Chowdhury, Raad

Abstract Monoclonal gammopathy of undetermined significance (MGUS) is commonly encountered in older individuals. MGUS, by definition, is a benign finding where an expanded population of clonal plasma and B-cells produces a monoclonal antibody that is a biologically inactive. Even in patients with overt plasma cell neoplasms such as multiple myeloma, the monoclonal antibody is often a marker of disease burden but not pathogenic except in light chain cast nephropathy. However, there is a growing recognition that, in rare cases, clonal cells and/or monoclonal gammopathy not meeting criteria for hematologic malignancy can be pathogenic drivers of disease. These MGUS syndromes have been termed monoclonal gammopathies of clinical significance (MGCS), a larger umbrella under which sits the monoclonal gammopathies of renal significance (MGRS). In this review, we focus on MGCS entities beyond standard MGRS and provide a mechanism-based classification centered on the pathogenic nature of the paraprotein rather than on clonal disease burden. We highlight MGCS entities of relevance to nephrologists, including POEMS syndrome, TEMPI syndrome, monoclonal gammopathy-associated systemic capillary leak syndrome, and hematologic autoantibody-mediated disorders. Awareness and recognition of these rare processes are ultimately essential for accurate diagnosis and patient management.

Background: Vascular endothelial growth factor inhibitors (VEGF-I) are frequently used for cancer treatment. VEGF-I can cause proteinuria and acute kidney injury (AKI) with thrombotic microangiopathy (TMA) as a commonly described pathology, but other glomerular pathologies are not well characterized. We aim to describe the clinical characteristics and glomerular lesions associated with VEFG-I in a single center cohort. Methods: We performed a retrospective chart review of patients treated with VEGF-I and underwent kidney biopsies from 2010 to 2022 at the Mayo Clinic, Rochester, MN. Biopsy findings were reviewed by our pathologists. Data on patients’ characteristics, clinical course, and outcomes were abstracted. Descriptive statistics were used to report relevant patient characteristics and findings. Results: From 2010 to 2022, 19 kidney biopsies were performed for kidney dysfunction in patients on VEGF-I. Eleven had complete data, with a median age of 62 years (interquartile range 58–66 years); renal cell carcinoma (RCC) was the most common cancer (4 of 11 patients). TMA was noted in 8 of the 11 biopsies, with proteinuria as the most frequent indication for biopsy in these cases. Three patients had findings other than TMA. One developed anti-phospholipase A2 receptor negative membranous nephropathy; VEGF-I and pembrolizumab were discontinued, and prednisone improved proteinuria. Another patient had known cryoglobulinemia with nephrotic range proteinuria which was exacerbated by VEGF-I peaking at 11 g/day. Despite stopping VEGF-I and treating with prednisone and rituximab, kidney dysfunction progressed to end stage kidney disease (ESKD). A third patient had IgA nephropathy with concurrent diabetic changes, but proteinuria progressed even after stopping VEGF-I. Conclusion: In this case-series of patients treated with VEGF-I undergoing kidney biopsy, we describe the pathological characteristics, clinical course, and outcomes of patients with pathologies other than TMA. Our study adds information to the sparse literature on patients with renal dysfunction after receiving VEGF-I.

ABSTRACT Clonal hematopoiesis of indeterminate potential (CHIP) is a non-malignant state characterized by hematopoietic stem cells exhibiting clonality driven by acquired mutations during aging. Using next-generation sequencing, it has been reported that the prevalence of CHIP increases exponentially with age. Thus far, epigenetic mutations including DNMT3A, TET2 and ASXL1 are the most common mutations identified in driving CHIP. CHIP is considered a pre-malignant state, however with reports of its associations with non-malignant disease states, the clinical impact of CHIP has been of great interest, in particular its effect on the renal and cardiac systems. CHIP has been associated with a higher rate of estimated glomerular filtration rate decline and increased risk of acute kidney injury. CHIP and its driver mutations have also been shown to increase cardiovascular disease and atherosclerosis through various inflammatory pathways. In this review, we discuss the pathophysiology of CHIP through aging, its impact on kidney disease and implications on cardiovascular health. We also compare CHIP to another pre-malignant clonal disorder, monoclonal gammopathy of undetermined significance (MGUS).

Introduction: Monoclonal gammopathy of renal significance (MGRS) is characterized by clonal cell deposition of monoclonal immunoglobulin causing renal manifestations without overt malignancy. MIDD is a subtype of MGRS characterized by deposition of monoclonal light (LCDD), heavy chains (HCDD), or both (LHCDD) along the renal glomerular and tubular basement membranes. Virtually all organs can be involved, and if left untreated, MIDD can progress to MM and end stage renal disease. Although these patients classically did not receive treatment, current MIDD management is primarily focused on controlling the underlying clonal plasma cell disorder. Case description: We present a 56-year-old male with atypical MIDD treated successfully with plasma cell directed therapy consisting of daratumumab, cyclophosphamide, bortezomib, and dexamethasone (DARA-CYBOR-D). Despite a primary diagnosis of diabetic kidney disease, renal biopsy suggested myeloma-related MIDD based on linear immunofluorescent staining for IgG and kappa light chains along the tubular and glomerular basement membranes. Notably there were no electron dense deposits in the mesangium or tubular basement membranes typical to MIDD electron microscopy. Despite the presentation of MIDD on IF only, DARA-CYBOR-D treatment led to hematologic and renal improvement and remission from MIDD, with a GFR increase from 22 to 59 mL/min/BSA and a drop in urine protein from up to 9 to 0.6 g/dL. Conclusions: In conclusion, our case illustrates the efficacy of the DARA-CYBOR-D regimen in a patient with IF-only MIDD. We highlight the importance of obtaining a kidney biopsy when there are other potential causes for real decline and enhance our understanding of pathological and clinical spectrum of MIDD.

Abstract Background and Aims Immune-checkpoint inhibitors (ICI) are antineoplastic therapies that unleash the immune-system and have revolutionized cancer outcomes. Though they are a drug class with great potential, their effects are not always limited to the malignant cells and can cause a spectrum of immune-related adverse events (irAEs). Roughly 5% of patients will experience acute kidney injury (AKI) with acute interstitial nephritis (AIN) being the predominant pathologic lesion. Glomerular and vascular lesions are thought to be rare and, as a result, not well-defined. We aim to document glomerular and vascular pathology in this context at our institution. Method We performed a retrospective review of internal native renal biopsies from 2010-2022 that had known ICI treatment. Standard processing of renal biopsies included light microscopy (LM), immunofluorescence (IF), and electron microscopy (EM). We reviewed the biopsies and pathology reports, as well as clinical data from patient electronic medical records. Results Our search yielded 32 kidney biopsies; of those, most had AIN (27/32), 8 cases had glomerular pathology, and 1 case had arterial endotheliitis. Of the cases with glomerular pathology, 4 had subacute glomerular thrombotic microangiopathy (TMA). Among the cases with TMA, 2 were also treated with vascular endothelial growth factor inhibitor (VEGFi),1 with gemcitabine, and 1 with BRAF-inhibitor therapy. Further, only one of these patients had complement testing, which did not reveal definitive deficiency. One patient had proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID), IgG-κ. One patient had IgA nephropathy (IgAN) and another had membranous nephropathy (MN). Most patients were biopsied for rising serum creatinine (SCr) (median: 1.6 mg/dL; range: 0.55-5.5); 1 had nephrotic-range proteinuria (median urine protein/creatinine ratio (UPCR): 0.3; range: 0.12-5.64). One, with thin basement membrane disease, had significant hematuria (>100 RBC/hpf). Five patients had irAEs in other organs. 7/9 patients died or entered hospice care (median: 14 months post-biopsy; range: 2-48 months) due to malignancy progression. Of the deceased patients, 2 were dialysis-dependent. Of the living patients, 1 has dialysis-independent chronic kidney disease (CKD). Conclusion Overall, glomerular and vascular pathology due to ICI-use appears rare though difficult to isolate since other drugs and neoplasia can cause similar lesions. In our cohort, TMA was the most common glomerular lesion, though direct causation due to ICI is difficult to prove. In all patients with TMA, we identified concurrent use of other known causative drugs. IgAN and MN have been reported in association with neoplasia. PGNMID has been reported in a variety of malignant and nonmalignant conditions, and ICI-use could be a triggering factor. In conclusion, the patterns of glomerular injury seen in our cohort may be secondary to other concurrent risk factors other than ICI use. Arterial endotheliitis appears to be a rare but significant secondary effect to ICI-use.