Genetic Diagnosis of Adult Hemodialysis Patients With Unknown Etiology.

Introduction: Kidney disease of unknown etiology accounts for 1 in 10 adult end-stage renal disease (ESRD) cases worldwide. The aim of this study is to clarify the genetic background of patients with chronic kidney disease (CKD) of unknown etiology who initiated renal replacement therapy (RRT) in adulthood. Methods: This is a multicenter cross-sectional cohort study. Of the 1164 patients who attended 4 dialysis clinics in Japan, we first selected patients who started RRT between the ages of 20 and 49 years. After excluding patients with apparent causes of CKD (e.g., diabetic nephropathy, polycystic kidney disease (PKD) with family history, patients who underwent renal biopsy), 90 patients with CKD of unknown cause were included. The 298 genes associated with CKD were analyzed using capture-based targeted next-generation sequencing. Results: Of the 90 patients, 10 (11.1%) had pathogenic variants in CKD-causing genes and 17 (18.9%) had variant of unknown significance (VUS). Three patients had PKD1 pathogenic variants, and 1 patient had PKD1 and COL4A4 pathogenic variants. In addition, 2 patients were diagnosed with atypical hemolytic uremic syndrome (aHUS) due to C3 or CFHR5. One patient each was diagnosed with Alport syndrome due to COL4A4 and COL4A3 variants, nephronophthisis due to NPHP1 variants, Fabry disease due to GLA variants, and autosomal-dominant tubulointerstitial kidney disease due to UMOD variants. Genetic diagnoses were not concordant with clinical diagnoses, except for patients with PKD1 variant. Conclusion: This largest study on genetic analysis in hemodialysis-dependent adults revealed the presence of undiagnosed inherited kidney diseases.

CFAP47 is a novel causative gene implicated in X-linked polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a well-described condition in which ~80% of cases have a genetic explanation, while the genetic basis of sporadic cystic kidney disease in adults remains unclear in ~30% of cases. This study aimed to identify novel genes associated with polycystic kidney disease (PKD) in patients with sporadic cystic kidney disease in which a clear genetic change was not identified in established genes. A next-generation sequencing panel analyzed known genes related to renal cysts in 118 sporadic cases, followed by whole-genome sequencing on 47 unrelated individuals without identified candidate variants. Three male patients were found to have rare missense variants in the X-linked gene Cilia And Flagella Associated Protein 47 (CFAP47). CFAP47 was expressed in primary cilia of human renal tubules, and knockout mice exhibited vacuolation of tubular cells and tubular dilation, providing evidence that CFAP47 is a causative gene involved in cyst formation. This discovery of CFAP47 as a newly identified gene associated with PKD, displaying X-linked inheritance, emphasizes the need for further cases to understand the role of CFAP47 in PKD.

Changes in Metabolomic Profiles Induced by Switching from an Erythropoiesis-Stimulating Agent to a Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitor in Hemodialysis Patients: A Pilot Study.

Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are a new class of medications for managing renal anemia in patients with chronic kidney disease (CKD). In addition to their erythropoietic activity, HIF-PHIs exhibit multifaceted effects on iron and glucose metabolism, mitochondrial metabolism, and angiogenesis through the regulation of a wide range of HIF-responsive gene expressions. However, the systemic biological effects of HIF-PHIs in CKD patients have not been fully explored. In this prospective, single-center study, we comprehensively investigated changes in plasma metabolomic profiles following the switch from an erythropoiesis-stimulating agent (ESA) to an HIF-PHI, daprodustat, in 10 maintenance hemodialysis patients. Plasma metabolites were measured before and three months after the switch from an ESA to an HIF-PHI. Among 106 individual markers detected in plasma, significant changes were found in four compounds (erythrulose, n-butyrylglycine, threonine, and leucine), and notable but non-significant changes were found in another five compounds (inositol, phosphoric acid, lyxose, arabinose, and hydroxylamine). Pathway analysis indicated decreased levels of plasma metabolites, particularly those involved in phosphatidylinositol signaling, ascorbate and aldarate metabolism, and inositol phosphate metabolism. Our results provide detailed insights into the systemic biological effects of HIF-PHIs in hemodialysis patients and are expected to contribute to an evaluation of the potential side effects that may result from long-term use of this class of drugs.

Chapter 1: Evaluation of kidney function in patients undergoing anticancer drug therapy, from clinical practice guidelines for the management of kidney injury during anticancer drug therapy 2022.

The prevalence of CKD may be higher in patients with cancer than in those without due to the addition of cancer-specific risk factors to those already present for CKD. In this review, we describe the evaluation of kidney function in patients undergoing anticancer drug therapy. When anticancer drug therapy is administered, kidney function is evaluated to (1) set the dose of renally excretable drugs, (2) detect kidney disease associated with the cancer and its treatment, and (3) obtain baseline values for long-term monitoring. Owing to some requirements for use in clinical practice, a GFR estimation method such as the Cockcroft-Gault, MDRD, CKD-EPI, and the Japanese Society of Nephrology's GFR estimation formula has been developed that is simple, inexpensive, and provides rapid results. However, an important clinical question is whether they can be used as a method of GFR evaluation in patients with cancer. When designing a drug dosing regimen in consideration of kidney function, it is important to make a comprehensive judgment, recognizing that there are limitations regardless of which estimation formula is used or if GFR is directly measured. Although CTCAEs are commonly used as criteria for evaluating kidney disease-related adverse events that occur during anticancer drug therapy, a specialized approach using KDIGO criteria or other criteria is required when nephrologists intervene in treatment. Each drug is associated with the different disorders related to the kidney. And various risk factors for kidney disease associated with each anticancer drug therapy.

Different Clinical Courses of Nephronophthisis in Dizygotic Twins.

Siblings with nephronophthisis occasionally show different clinical courses; however, the reasons for this remain unclear. We herein report cases of nephronophthisis in a pair of dizygotic twins with different clinical courses. The brother developed end-stage kidney disease at 17 years old; however, his sister did not show kidney insufficiency. Kidney biopsies revealed severe tubulointerstitial damage at 14 and 22 years old in the brother and sister, respectively. Both had a homozygous NPHP1 deletion with different heterozygous mutations related to hereditary cystic kidney disease. Since the dizygotic twins were exposed to similar environmental factors, genetic factors may have influenced their clinical course more strongly than environmental factors.

Echocardiographic Findings and Genotypes in Autosomal Dominant Polycystic Kidney Disease.

Background: Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary cystic kidney disease and is well known to have extrarenal complications. Cardiovascular complications are of particular clinical relevance because of their morbidity and mortality; however, unclear is why they occur so frequently in patients with ADPKD and whether they are related to the genotypes. Methods: We extracted and retrospectively analyzed clinical data on patients with ADPKD who underwent echocardiography and whose genotype was confirmed by genetic testing between April 2016 and December 2020. We used next-generation sequencing to compare cardiac function, structural data, and the presence of cardiac valvular disease in patients with 1 of 3 genotypes: PKD1, PKD2, and non-PKD1, 2. Results: This retrospective study included 65 patients with ADPKD. Patients were divided into 3 groups: PKD1, n = 32; PKD2, n = 12; and non-PKD1, 2, n = 21. The prevalence of mitral regurgitation (MR) was significantly higher in the PKD1 group than in the PKD2 and non-PKD1, 2 group (46.9% vs. 8.3% vs. 19.0%, respectively; p = 0.02). In contrast, no significant difference was found for other cardiac valve complications. Conclusion: This study found a significantly higher prevalence of MR in patients with the PKD1 genotype than in those with the PKD2 or non-PKD1, 2 genotypes. Physicians may need to perform echocardiography earlier and more frequently in patients with ADPKD and the PKD1 genotype and to control fluid volume and blood pressure more strictly in these patients to prevent future cardiac events.

A case of systemic sarcoidosis with mesangial proliferative glomerulonephritis showing predominant deposition of IgG in the mesangial region.

A 37-year-old African-British man was referred to our hospital for detailed examination because of persistent fever, swelling and pain in both ankle joints, and blurred vision for two months. Inguinal lymph node biopsy showed a large number of epithelioid granulomas without necrosis. Granulomatous anterior uveitis, nephropathy, high serum angiotensin-converting enzyme activity, and high serum-soluble interleukin-2 receptor were observed, and the diagnosis of systemic sarcoidosis was made. His serum creatinine was 1.4 mg/dL and hematuria, leukocyturia, and urine protein were also seen. The renal biopsy finding was mesangial proliferative glomerulonephritis, with no findings of granuloma formation or tubular interstitial nephritis. Immunofluorescence staining showed deposition of IgG, C3, and C1q in the mesangial region. IgG3 was dominant in subclass staining. There was no monoclonality on kappa and lambda staining. Electron microscopy showed predominant deposition in the mesangial region with some subepithelial and endothelial deposition. His hematuria and leukocyturia disappeared with steroid therapy, suggesting sarcoidosis-related nephropathy. A case of systemic sarcoidosis with mesangial proliferative glomerulonephritis showing predominant deposition of IgG in the mesangial region is presented. No cases of such histological findings have been reported so far, and it is necessary to analyze further cases to clarify the pathogenic significance of the renal biopsy findings observed in this case.

A Novel LMX1B Variant Identified in a Patient Presenting with Severe Renal Involvement and Thin Glomerular Basement Membrane.

We report a case of nail-patella syndrome (NPS) with unusual thinning of the glomerular basement membrane (GBM) associated with a novel heterozygous variant in the LMX1B gene. A 43-year-old female patient with a previous diagnosis of NPS, referred to our hospital for persistent proteinuria, underwent a renal biopsy, which revealed minor glomerular abnormalities. She underwent a second renal biopsy at the age of 56 owing to the presence of persistent proteinuria and decline in serum albumin, meeting the diagnostic criteria for nephrotic syndrome. Light microscopy demonstrated glomerulosclerosis and cystic dilatation of the renal tubules. Notably, electron microscopy revealed unusual thinning of the GBM, which is quite different from typical biopsy findings observed in patients with NPS, characterized by thick GBM with fibrillary material and electron-lucent structures. Comprehensive genetic screening for 168 known genes responsible for inherited kidney diseases using a next-generation sequencing panel identified a novel heterozygous in-frame deletion-insertion (c.723_729delinsCAAC: p.[Ser242_Lys243delinsAsn]) in exon 4 of the LMX1B gene, which may account for the disrupted GBM structure. Further studies are warranted to elucidate the complex genotype-phenotype relationship between LMX1B and proper GBM morphogenesis.

Genetic Background and Clinicopathologic Features of Adult-onset Nephronophthisis.

INTRODUCTION: Recently, nephronophthisis (NPH) has been considered a monogenic cause of end-stage renal disease (ESRD) in adults. However, adult-onset NPH is difficult to accurately diagnose and has not been reported in a cohort study. In this study, we assessed the genetic background and clinicopathologic features of adult NPH. METHODS: We investigated 18 sporadic adult patients who were suspected as having NPH by renal biopsy. We analyzed 69 genes that cause hereditary cystic kidney disease and compared clinicopathologic findings between patients with and without pathogenic mutations in NPH-causing genes. RESULTS: Seven of 18 patients had pathogenic NPH-causing mutations in NPHP1, NPHP3, NPHP4, or CEP164. Compared with patients without pathogenic mutations, those with pathogenic mutations were significantly younger but did not significantly differ in the classic NPH pathologic findings, such as tubular cysts. On the other hand, the number of tubules with thick tubular basement membrane (TBM) duplication, which was defined as >10-µm thickness, was significantly higher in patients with genetically proven adult NPH than in those without pathogenic mutations. α-Smooth muscle actin (α-SMA)-positive myofibroblasts were detected inside thick TBM duplication. CONCLUSIONS: In adult patients with NPH, thick TBM duplication was the specific finding. Our analysis also suggested that older patients tended to have no pathogenic mutations, even when they were suspected to have NPH by renal biopsy. These findings could be the novel clinical clue for the diagnosis of NPH in adult patients.

Association between chronic kidney disease and mortality in stage IV cancer.

BACKGROUND: Chronic kidney disease (CKD) is known to be associated with cancer mortality. However, no study has considered the well-known cancer prognostic factors, ECOG Performance Status (PS) and cancer treatment, as confounding factors. We assessed the independent relationship between CKD and cancer death in stage IV cancer patients. METHODS: In this retrospective observational study, we included stage IV cancer patients diagnosed from 2009 to 2014 in a single center. We collected baseline clinical and laboratory variables, and cancer-specific variables, and assessed the presence of CKD. Our primary outcome was all-cause mortality. The secondary outcome was cancer-specific mortality and site-specific cancer mortality. RESULTS: Among 961 eligible stage IV cancer patients (median age 69 years, 51.8% male), 150 patients had CKD. During follow-up (median 9.8 months), 638 patients died, of whom 526 patients died from cancer. After adjusting for prognostic variables, including ECOG PS and cancer treatment, all-cause mortality and cancer-specific mortality were significantly higher in CKD patients than in non-CKD patients (HR 1.41, 95% CI 1.13-1.77 and HR 1.43, 95% CI 1.12-1.83, respectively). In patients with breast and kidney and urinary tract cancers, CKD was associated with a significantly increased risk of death (HR 7.01, 95% CI 1.47-33.4 and HR 3.33, 95% CI 1.42-7.78, respectively). CONCLUSIONS: CKD at the time of stage IV cancer diagnosis was associated with all-cause mortality and cancer-specific mortality. Moreover, the association between CKD and cancer-specific death was site specific for breast cancer and kidney and urinary tract cancer.

Renal TNFα activates the WNK phosphorylation cascade and contributes to salt-sensitive hypertension in chronic kidney disease.

The inappropriate over-activation of the with-no-lysine kinase (WNK)-STE20/SPS1-related proline/alanine-rich kinase (SPAK)-sodium chloride cotransporter (NCC) phosphorylation cascade increases sodium reabsorption in distal kidney nephrons, resulting in salt-sensitive hypertension. Although chronic kidney disease (CKD) is a common cause of salt-sensitive hypertension, the involvement of the WNK phosphorylation cascade is unknown. Moreover, the effect of immune systems on WNK kinases has not been investigated despite the fact that immune systems are important for salt sensitivity. Here we demonstrate that the protein abundance of WNK1, but not of WNK4, was increased at the distal convoluted tubules in the aristolochic acid nephropathy mouse model of CKD. Accordingly, the phosphorylation of both SPAK and NCC was also increased. Moreover, a high-salt diet did not adequately suppress activation of the WNK1-SPAK-NCC phosphorylation cascade in this model, leading to salt-sensitive hypertension. WNK1 also was increased in adenine nephropathy, but not in subtotal nephrectomy, models of CKD. By comparing the transcripts of these three models focusing on immune systems, we hypothesized that tumor necrosis factor (TNF)-α regulates WNK1 protein expression. In fact, TNF-α increased WNK1 protein expression in cultured renal tubular cells by reducing the transcription and protein levels of NEDD4-2 E3-ligase, which degrades WNK1 protein. Furthermore, the TNF-α inhibitor etanercept reversed the reduction of NEDD4-2 expression and upregulation of the WNK1-SPAK-NCC phosphorylation cascade in distal convoluted tubules in vivo in the aristolochic acid nephropathy model. Thus, salt-sensitive hypertension is induced in CKD via activation of the renal WNK1- SPAK-NCC phosphorylation cascade by TNF-α, reflecting a link with the immune system.

Serial measurement of electrolyte and citrate concentrations in blood-primed continuous hemodialysis circuits during closed-circuit dialysis.

BACKGROUND: For continuous renal replacement therapy in small infants, due to the large extracorporeal volume involved, blood priming can be necessary to prevent hypotension and hemodilution. Because packed red blood cells (RBCs) have high levels of potassium and citrate, closed-circuit dialysis is often performed. We assessed the metrics of closed-circuit dialysis and serial citrate concentration changes. METHODS: We performed dialysis of closed circuits primed with expired human packed RBC solution and 5% albumin. Blood and dialysate flow rates were 70 and 33.3 mL/min, respectively. The extracorporeal volume was 70 mL. We measured pH, electrolytes, and citrate in the closed circuit every 3 min for 15 min. We also assessed the adequacy of closed-circuit dialysis using the formula: [dialysate flow rate (mL/min) × time of dialysis (min)]/extracorporeal volume (mL) and we assessed the correlation between citrate and ionized calcium concentrations. RESULTS: To reach normal concentrations of sodium, potassium, and chloride, 2.4 times as much dialysate fluid as extracorporeal volume was needed. In contrast, for ionized calcium, bicarbonate, and citrate, 3.8 times as much dialysate fluid as extracorporeal volume was required. By simple linear regression analysis, the concentration of citrate was significantly correlated with that of ionized calcium. CONCLUSIONS: For closed-circuit dialysis using an RBC solution, the formula [dialysate flow rate (mL/min) × time of dialysis (min)]/extracorporeal volume (mL) would be a better parameter to estimate efficacy, compared with other metrics. Additionally, the citrate concentration can be readily estimated from the ionized calcium concentration during closed-circuit dialysis.

Everolimus Reduces the Size of Tuberous Sclerosis Complex-Related Huge Renal Angiomyolipomas Exceeding 20 cm in the Longest Diameter.

We evaluated the efficacy of everolimus in 3 patients who had huge renal angiomyolipomas associated with tuberous sclerosis complex. Two patients with large lipid-rich angiomyolipomas had a history of renal transarterial embolization for renal bleeding, but the effect had only been temporary and the embolized kidneys had continued to enlarge. In case 1, case 2, and case 3, total renal volume was respectively 3,891, 4,035, and 1,179 cm3 before administration of everolimus, decreasing to 3,016 (77%), 3,043 (75%), and 1,051 (89%) cm3 after 1 year of everolimus therapy and to 2,832 (73%), 3,209 (80%), and 1,102 (93%) cm3 after 3 years. New renal bleeding did not occur, but elevation of serum creatinine and urinary protein were noted in 2 patients. While previous reports have largely assessed the effect of everolimus for angiomyolipomas of < 10 cm in the longest diameter, our findings suggest that this drug might also be effective for huge lesions of > 20 cm in diameter. However, total renal volume still exceeds 2,000 cm3 in 2 of our patients, suggesting limited size reduction of lipid-rich angiomyolipomas. In addition, occurrence of everolimus-related nephropathy needs to be monitored carefully.

Transcatheter Arterial Embolization Therapy for Huge Renal Cysts: Two Case Reports.

We encountered 2 patients with symptomatic huge simple renal cysts. In case 1, 4,000 mL of cyst fluid was drained via a catheter, but intracystic bleeding occurred immediately afterwards. Transcatheter arterial embolization (TAE) was performed, after which the bleeding stopped, and cyst drainage was repeated successfully. After 2 years, the total cyst volume was reduced from 11,775 mL to 75.4 mL. In case 2, TAE was performed prophylactically before drainage. Subsequently, 9,400 mL of fluid was removed from multiple cysts. After 1 year, the total cyst volume was reduced from 9,215 mL to 633 mL without bleeding. Based on these 2 cases, prophylactic TAE before drainage may be useful in patients with huge renal cysts.

[Transplantation-associated thrombotic microangiopathy confirmed by renal biopsy].

An eight-year-old girl with myelodysplastic syndrome (refractory cytopenia) received a bone marrow transplant (BMT) from an unrelated donor because of immunosuppressive therapy failure. Following administration of foscarnet for cytomegalovirus reactivation at day40 post-BMT, serum creatinine increased, and proteinuria, hematuria, and hypertension gradually exacerbated and became prolonged. However, neither schistocytosis nor other organ damage was evident. At six months post-BMT, renal biopsy revealed diffuse glomerular damage with glomerular lobulation, a double contour of the glomerular basement membrane, erythrocyte congestion and thrombi in the glomerular endocapillaries, and mesangiolysis, confirming the diagnosis of transplantation-associated thrombotic microangiopathy (TA-TMA). We initiated strict controls regarding fluid balance, salt intake, and blood pressure. The patient's renal function improved 10 months post-BMT. TA-TMA often presents as non-specific symptoms, making diagnosis difficult. In cases of post-transplant renal damage, TA-TMA should be differentiated regardless of whether specific symptoms such as hemolytic anemia and other organ failure are evident, and a renal biopsy should, therefore, be considered.

Decreased levels of inflammatory cytokines in immunoglobulin-resistant Kawasaki disease after plasma exchange.

The pathogenesis of coronary artery aneurysm (CAA) formation in Kawasaki disease (KD) remains unknown. However, inflammatory cytokines are thought to play an important role in KD. Patients with intravenous immunoglobulin (IVIG)-resistant KD are more likely to develop CAA. For such refractory patients, steroids and emerging infliximab (IFX) are used; however, further verification is required for their efficacy and safety. Plasma exchange (PE), which removes various inflammatory cytokines, has been used in Japan for over 15 years to prevent CAA in IVIG-resistant KD patients. The sequential change in inflammatory cytokines during the time course of PE has yet to be investigated. In this study, we measured plasma levels of 13 cytokines in nine children with IVIG-resistant KD before the start of PE (day 0: D0), as well as at 1 or 2 days (D1/2), and 4 or 5 days (D4/5) after starting PE. The median age of onset was 8 months (range: 3-53 months). Before PE, patients were treated with IVIG (median dose: 4 g/kg, range: 3-4 g/kg). The median starting period of PE was 8 days after the onset of fever (range: 6-21 days), while its duration was 3 days (range: 2-5 days). Among the 13 cytokines, interleukin-6, tumor necrosis factor-α, tumor necrosis factor receptor I (TNFR1), TNFR2, granulocyte colony-stimulating factor, and IL-17 were significantly lower at D4/5 compared with D0 and/or D1/2, reflecting the potential central efficacy of PE. While three patients developed moderate CAA, their condition regressed within 1 year. The removal of inflammatory cytokines could be the central efficacy of PE against refractory KD.

Successful remission induced by plasma exchange combined with leukocytapheresis against refractory systemic juvenile idiopathic arthritis.

Systemic juvenile idiopathic arthritis (sJIA) is an inflammatory cytokine-related disorder associated with overproduction of interleukin (IL)-6, IL-1ß, and IL-18. Macrophage activation syndrome (MAS) is a critical and lethal complication of sJIA. Therefore, prompt induction of remission in the active phase of sJIA is important for prevention of MAS. However, treatment of corticosteroid-resistant sJIA is still challenging. We propose a new strategy to induce remission in the active phase of sJIA. A 7-year-old boy with new-onset sJIA was treated with oral prednisolone, methylprednisolone pulse therapy, and parenteral cyclosporine, but he continuously showed remittent high fever, arthralgia, skin rash, and elevation of inflammatory markers, including hyperferritinemia. Because of impending MAS, plasma exchange was started, but he was resistant to plasma exchange. Therefore, we combined leukocytapheresis with PE. After five PE and two leukocytapheresis sessions, he finally achieved remission in accordance with a reduction in inflammatory cytokines. Elevated serum tumor necrosis factor-α, interferon-γ, and IL-12 levels returned to normal 10 days after initiating plasma exchange combined with leukocytapheresis, with a reduction in white blood cell count. In conclusion, plasma exchange combined with leukocytapheresis is a new alternative option to induce remission for patients with methylprednisolone pulse therapy- or cyclosporine-refractory sJIA.