Published papers

Background: Cytotoxic T lymphocyte antigen-4 (CTLA-4) is an essential inhibitory regulator of immune activation. CTLA-4 haploinsufficiency is known to be associated with dysregulation of FOXP3+ regulatory T cells, hyperactivation of effector T cells, and lymphocytic infiltration of multiple organs. However, there have only been a few reports of renal involvement with CTLA-4. Herein, we present a case of acute granulomatous tubulointerstitial nephritis (TIN) in a patient with CTLA-4 haploinsufficiency. Case presentation: A 44-year-old man presented with a 3-week history of fever and malaise, and subsequently developed acute kidney injury (AKI) a few days after treatment with levofloxacin (LVFX). A kidney biopsy and immunohistochemical staining revealed granulomatous TIN with dominantly infiltrating CD4+ T cells. General symptoms and renal impairment showed improvement after discontinuation of LVFX and initiation of oral steroids. However, they worsened following steroid tapering. Further, a colon biopsy analysis showed similar findings to the renal tissue analysis. We suspected that granulomatous TIN was possibly associated with CTLA-4 haploinsufficiency. Therefore, the patient was transferred to another hospital for further treatment of CTLA-4 haploinsufficiency using immunosuppressive agents. Conclusions: There have been few reports regarding renal involvement of CTLA-4 haploinsufficiency. In the present case, granulomatous TIN could have arisen due to instability of immune regulatory functions, such as CTLA-4 haploinsufficiency, and treatment with LVFX could have triggered immunologic activation and severe inflammation as well as renal dysfunction.

An 84-year-old man developed a membranoproliferative glomerulonephritis pattern of injury, and the most likely cause detected during a workup was monoclonal IgG-λ in the urine and serum. Predominant IgG and λ light chain deposition was confirmed only by immunofluorescence using formalin-fixed, paraffin-embedded tissue and not by immunohistochemistry. A smaller and non-linear dynamic range of immunohistochemistry makes it less quantitative than immunofluorescence staining and may explain why immunohistochemistry failed to detect the light chain restriction. This case suggests that immunohistochemistry may not serve as a substitute for immunofluorescence on formalin-fixed, paraffin-embedded tissue in detecting masked monoclonal immunoglobulin deposits, although further research is warranted.

A 50-year-old man presented to our hospital with a fever, edema, and a rash. The clinical diagnosis was renal dysfunction, nephrotic syndrome, and syphilis. The patient was treated with benzylpenicillin, and his symptoms improved. A renal biopsy revealed membranous nephropathy (MN). Recently, neuron-derived neurotrophic factor (NDNF) was reported to be an antigen corresponding to syphilis-associated MN. In the present patient, immunofluorescence staining and immunoelectron microscopy revealed granular NDNF-positive findings within subepithelial deposits, suggesting the presence of NDNF-IgG immune complexes. Although the mechanism by which NDNF serves as a target antigen remains unclear, NDNF was found to colocalize within subepithelial immune complexes in syphilis-associated MN.

Antiglomerular basement membrane (GBM) disease has a poor prognosis. The rapid detection of serum anti-GBM antibody using an enzyme immunoassay, which has a high sensitivity and specificity, leads to an early diagnosis and improved prognosis. We report a case of acute kidney injury with false-positive anti-GBM antibody. A man in his early fifties underwent aortic arch replacement using bovine serum albumin (BSA)-containing surgical adhesion. After intravenous administration of vancomycin for a fever, he developed acute kidney injury without an abnormal urinalysis, and his anti-GBM antibody titer (fluorescence enzyme immunoassay [FEIA]) was 70.4 IU/mL. A kidney biopsy showed acute tubular injury and minor glomerular abnormalities without immunoglobulin G deposits, suggesting no evidence of anti-GBM glomerulonephritis. Consistent with the false-positive anti-GBM antibody test results, anti-GBM antibody determined using a chemiluminescent enzyme immunoassay was negative. A serum sample showed crossbinding to the FEIA plate from which the GBM antigen was removed. This finding indicated a nonspecific reaction to BSA, which contains a coating solution for the FEIA plate. This reaction was likely caused by anti-BSA antibody produced using BSA-containing surgical adhesion. Our findings suggest emerging challenges in diagnosing anti-GBM disease. Nephrologists must remain vigilant regarding false-positive anti-GBM antibody test results, particularly in cases evaluated with immunoassays that contain BSA.

Cyanotic congenital heart disease is occasionally associated with kidney dysfunction, which is known as cyanotic nephropathy or cyanotic glomerulopathy. The clinical presentation of cyanotic nephropathy includes proteinuria, decreased estimated glomerular filtration rate, hyperuricemia, thrombocytopenia, or polycythemia. Although advances in surgical procedures have improved the prognosis of cyanotic congenital heart diseases, adult cases of cyanotic nephropathy are still rare, and there are few reports of kidney biopsy in adults with cyanotic nephropathy. Here, we present the case of a 41-year-old patient with Fontan palliation who developed nephrotic range proteinuria and had a kidney biopsy, which showed glomerular hypertrophy with segmental glomerulosclerosis around vascular poles, suggesting adaptive focal segmental glomerulosclerosis. This case provides further understanding of kidney dysfunction due to cyanotic congenital heart disease and shows the need for attention in the management for prevention of progression to end-stage renal disease and in the selection of renal replacement therapy.

We report the case of a 73-year-old-man who developed immunotactoid glomerulopathy (ITG). ITG is a rare disease characterized by proliferative glomerulonephritis and capillary wall deposits with a 10-60 nm diameter microtubular substructure. In monoclonal ITG, immunofluorescence analysis typically exhibits IgG with light chain restriction. Recent reviews recommend distinguishing monoclonal ITG from polyclonal ITG because monoclonal ITG is associated with a higher incidence of hematological disorders and better responsiveness to clone-directed therapy and renal prognosis. In our case, IgG, IgA, and IgM were negative by routine immunofluorescence; however, immunoelectron microscopy revealed positive λ chain. At 6 months after renal biopsy, the IgG λ chain was detected in the serum and urine, reflecting possible monoclonality. Therefore, it is useful to perform immunoelectron microscopy and follow-up with serum and urine protein electrophoresis and immunofixation to diagnose monoclonal ITG, even when routine immunofluorescence shows negative or nonspecific findings.

Recent epigenome-wide studies suggest an association between blood DNA methylation and kidney function. However, the pathological importance remains unclear. Here, we show that the homing endonuclease I-PpoI-induced DNA double-strand breaks in kidney glomerular podocytes cause proteinuria, glomerulosclerosis, and tubulointerstitial fibrosis with DNA methylation changes in blood cells as well as in podocytes. Single-cell RNA-sequencing analysis reveals an increase in cytotoxic CD8+ T cells with the activating/costimulatory receptor NKG2D in the kidneys, which exhibit a memory precursor effector cell phenotype, and the CD44high memory CD8+ T cells are also increased in the peripheral circulation. NKG2D blockade attenuates the renal phenotype caused by podocyte DNA damage. Blood methylome shows increased DNA methylation in binding sites for STAT1, a transcription factor contributing to CD8+ T cell homeostasis. Collectively, podocyte DNA damage alters the blood methylome, leading to changes in CD8+ T cells, which contribute to sustained renal injury in chronic kidney disease.

Membranous nephropathy (MN) recurs in some kidney allograft patients, and recurrence increases graft failure rates. We present a unique case of recurrent MN in first and second allografts showing glomerular capillary wall-positivity for complement receptor 1 (CR1) consistent with immunoglobulin G (IgG). A man in his late 20s developed MN and started hemodialysis. MN recurred and caused graft loss after the first transplantation and recurred again soon after the second transplantation. The IgG subclass staining was almost consistently negative for IgG4 and phospholipase A2 receptor (PLA2R)-staining was negative. Recurrent MN of unknown etiology was considered. Mass spectrometry demonstrated that CR1 had increased in the transplanted kidney biopsies. Immunohistochemistry and immunofluorescence studies demonstrated CR1 colocalized with IgG along glomerular capillaries in this case, whereas CR1 was localized in podocytes with no colocalization of IgG in a control case of PLA2R-associated MN. Correlative light and immunoelectron microscopy showed localization of CR1 at the interface between electron-dense deposits and podocytes. Collectively, this case demonstrated a unique enhancement and localization of CR1. MN with enhancement of CR1 has not been reported to date. CR1 may be a candidate causative antigen in this case of recurrent MN, although further study is needed to investigate the pathogenesis of CR1.

Mutations in the ciliary gene TTC21B, NPHP4, and CRB2 cause familial focal and segmental glomerulosclerosis (FSGS). We report a girl with a mutation of the ciliary gene CC2D2A presenting with FSGS and nephronophthisis. The patient had mental retardation, postaxial polydactyly, and ataxic breathing, and was diagnosed as having compound heterozygous CC2D2A missense mutations at age 5. Retrospectively, azotemia at 1 year and proteinuria at 5 years were recorded but not investigated. At age 6, she was referred to the pediatric nephrology service because of hypertension, pretibial pitting edema, heavy proteinuria, and hematuria. eGFR was 66 ml/min/1.73 m2, total protein 5.3 g/dl, albumin 2.4 g/dl, and cholesterol 317 mg/dl. Ultrasonography showed normal-sized kidneys with a cyst in the right. Losartan was started. On renal biopsy, 8 out of 24 glomeruli were globally sclerosed, and three showed segmental sclerosis and/or hyalinosis with no immune deposits. Mild tubular dilatation, tubular atrophy, and interstitial fibrosis were observed. On electron microscopy, glomeruli showed focal foot process effacement with no electron dense deposits. Since losartan did not exert an obvious effect, treatment with prednisolone was tried. Urine protein decreased from 6.6 to 3.7 g/gCr. Prednisolone was discontinued after 10 days, however, because she developed duodenal ulcer perforation that necessitated omentoplasty. Subsequently, she was treated with losartan only. Her renal function deteriorated and peritoneal dialysis was initiated 8 months later. FSGS in this patient could be primary glomerular associated with CC2D2A mutation, rather than the consequences of tubulointerstitial fibrosis.

Glomerulopathy associated with shunt infection is commonly membranoproliferative glomerulonephritis, whereas the causative organisms of secondary membranous nephropathy are usually viruses. We report a case of membranous nephropathy associated with shunt infection. The patient was born at 29-week gestation with a birth weight of 1178 g. Ventriculoperitoneal shunt surgery had been performed for congenital hydrocephalus. Thereafter, she had experienced seven shunt infections. At the age 13 years, proteinuria was detected in a school urinary screening. Urinalysis at our hospital demonstrated 3 + protein and 3 + blood. Laboratory testing demonstrated a serum creatinine 0.5 m/dl, albumin 2.5 g/dl, C-reactive protein (CRP) 13.7 mg/dl, and C3 182 mg/dl. Prior to repeat urinalysis, the patient developed vomiting and was admitted with suspected shunt infection. On admission, her body temperature was 36.0 ºC. Physical examination was unremarkable other than small stature and a palpable mass in the left upper quadrant. Urinalysis demonstrated 2 + protein and 1 + blood with no cells or casts. The urinary protein excretion was 3 g/day. Abnormal laboratory tests included erythrocyte sedimentation rate 102 mm/hr, CRP 11.67 mg/dl, IgG 2442 mg/dl, C3 177 mg/dl, and C4 44 mg/dl. Antibiotic therapy was initiated for a presumptive diagnosis of shunt infection and the shunt catheter was removed. Cultures obtained after antibiotic administration were negative. Proteinuria persisted after control of the shunt infection. Histology of a renal biopsy demonstrated membranous nephropathy with diffuse granular IgG staining and subepithelial deposits. Three possible pathomechanisms for her membranous nephropathy were considered.

Idiopathic multicentric Castleman disease (iMCD) is a systemic and polyclonal lymphoproliferative disease involving multiple organs, including the kidneys, due to the overproduction of interleukin-6 (IL-6). Recently, several reports have suggested that excessive IL-6 actions in iMCD could have a causal relationship with the development of diverse histopathological renal manifestations that cause nephrotic syndrome. However, the treatment for such cases remains unclear. We report a series of three cases of nephrotic syndrome due to iMCD that helps to delineate the importance of early and continuous therapy with the anti-interleukin-6 receptor antibody tocilizumab. First, treatment was suspended for infectious control, and the patient presented with nephrotic syndrome due to diffuse mesangial and endocapillary hypercellularity without immune deposits complicating acute kidney injury. Second, iMCD was treated with prednisolone alone. The patient suddenly developed nephrotic syndrome due to immune-complex glomerulonephritis, not otherwise specified, complicated with acute kidney injury. In the third case, nephrotic syndrome secondary to membranous glomerulonephritis was diagnosed, with a skin rash and IgE antibodies to tocilizumab, and was therefore treated with prednisolone alone. In contrast to the first two cases, the third progressed to end-stage renal disease on hemodialysis. Taken together, this series suggests that clinicians should maintain clinical vigilance for iMCD as a possible underlying component of nephrotic syndrome, since iMCD presents with a variety of renal pathologies. Prompt initiation and continuous administration of tocilizumab are likely key determinants of renal outcomes in such cases. In particular, when tocilizumab is suspended due to infection or in the perioperative period, consideration of its expeditious resumption should be made, taking into account both the withdrawal period and systemic conditions.

The common histopathology of antineutrophil cytoplasmic antibody-associated vasculitis comprises pauci-immune crescentic glomerulonephritis with concomitant tubulointerstitial nephritis. Tubulointerstitial nephritis in the absence of glomerular involvement in patients with antineutrophil cytoplasmic antibody-associated vasculitis is uncommon. We report a case of antineutrophil cytoplasmic antibody-associated vasculitis-associated acute kidney injury manifesting as tubulointerstitial nephritis without glomerulonephritis. A 75-year-old woman with fever, cough, and myalgia developed kidney dysfunction with inflammatory reactions and tubular-type proteinuria, without glomerular hematuria. A kidney biopsy revealed tubulointerstitial nephritis with arteritis. We ruled out important underlying etiologies of tubulointerstitial nephritis, including infection, drug reactions, and autoimmune diseases. Since chest high-resolution computed tomography demonstrated mild interstitial pneumonia in bilateral lower lung fields, myeloperoxidase antineutrophil cytoplasmic antibody was measured and found to be positive. Therefore, we diagnosed the patient with antineutrophil cytoplasmic antibody-associated vasculitis-associated tubulointerstitial nephritis but not glomerulonephritis, and interstitial pneumonia. The patient's kidney function and symptoms markedly improved with prednisolone treatment. Clinicians should maintain high-level vigilance for antineutrophil cytoplasmic antibody-associated vasculitis as a possible underlying component of tubulointerstitial nephritis, particularly when kidney function deteriorates with tubulointerstitial injuries without glomerular features.

Efficacy of systemic corticosteroid therapy (CS) for long-term kidney survival in patients with IgA nephropathy (IgAN) is controversial. Therefore, prospective studies evaluating targeted therapies to lymphatic tissues in mucosal immune system responsible for production of nephritogenic IgA have been desired worldwide. Here, we aimed to evaluate the associations of CS and combination therapy of CS and tonsillectomy (CS + Tx) with kidney survival, using database from a nationwide multicenter prospective cohort study on IgAN. Primary outcome was a 50% increase in serum creatinine from baseline or dialysis induction. The analysis included 941 patients (CS/CS + Tx/non-CS 239/364/338), 85 (9.0%) of whom reached outcomes during median follow-up of 5.5 (interquartile range 2.0-8.0) years. On overlap weighting analysis with balanced baseline characteristics, CS and CS + Tx were associated with lower risk of kidney events when compared with non-CS (hazard ratio [HR] 0.51, 95% confidence interval [CI] 0.29-0.88 and HR 0.20, 95%CI 0.09-0.44, respectively). Notably, when compared with the CS, CS + Tx was associated with a lower risk of kidney events (HR 0.40, 95%CI 0.18-0.91). Present study demonstrated, keeping with favorable association of systemic CS with kidney survival, concurrent tonsillectomy as one of targeted interventions to lymphatic tissues may provide additional improvement to kidney survival in patients with IgAN.

The gut–kidney axis has recently gained attention as a pathogenesis of IgA nephropathy (IgAN). In fact, the efficacy of target-release formulation of budesonide for IgAN has been reported in recent studies. On the other hand, there have been no reports yet on the efficacy of enteric-coated budesonide for IgAN complicated with inflammatory bowel disease. We report a case of IgAN with comorbid Crohn’s disease (CD) treated with a combination of enteric-coated budesonide and methylprednisolone pulse therapy. The patient was followed for 2 years. He showed initial reduction in proteinuria following treatment. However, after discontinuation of enteric-coated budesonide therapy, proteinuria recurred despite well-controlled CD. Enteric-coated budesonide combined with methylprednisolone pulse therapy may be effective in short-term reduction of proteinuria while minimizing systemic steroid side effects in IgAN associated with CD. However, the tendency for relapse suggests the need for long-term management strategies. Therefore, further research is needed to establish optimal treatment protocols for this patient population.

Although the coronavirus disease 2019 (COVID-19) vaccine has been proven to be effective and safe in most adults and children, various diseases, including IgA nephropathy, sometimes occur as an adverse effect. We herein describe a case of IgA nephropathy in a 16-year-old, male patient with persistent kidney dysfunction following COVID-19 vaccination and present the clinicopathological course of the disease. The patient presented to the outpatient clinic with a history of gross hematuria 6 days after receiving the COVID-19 vaccine. Prior to the current presentation, he was being examined regularly at an outpatient clinic for asymptomatic hematuria. His mother had received a diagnosis of IgA nephropathy, and his younger brother had received a diagnosis of asymptomatic hematuria. A blood test of this patient demonstrated elevated serum creatinine, and IgA nephropathy was pathologically diagnosed (Oxford classification M0E1S1T0C1). Prednisolone and immunosuppressants were administered promptly to treat the decreased kidney function and the pathology. Nevertheless, the failure of his kidney function to recover to the state it was in prior to this episode may have led to the formation of chronic lesions, causing irreversible kidney tissue damage. Some patients with IgA nephropathy, asymptomatic hematuria or a family history of kidney-related symptoms may experience kidney dysfunction after COVID-19 vaccination and require prednisolone or immunosuppressive therapy to stem the progressive deterioration of their kidney function. Prior to receiving the COVID-19 vaccine, patients with any of these conditions should be provided with an appropriate explanation of the risks and be asked for their consent to be vaccinated.

当院において,コントロール不良の2型糖尿病および間質性肺炎を併存する高齢男性に生じた急速進行性糸球体腎炎(rapidly progressive glomerulonephritis:RPGN)で腎生検組織所見から感染後糸球体腎炎合併ANCA関連糸球体腎炎と診断した症例を経験した.プレドニゾロン(prednisolone:PSL)およびリツキシマブ(rituximab:RTX)で寛解導入療法を行うも腎機能が改善せず,維持血液透析療法導入となった.その後の寛解維持療法の継続により重篤な感染症を呈することなくステロイドを投与終了し残存腎機能の回復を認め,RTXの寛解維持治療中に透析導入後11ヵ月で透析離脱となった.高齢かつ合併症の多いANCA関連血管炎におけるRPGNにおいても,腎予後良好な徴候がみられた場合には適切な感染症予防を行ったうえでRTX療法を継続することで透析離脱が可能となる場合がある.(著者抄録)