephrolithiasis.

INTRODUCTION: Progress in the medical treatment and management of nephrolithiasis has been limited to date and continues to depend on urinary metabolic screening to assess excretion of the main stone constituents, factors determining stone solubility and precipitation, and on dietary and lifestyle recommendations. AREAS COVERED: In this review, we try to highlight some of the broader aspects of kidney stone disease in relation to recent epidemiological and pathophysiological findings, and emerging new treatments. Specifically, this review will cover recent evidence on the association between metabolic risk factors and kidney stone disease, dietary risk factors, and dietary interventions to prevent kidney stones, and how genomics, metabolomics, and proteomics may improve diagnosis and treatment of this troublesome, if rarely fatal, condition. PubMed was used to identify the most suitable references according to our search strategy; only full manuscripts were included. EXPERT OPINION: What is emerging is that kidney stone disease is not an isolated disorder but is systemic in nature with links to important and common comorbidities such as diabetes, hypertension, cardiovascular disease, and chronic kidney disease. These associations support the need to take nephrolithiasis seriously as a medical condition and to adopt a more holistic approach to its investigation and treatment.

Unravelling the Complex Relationship between Diet and Nephrolithiasis: The Role of Nutrigenomics and Nutrigenetics.

Nephrolithiasis is an increasingly prevalent condition, especially in high income countries, and is associated with high morbidity. Extraordinary progress in genetics made the identification of genetic forms of nephrolithiasis possible. These genetic diseases are usually rare and do not account for the most common forms of nephrolithiasis that are the result of several factors such as environment, dietary habits, and predisposing genes. This knowledge has shaped what we classify as nephrolithiasis, a condition that is now recognized as systemic. How and to what extent all these factors interact with one another and end in kidney stone formation, growth, and recurrence is not completely understood. Two new research fields have recently been trying to give some answers: nutrigenomics and nutrigenetics. These fields have the aim of understanding the intricate diet/genome interface that influences gene expression regulation mainly through epigenetic mechanisms and results in specific medical conditions such as cancer, metabolic syndrome, and cardiovascular diseases. Epigenetics seems to play a crucial role and could represent the link between environmental factors, that we are constantly exposed to, and risk factors for nephrolithiasis. In this systematic review, we summarize all the available evidence of proven or hypothesized epigenetic mechanisms related to nephrolithiasis.

Trajectories of Kidney Function in Patients with ATTRv Treated with Gene Silencers.

Hereditary transthyretin amyloidosis (ATTRv; v for "variant") is the most common form of hereditary amyloidosis, with an autosomal dominant inheritance and a variable penetrance. This disease has a significant variability in clinical presentation and multiorgan involvement. While kidney involvement in early-onset ATTRv has been reported in one-third of patients, in late-onset ATTRv it has generally been considered rare. In the present study, we describe trajectories of kidney function over time before and after treatment with gene silencing therapies in a cohort of 17 ATTRv patients with different mutations, coming from Italy (nine subjects treated with inotersen and eight patients treated with patisiran). The analysis of estimated glomerular filtration rate (eGFR) slopes revealed that the average change in eGFR was 0.01 mL/min/1.73 m2 per month before initiation and -0.23 mL/min/1.73 m2 per month during follow-up for inotersen and -0.62 mL/min/1.73 m2 per month before initiation and -0.20 mL/min/1.73 m2 per month during follow-up for patisiran. In conclusion, we did not observe any significant difference either between the two groups of treatment or within-group before and after therapy, so gene-silencing therapies may be considered safe for renal function in ATTRv and are not associated with a worsening of eGFR slope.

Renal Involvement in Hereditary Transthyretin Amyloidosis: An Italian Single-Centre Experience.

OBJECTIVE: Hereditary transthyretin amyloidosis (ATTRv) represents a diagnostic challenge considering the great variability of clinical presentation and multiorgan involvement. In the present study, we report the prevalence of kidney involvement and kidney function over time in a cohort of ATTRv patients with different transthyretin gene mutations. PATIENTS AND METHODS: For this study, we systematically collected data from all patients with a diagnosis of ATTRv followed at the Neurology Unit of Fondazione Policlinico Universitario A. Gemelli IRCCS. Kidney involvement was defined as presence of estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2 obtained with CKD-EPI equation, abnormal urinary protein excretion (UPE) (>150 mg/24 h) and/or albuminuria > 30 mg/24 h (or mg/g creatinine). The analysis included data from 46 patients with 122 measurements of serum creatinine. RESULTS: Among the 46 patients included in the analysis, kidney involvement was present in 37%, with 15% showing reduced eGFR and 22% abnormal UPE (63% of patients with available UPE data). No single predictor was associated with either eGFR values or its slope over time. CONCLUSIONS: Kidney involvement is quite common in patients with ATTRv regardless of the underlying genetic variant. In particular, abnormal UPE appears to be a common feature of the disease.

Management of the kidney transplant patient with Cancer: Report from a Multidisciplinary Consensus Conference.

INTRODUCTION: Cancer is the second most common cause of mortality and morbidity in Kidney Transplant Recipients (KTRs). Immunosuppression can influence the efficacy of cancer treatment and modification of the immunosuppressive regimen may restore anti-neoplastic immune responses improving oncologic prognosis. However, patients and transplant physicians are usually reluctant to modify immunosuppression, fearing rejection and potential graft loss. Due to the lack of extensive and recognised data supporting how to manage the immunosuppressive therapy in KTRs, in the context of immunotherapy, chemotherapy, radiotherapy and loco-regional treatments, a Consensus Conference was organised under the auspices of the European Society of Organ Transplantation and the Italian Society of Organ Transplantation. The conference involved a multidisciplinary group of transplant experts in the field across Europe. METHODS: The overall process included a) the formulation of 12 specific questions based on the PICO methodology, b) systematic literature review and summary for experts for each question, c) a two-day conference celebration and the collection of experts' agreements. The conference was articulated in three sessions: "Immunosuppressive therapy and immunotherapy", "Systemic therapy", "Integrated Therapy", while the final experts' agreement was collected with a televoting procedure and defined according to the majority criterion. RESULTS: Twenty-six European experts attended the conference and expressed their vote. A total of 14 statements were finally elaborated and voted. Strong agreement was found for ten statements, moderate agreement for two, moderate disagreement for one and uncertainty for the last one. CONCLUSIONS: The consensus statements provide guidance to transplant physicians caring for kidney transplant recipients with cancer and indicate key aspects that need to be addressed by future clinical research.

α-lipoic acid in patients with autosomal dominant polycystic kidney disease.

OBJECTIVES: Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney disease characterized by multiple and bilateral cystic dilation of renal tubules. Hypertension, endothelial dysfunction, systemic inflammation, and accelerated atherosclerosis are alterations found at a very early stage of the disease and are responsible for increasing both cardiovascular risks and progression toward end-stage renal disease. The aim of the study was to evaluate the effects of the use of 1.6 g α-lipoic acid (ALA) daily for 3 and 6 on the main markers of systemic inflammation, endothelial dysfunction, and atherosclerosis, as well as on nutritional, cardiovascular, and psychocognitive parameters, in ADPKD patients with CKD stage G2/G3 Kidney Disease Improving Global Outcomes chronic kidney disease (KDIGO) compared to controls. METHODS: This was a controlled, longitudinal, prospective, interventional study with 59 patients with ADPKD. Of the patients, 33 were treated with ALA (1.6 g/d) for 6 mo and 26 were controls. Clinical, laboratory (inflammation and metabolic indexes), instrumental parameters (intima media thickness (IMT), renal resistive index (RRI), flow-mediated dilation (FMD), ankle-brachial index (ABI), and psycho-cognitive tests (Mini-Mental State Examination [MMSE], Hamilton Depression Rating Scale [HAM-D], Beck Depression Inventory-II [BDI-II]) were evaluated at baseline (T0), 3 mo (T1), and 6 mo (T2). RESULTS: Patients treated with ALA at T1 and T2 showed a significant reduction in serum glucose, insulin, homeostatic model assessment-insulin resistance, and serum uric acid (P = 0.013, P = 0.002, P = 0.002, P <0.001; respectively) and significantly higher values of base excess (P < 0.001), compared with the control group. Moreover, the results showed a significant increase in bicarbonates (P = 0.009) and FMD (P < 0.001), and a significant reduction of C-reactive protein (P <0.001) and RRI (P = 0.013). On the other hand, we did not assess a significant difference in IMT and ABI at T1 and T2. Psychocognitive tests (BDI-II, HAM-D, and MMSE) were significantly improved (P = 0.007, P < 0.001, P < 0.001; respectively) in patients treated with ALA for 6 mo compared with the control group. A significant difference in nicotinamide adenine dinucleotide phosphate oxidase 2 concentrations was observed between T0 and T2 only in ADPKD patients treated with ALA (P = 0.039, P = 0.039; respectively), although we did not find a significant difference in interleukin-6, interleukin -1ß, and tumor necrosis factor-α concentrations in either group. CONCLUSIONS: We suggest an early and careful monitoring of traditional and non-traditional cardiovascular risk factors in patients with ADPKD. Moreover, we suggest the use of ALA, an anti-inflammatory and antioxidant nutraceutical with few side effects. Additionally, it is important to evaluate the cognitive abilities, psychological health, and quality of life of patients with ADPKD, especially at the early stage of disease.

[Day of Prevention of Renal Diseases in Amatrice, Italy].

Chronic kidney disease (CKD) is a very common condition and its prevalence is increasing worldwide. The CARHES study in Italy showed a prevalence of 6.5% in women and 7.5% in men. As a matter of fact, an early diagnosis is essential to slow down the progression and improve the renal and cardiovascular prognosis. For this purpose the A.N.Di.P. association (National Association of Peritoneal Dialysis-Onlus "Enzo Siciliano ") organized the DAY OF PREVENTION OF RENAL DISEASES which was held in AMATRICE the 15th of July 2017 called "WE START A NEW PATH OF LIFE TOGETHER". The goal of this initiative was to highlight and spread the importance of prevention and early diagnosis of renal disease in Amatrice and its surroundings. During this day, medical history, blood pressure measurements, urinalysis, serum creatinine and serum uric acid were carried out and we suggested to patients how to proceed, if necessary, in a further diagnostic and therapeutic process. We also recommended a correct lifestyle, based on healthy eating and regular physical activity. The choice to dedicate particular attention to the population tragically affected by the earthquake occurred to identify renal diseases, since they are a possible consequence of the earthquake, to draw attention to the importance of renal function and to demonstrate that simple routine checks may lead to an early diagnosis of unrecognized kidney diseases, also reducing cardiovascular risk.