An IgA1-lambda-type monoclonal immunoglobulin deposition disease associated with membranous features in a patient with IgG4-related kidney disease: a case report.

BACKGROUND: IgG4-related disease (IgG4-RD) is a newly recognized fibroinflammatory condition. The kidney is one of the organs commonly affected by IgG4-RD. Tubulointerstitial nephritis (TIN) is the main feature, and membranous nephropathy (MN) has also been described frequently. In MN, polyclonal immunoglobulins and complements are deposited in granular form along the glomerular basement membranes (GBMs). Unusual cases of monoclonal immunoglobulin deposition disease (MIDD) associated with membranous features have been reported. MIDD is morphologically similar to MN but contains immunoglobulins considered to be derived from single B-cell clone. CASE PRESENTATION: We describe a 65-year-old man who was referred to our hospital because of hyperproteinaemia, eosinophilia, anaemia, and proteinuria. A renal biopsy demonstrated infiltration of plasma cells and eosinophils in the interstitium, and the ratio of IgG4-positive plasma cells to IgG-positive plasma cells was 55%. The patient was diagnosed as having IgG4-related TIN. Periodic acid methenamine silver staining under light microscopy revealed a bubbling appearance and spike formation in the GBM. On immunofluorescence, the expression of IgG and complements was negative; however, IgA was positively expressed in a granular pattern along the GBM. An IgA subclass analysis revealed a significant deposition of IgA1-lambda (IgA1-λ). Electron microscopy revealed irregular and small non-organized and non-Randall-type granular electron-dense deposits in the GBM that were shaped like snow leopard spots. CONCLUSIONS: After corticosteroid therapy was initiated, the patient's eosinophilia remarkably improved and his serum creatinine, IgG, and IgG4 levels decreased to within the normal ranges. However, massive proteinuria persisted. To our knowledge, this is the first reported case of IgG4-related TIN associated with IgA1-λ-type MIDD with membranous features.

Intact parathyroid hormone and whole parathyroid hormone assay results disagree in hemodialysis patients under cinacalcet hydrochloride therapy.

BACKGROUND: The parathyroid gland secretes 1-84 and 7-84 parathyroid hormone (PTH) fragments, and its regulation is dependent on stimulation of the extracellular calcium-sensing receptor. While the intact PTH system detects both PTH fragments, the whole PTH system detects the 1-84PTH but not the 7-84PTH. Cinacalcet hydrochloride (CH) binds to calcium-sensing receptor as a calcimimetic. Here we investigated the role of CH treatment in the assessment of parathyroid gland function. METHODS: Stable adult dialysis patients for whom CH therapy was planned were included. Patients for whom CH therapy was not planned were simultaneously included as the control group. RESULTS: The CH group (n = 44) showed significantly higher circulating levels of Ca, intact PTH, and whole PTH, before the CH treatment than the control group (n = 112). The Ca, intact PTH, and whole PTH levels decreased along with the CH therapy, and the Ca levels became comparable in the 8th week of treatment and thereafter. The CH group in the 8th week and thereafter showed significantly lower whole/intact PTH ratios than the control group, while the whole/intact PTH ratio was not significantly different between before and during the CH therapy. A multiple regression analysis revealed that the whole/intact PTH ratio was almost constant, but both the serum Ca level and a CH therapy could potentially modify the fixed number. When the whole PTH levels were estimated by intact PTH levels using the relationship between them in the control group, the levels were clearly overestimated in the CH group. CONCLUSIONS: Although the direct effect of CH on the whole/intact PTH ratio is masked by its hypocalcemic action, we could successfully demonstrate that the ratio in CH users is lower than that in the non-users with comparable levels of serum Ca. Evaluating parathyroid function with intact PTH according to the clinical practice guidelines in patients being treated with CH may lead to significant overestimation and subsequent overtreatment.

[A case of PR3-ANCA positive granulomatosis with polyangiitis recurrent with acute kidney injury after 7 years remission].

A 62-year-old-Japanese man had a history of probable granulomatosis with polyangiitis (GPA) from 7 years previously, showing kidney and vasculitis symptoms with PR3-ANCA (864 EU) without renal biopsy. Remission with normalization of renal function and urinary findings was induced by corticosteroid therapy. Prednisolone (PSL) was tapered to 5 mg/day and maintained for 6.5 years with a low positive titer of PR3-ANCA. After 7 years of remission, he was referred to our hospital because of arthralgia, fever, general fatigue and appetite loss with apparent urinary abnormality, increased serum Cr (1.8 mg/dL) and C reactive protein (CRP : 30.1 mg/dL). On admission, he showed a high titer of PR3-ANCA (> 300 U/mL). Renal biopsy demonstrated the existence of the pauci-immune type of severe crescentic necrotizing glomerulonephritis, tubulo-interstitial damage and perivascular granuloma. He was diagnosed as relapse of GPA (kidney-localized type) without upper respiratory tract (E) and lung (L) symptoms. Accordingly, he received steroid pulse therapy leading to improvement of these symptoms and renal function. Oral PSL at the dosage of 40 mg/day was administered after steroid pulse therapy, and then tapered to 20 mg/day. Cyclophosphamide was added within 8 weeks. He was discharged 8 weeks after treatment with a decreased level of Cr (1.5 mg/dL) and PR3-ANCA (244 U/mL). After discharge, PSL was tapered to 10 mg/day during the course of stability resulting in a further improved level of Cr (1.2 mg/dL), PR3-ANCA 40 U/mL in the outpatient clinic. In Japan, PR3-ANCA-positive GPA has a lower incidence than MPO-ANCA-positive microscopic vasculitis. In GPA, the kidney-localized (K) type without upper respiratory tract (E, L) symptoms is rare. Histologically, not only necrotizing crescentic glomerulonephritis but also perivascular granuloma in the kidney are very rare and interesting.

Japan Renal Biopsy Registry and Japan Kidney Disease Registry: Committee Report for 2009 and 2010.

The Japan Renal Biopsy Registry (J-RBR) was started in 2007 and the Japan Kidney Disease Registry (J-KDR) was then started in 2009 by the Committee for Standardization of Renal Pathological Diagnosis and the Committee for the Kidney Disease Registry of the Japanese Society of Nephrology. The purpose of this report is to describe and summarize the registered data from 2009 and 2010. For the J-KDR, data were collected from 4,016 cases, including 3,336 (83.1 %) by the J-RBR and 680 (16.9 %) other cases from 59 centers in 2009, and from 4,681 cases including 4,106 J-RBR cases (87.7 %) and 575 other cases (12.3 %) from 94 centers in 2010, including the affiliate hospitals. In the J-RBR, 3,165 native kidneys (94.9 %) and 171 renal grafts (5.1 %) and 3,869 native kidneys (94.2 %) and 237 renal grafts (5.8 %) were registered in 2009 and 2010, respectively. Patients younger than 20 years of age comprised 12.1 % of the registered cases, and those 65 years and over comprised 24.5 % of the cases with native kidneys in 2009 and 2010. The most common clinical diagnosis was chronic nephritic syndrome (55.4 % and 50.0 % in 2009 and 2010, respectively), followed by nephrotic syndrome (22.4 % and 27.0 %); the most frequent pathological diagnosis as classified by the pathogenesis was IgA nephropathy (31.6 % and 30.4 %), followed by primary glomerular diseases (except IgA nephropathy) (27.2 % and 28.1 %). Among the primary glomerular diseases (except IgA nephropathy) in the patients with nephrotic syndrome, membranous nephropathy was the most common histopathology in 2009 (40.3 %) and minor glomerular abnormalities (50.0 %) were the most common in 2010 in native kidneys in the J-RBR. Five new secondary and longitudinal research studies by the J-KDR were started in 2009 and one was started in 2010.

A Case Report of Successful Renal Transplantation After Surgically Treated Type A Aortic Dissection.

BACKGROUND: Aortoiliac lesions can influence the results of kidney transplantation and increase technical difficulties during surgery. Aortic dissection (AD) is a rare and infrequently reported event before transplantation, whereas immediate optimal perfusion is paramount for kidney transplantation. Thus, adequate blood flow imposed by the flow from the true lumen must be considered when choosing a target inflow vessel. CASE PRESENTATION: A 67-year-old man on dialysis with end-stage renal disease caused by immunoglobulin A nephropathy was referred for kidney transplantation. He had successfully undergone conventional Stanford type A AD surgery 3 years ago. Pretransplant contrast-enhanced computed tomography angiography revealed termination of the distal intimal flaps within the common iliac arteries. Dilation of the descending aorta was also observed. Based on the meticulous vascular assessment, including consultation with the cardiovascular surgery department, the right internal iliac artery (IIA) was considered usable for anastomosis. He underwent living unrelated kidney transplantation from his 66-year-old wife. The patency and blood flow in the right IIA were also verified using intraoperative findings. Without any special procedure, we used a side-to-end arterial anastomosis between the donor renal artery and recipient IIA. After vascular clamp removal, the allograft was perfused homogeneously and immediately functioned. CONCLUSION: Patients receiving previous surgery for type A AD can successfully undergo kidney transplantation if the patency of the iliac arteries from the true lumen is confirmed by perioperative evaluation, and the artery can be carefully clamped to avoid possible further dissection.

A Case Report of Successful Kidney Transplantation in a Patient With Autosomal Dominant Polycystic Kidney Disease Who Underwent Thoracic Endovascular Aortic Repair for Type B Aortic Dissection.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is associated with several cardiovascular disorders, including aortic dissection, which preferentially occurs at the thoracic or abdominal level. Because there are few case reports describing surgical repair for aortic dissection followed by renal transplantation in patients with ADPKD, kidney transplantation performed after repair for aortic dissection remains challenging. CASE PRESENTATION: A 34-year-old Japanese man with end-stage renal disease secondary to ADPKD underwent thoracic endovascular aortic repair for complicated acute type B aortic dissection 12 months earlier. A contrast computed tomography scan before transplantation revealed an aortic dissection involving the descending aorta proximal to the common iliac arteries and confirmed multiple large bilateral renal cysts. After simultaneous right native nephrectomy, the patient underwent preemptive living-donor kidney transplantation obtained from his mother. Intraoperatively, we noted that dissection of the external iliac vessels was difficult because of dense adhesions. Arterial clamping was performed immediately below the bifurcation of the internal iliac artery to prevent further aortic dissection of the external iliac artery. After end-to-end anastomosis to the internal iliac artery was completed and the vascular clamp was released, the kidney began to produce urine immediately. CONCLUSION: This case suggests that kidney transplantation in patients undergoing endovascular aortic repair for aortic dissection can be performed by adequately applying a vascular clamp proximal to the internal iliac artery during vascular anastomosis.

Anti-MDA5 Antibody-positive Dermatomyositis with Rapidly Progressive Interstitial Pneumonia Presenting with Nephrotic Syndrome during Treatment with Corticosteroids and Cyclosporine.

A 50-year-old Japanese woman with anti-melanoma differentiation-associated gene 5 antibody (anti-MDA5 antibody)-positive dermatomyositis presenting with rapidly progressive interstitial pneumonia was treated with corticosteroids and cyclosporine. She developed nephrotic syndrome during the treatment regimen with corticosteroids and cyclosporine. A kidney biopsy revealed a thrombotic microangiopathy (TMA) glomerular lesion. Anti-MDA5 antibody-positive dermatomyositis is prone to severe interstitial lung disease (ILD) and is often exacerbated and refractory to treatment. Renal symptoms might be due to TMA of the kidney, and this may be a sign that more intensive treatment is needed. Patients sometimes develop acute kidney injury, which may be due to the TMA.

Social independence evaluation index for Japanese patients with childhood-onset chronic diseases.

Introduction: This study established an independent evaluation index for patients with childhood-onset chronic diseases in Japan. Methods: From November to December 2020, three Delphi rounds were conducted. Thirty-nine participants completed at least one survey. We asked them about targets of social independence for 10 types of activities (education/labor/finance/acquisition of necessities/housing/transportation/leisure/social relationship/intimate relationships/sexuality). The Delphi technique was to be repeated until a consensus of over 80% of participants was reached. Results: The targets chosen for measuring independence in patients with childhood-onset chronic diseases were as follows: "Graduation from high school," "Labor for livelihood (including temporary turnover)," "Financially independent (including temporary turnover, excluding students)," "Buy or rent a house and buy the daily necessities and get the public services you need to live," "Do housework alone," "Plan alone and use transportation to get around," "Participate in play/recreation/leisure activities on own initiative," "Engage in relationships with other people outside of a limited environment (home, school, office, hospital, etc.)," "Create and maintain intimate or romantic relationships between individuals (couples, lovers, sexual partners)," and "Use or know how to use contraceptives and how to prevent sexually transmitted diseases." Conclusions: We established an independent evaluation index for patients with childhood-onset chronic diseases in Japan through a three-round Delphi process. The assessment of social independence using our independent evaluation index may help plan for and provide appropriate support and assistance to these patients.

Role of Early Serial Renal Transplant Allograft Protocol Biopsies in Living Kidney Transplantations.

PURPOSE: This study aimed to analyze the incidence of subclinical rejection (SCR) in kidney transplantation patients and risk factors associated with SCR. METHODS: We assessed 80 protocol biopsies taken within 2 years postoperatively in 41 adult patients who underwent living donor kidney transplantation between 2017 and 2020. All patients were on immunosuppressant therapy that included tacrolimus, mycophenolate mofetil, and steroids. RESULTS: The prevalence of Banff Borderline classification at 3, 6, and 12 months after transplantation was 4%, 5%, and 8 %, respectively, whereas none of the biopsies met the Banff criteria for acute T cell-mediated rejection throughout the study period. Active antibody-mediated rejection (ABMR) was only present in 8% of patients at 3 months after transplantation and chronic active ABMR at 6, 12, and 24 months after transplantation was detected in 10%, 13%, and 11% of the patients, respectively. Subgroup analysis revealed that 50% of the 6 patients with preformed anti-donor specific antibodies (DSAs) developed clinical or subclinical active ABMR within 3 months after transplantation, followed by chronic active ABMR according to serial histologic assessment. Conversely, only a small proportion of patients (3%) without preformed DSAs exhibited clinically active ABMR. CONCLUSIONS: SCR occurs too infrequently in patients with low immunologic risk and strong contemporary immunosuppression therapy to justify the diagnostic effort of serial protocol biopsies. However, protocol biopsies remain an indispensable tool in renal transplant monitoring and may be especially important in immunologically high-risk patients with pre-existing DSAs.

Molecular mechanisms of receptor-mediated endocytosis in the renal proximal tubular epithelium.

Receptor-mediated endocytosis is a pivotal function of renal proximal tubule epithelial cells (PTECs) to reabsorb and metabolize substantial amounts of proteins and other substances in glomerular filtrates. The function accounts for the conservation of nutrients, including carrier-bound vitamins and trace elements, filtered by glomeruli. Impairment of the process results in a loss of such substances and development of proteinuria, an important clinical sign of kidney disease and a risk marker for cardiovascular disease. Megalin is a multiligand endocytic receptor expressed at clathrin-coated pits of PTEC, playing a central role in the process. Megalin cooperates with various membrane molecules and interacts with many intracellular adaptor proteins for endocytic trafficking. Megalin is also involved in signaling pathways in the cells. Megalin-mediated endocytic overload leads to damage of PTEC. Further studies are needed to elucidate the mechanism of megalin-mediated endocytosis and develop strategies for preventing the damage of PTEC.

Megalin and nonmuscle myosin heavy chain IIA interact with the adaptor protein Disabled-2 in proximal tubule cells.

Megalin plays a critical role in the endocytosis of albumin and other filtered low-molecular-weight proteins. Here we studied the interaction between megalin and Disabled-2 (Dab2), an adaptor protein that binds to the cytoplasmic domain of megalin and appears to control its trafficking. We co-immunoprecipitated megalin and Dab2 from cultured proximal tubule cells and identified the proteins by liquid chromatography and tandem mass spectrometry. We found two proteins associated with the megalin/Dab2 complex, nonmuscle myosin heavy chain IIA (NMHC-IIA) and beta-actin. Subcellular fractionation followed by sucrose velocity gradient separation showed that megalin, Dab2, and NMHC-IIA existed as a complex in the same endosomal fractions. In vitro pull-down assays demonstrated that NMHC-IIA was bound to the carboxyl-terminal region of Dab2, but not to megalin's cytoplasmic domain. We then transfected COS-7 cells with plasmids that induced the expression of Dab2, NMHC-IIA, and the megalin minireceptor, a truncated form of megalin. Co-immunoprecipitation studies showed that the minireceptor and NMHC-IIA co-immunoprecipitated only with Dab2. Furthermore, the uptake of (125)I-lactoferrin, an endocytic ligand of megalin, by rat yolk sac-derived megalin-expressing L2 cells was inhibited by blebbistatin, a specific inhibitor of nonmuscle myosin II. Our study shows that NMHC-IIA is functionally linked to megalin by interaction with Dab2 and is likely involved in megalin-mediated endocytosis in proximal tubule cells.

Remission of light chain proximal tubulopathy in IgG λ-type multiple myeloma by lenalidomide and dexamethasone therapy.

Light chain proximal tubulopathy is a rare manifestation of monoclonal gammopathy. A 73-year-old Japanese woman was noted to have urinary protein and hypertension on health examination and visited the regional clinic. She was noted to have IgG λ M protein and suspected of multiple myeloma. She was referred to us with massive proteinuria (7.5 g/g creatinine) and Bence Jones proteinuria without renal dysfunction. A renal biopsy revealed no glomerular abnormalities, but a tubular cast was observed partially in tubules without tubular atrophy or a crystalline structure. Direct Fast Scarlet staining was absent both in glomerulus and vascular wall. Immunofluorescence revealed λ light chain (LC) staining in the proximal tubules. Electron microscopy revealed nonspecific findings including increased lysosomes with irregular contours and mottled appearance. A bone marrow biopsy revealed plasma cell proliferation (35%) and multiple myeloma immunoglobulin G λ type. She showed progressive anemia and decrease of eGFR with elevated level of urinary ß-2 microglobulin. She was treated with lenalidomide + dexamethasone (Ld). With Ld therapy, she achieved hematologic and nephrologic remission reducing the free LC, λ/κ ratio, urinary protein level, and urinary ß-2 microglobulin level.

Role of megalin, a proximal tubular endocytic receptor, in calcium and phosphate homeostasis.

Megalin is expressed at the apical membranes of proximal tubule cells, acting as an endocytic receptor for a variety of ligands filtered by glomeruli. Megalin, also known as a Ca(2+)-binding receptor, is thought to be involved in systemic and intrarenal calcium and phosphate homeostasis. The complex of 25(OH)D(3) and vitamin D-binding protein is endocytosed via megalin into proximal tubule cells, leading to the activation of 25(OH)D(3) to 1, 25(OH)D(3) in the cells. Megalin knockout mice revealed impaired osteogenesis due to vitamin D deficiency. Megalin is also involved in the metabolism of parathyroid hormone and the regulation of the sodium phosphate cotransporter NaPi-IIa. Decreased expression of megalin may be associated with the pathogenesis of hyperphosphaturia observed in patients with Dent's disease. Further studies will elucidate more detailed roles of megalin in pathological states and the mechanisms for interacting with other molecules for the endocytic functions.

Functional characterization of a novel missense CLCN5 mutation causing alterations in proximal tubular endocytic machinery in Dent's disease.

BACKGROUND/AIMS: Mutations of the endosomal chloride/proton exchanger gene, CLCN5, cause Dent's disease, an X-linked recessive proximal tubular disorder. The renal endocytic system was found to be affected in clcn5 knockout mice. However, the impaired endocytic machinery of Dent's disease patients has not been thoroughly investigated. METHODS: The CLCN5 gene was sequenced in a Japanese patient with Dent's disease and his family. The loss-of-function phenotype of the missense CLCN5 mutation was investigated by gene expression in Xenopus oocytes and CHO cells. Immunohistochemical analysis was performed on kidney biopsy specimens for endocytic machinery proteins, megalin, cubilin, and disabled-2 (Dab2) in proximal tubules. RESULTS: Genomic analysis revealed a novel G-to-A transition at the first nucleotide of the 333rd codon of CLCN5, causing a substitution of glycine with arginine. Inefficient expression of the mutant gene in Xenopus oocytes resulted in abolished chloride currents. Impaired N-glycosylation of the mutant protein was evident in the DNA-transfected CHO cells. Proximal tubular expression of megalin, cubilin, and Dab2 was markedly reduced and irregular staining in some portions was observed in the patient compared with controls. CONCLUSIONS: A novel G333R CLCN5 mutation caused defective expression of megalin, cubilin, and Dab2 in a patient with Dent's disease.

The adaptor protein ARH escorts megalin to and through endosomes.

Megalin is an endocytic receptor that binds multiple ligands and is essential for many physiological processes such as brain development and uptake of proteins by the kidney tubule, yolk sac, and thyroid. The cytoplasmic tail of megalin contains two FXNPXY motifs. Autosomal recessive hypercholesterolemia (ARH) is an adaptor protein that binds to the FXNPXY motif of the low-density lipoprotein receptor as well as clathrin and AP-2. We found that ARH also binds to the first FXNPXY motif of megalin in two-hybrid, pull-down and coimmunoprecipitation assays. ARH colocalizes with megalin in clathrin coated pits and in recycling endosomes in the Golgi region. When cells are treated with nocodazole, the recycling endosomes containing megalin and ARH disperse. On internalization of megalin, ARH and megalin are first seen in clathrin coated pits followed by sequential localization in early endosomes and tubular recycling endosomes in the pericentriolar region followed by their reappearance at the cell surface. Expression of ARH in Madin-Darby canine kidney cells expressing megalin mini-receptors enhances megalin-mediated uptake of 125I-lactoferrin, a megalin ligand. These results show that ARH facilitates endocytosis of megalin, escorts megalin along its endocytic route and raise the possibility that transport through the endosomal system is selective and requires interaction with specific adaptor proteins.