Hydralazine use can be associated with IgM-dominated immune complex-mediated glomerulonephritis.

CONTEXT: IgM-dominant immune complex-mediated glomerulonephritis (IgM-dominant ICMGN) is a rare renal entity, characterized by a membranoproliferative pattern by light microscopy, dominant IgM staining by immunofluorescent staining, and subendothelial deposits by electron microscopy. This study was to investigate if some of IgM-ICMGN were associated with autoimmune disorders induced by hydralazine. DESIGN: Seven IgM-dominant ICMGN cases were identified over 8 years. Their pathologic phenotypes and clinical scenarios were analyzed in detail. RESULTS: Patients' ages ranged from 47 to 87 years old with 5 women and two men. Six of seven patients had drug-induced autoimmune phenomenon (hydralazine-induced positive ANCA and ANA). All of them had renal dysfunction and some proteinuria. Most pathologic features showed a membranoproliferative pattern of glomerulonephritis with dominant IgM deposits at subendothelial spaces. IgM nephropathy (a variant of focal segmental glomerulosclerosis), chronic thrombotic microangiopathy, and cryoglobulinemic glomerulopathy were ruled out in the cases. CONCLUSION: The hydralazine-induced autoimmune phenomenon can be seen in IgM-dominant ICMGN, which should be classified as a subtype of membranoproliferative glomerulonephritis.

The Role of Bone Marrow Biopsy Evaluation in the Workup for Monoclonal Gammopathy of Renal Significance: A Diagnosis of Exclusion.

CONTEXT.­: Monoclonal gammopathy of renal significance (MGRS) is a relatively new concept for patients with renal monoclonal protein deposition (RMPD) (except monoclonal cast nephropathy) and has been used as a reason for nephrologists to obtain a bone marrow biopsy (BMB). It takes a team of pathologists and clinicians to determine when RMPD at our institution can be defined as MGRS. OBJECTIVE.­: To identify the proportion of various subtypes of tentative MGRS diagnosed by renal biopsy that can be confirmed as final MGRS after BMB. DESIGN.­: One hundred thirty kidney biopsies with variants of RMPD were identified during the past 10 years. Biopsy cases with known myeloma, B-cell lymphoma, or monoclonal cast nephropathy were separated as a heavy-burden group. The remaining biopsies with RMPD were considered tentative MGRS. Their BMB and clinical indices were further analyzed to determine the final percentage of MGRS diagnoses. RESULTS.­: Among the 130 renal paraprotein deposition cases, 44 (33.8%) were categorized as the heavy-burden group. In the remaining 86 cases, 33 (38.4%) with subsequent identification of myeloma (>10% of monoclonal plasma cells) or lymphoma in BMB were further considered as heavy-burden cases. Eighteen cases (18 of 86; 20.9%) did not receive follow-up BMB; thus, no further analysis was performed. BMBs diagnosed as either nonmalignant (no plasma cells; 8 of 86 cases; 9.3%) or premalignant (<10% plasma cells; 27 of 86 cases; 31.4%) were confirmed to be final MGRS (35 of 86; 40.7%). CONCLUSIONS.­: The data indicate that BMB is an important element in the confirmation of MGRS.

Clear cell renal cell carcinoma cells show diffuse expression of phagocytotic markers through the identification of lysosome-rich eosinophilic granules.

BACKGROUND: Paneth cell-like granules (PCLG) in clear cell renal cell carcinomas (RCC) have previously been reported but were not found to express neuroendocrine markers. This study was to investigate if the eosinophilic granules (so called PCLG) were enlarged lysosomes. METHODS: A retrospective review of 72 different renal tumors was conducted which included 42 clear cell RCC, 16 papillary RCC, 6 chromophobe RCC, 5 clear cell papillary RCC, 2 urothelial carcinomas and 1 unclassified RCC. All tumors were evaluated for the eosinophilic granules on hematoxylin and eosin-stained sections. In addition, PAS-D staining, immunohistochemical stains, and electron microscopy were performed. RESULTS: The eosinophilic granules were found in 19% (8 out of 42) clear cell RCC, but not in the other renal tumor types. The granules stained positively for PAS-D and were also positive for lysosomal protein markers CD68 and lysozyme. Electron microscopy revealed that the eosinophilic granules were smooth ball-shaped structures in the cytoplasm, ranging in size from 0.8 to 1.4 µm. The overall findings indicate that the eosinophilic granules were best correlated with lysosomes. CONCLUSIONS: The eosinophilic granules in clear cell RCC are expanded lysosomes, and this may be used as a unique feature for confirming the pathologic diagnosis of clear cell RCC. The findings further support the view that clear cell RCC have phagocytic capacity due to their containing abundant lysosomes in the cytoplasm.

Punctate IgG staining particles localize in the budding ballooning clusters of reactive foot processes in minimal change disease.

The etiology of minimal change disease (MCD) remains a mystery as the only characteristic findings are the diffuse effacement of foot processes seen on electron microscopy (EM). Punctate IgG staining found floating outside glomerular capillary loops in MCD cases was recently identified as autoimmune antibodies against nephrin of podocytes. We hypothesized that the punctate IgG staining is located on budding ballooning clusters (BBC) of reactive foot processes in Bowman's space found on EM. We identified seven patients with MCD cases showing IgG staining that were subsequently evaluated for BBC on EM. We concurrently examined 12 negative controls, either unremarkable cases or tubulointerstitial diseases, by EM. Immunogold labeling was performed to confirm the presence of IgG and determine localization. In seven MCD cases, there were positive punctate IgG staining particles outside of the glomerular basement membranes (GBM) along with concurrent punctate staining for C3, kappa, and lambda. By EM, all seven (100%) MCD cases revealed BBC that was characterized by ballooning foot processes ranging from 1 to 6 µm and was either budding or detached from the GBM in 3-7 clusters; no electron-dense materials were seen in BBC. BBC was also seen in only 1 of 12 (8%) negative controls. Immunogold labeling identified IgG particles within BBC of MCD by EM, but not in the negative control. Our data suggest that BBC are EM structures of reactive foot processes that are most likely correlated with punctate IgG staining seen in cases of MCD, supported by immunogold labeling for IgG.

Myeloperoxidase Staining Identifies Endothelial Injury of Peritubular Capillaries and Glomeruli in Renal Antibody-Mediated Rejection.

OBJECTIVE: It remains unclear if C4d staining is related to any peritubular and glomerular injury during antibody mediated rejection (ABMR). The goal of this study was to determine if myeloperoxidase (MPO) staining can highlight endothelial injury in peritubular capillaries (PTC) and glomeruli. METHODS: The study included 12 native negative controls, 19 transplant biopsies with borderline changes (BC) as transplant controls, and one group of renal transplant biopsies with ABMR as the study group (acute/chronic, n=22). All three groups were stained for MPO immunohistochemically, and the MPO expressions in the endothelium of PTC and glomeruli were evaluated and correlated with serum creatinine (SCr). In addition, the ultrastructural layers of the PTC (an index for chronic allograft rejection) were correlated with MPO indices in PTC. RESULTS: The negative control group and the transplant controls showed no MPO expression in the endothelium of glomeruli and PTC. However, in the biopsies with ABMR, there were MPO-positive stains in the endothelial cells of glomeruli (15/21 cases, 71.4 %) and PTC (16/22 cases, 72.7 %). There were significant correlations between the peritubular MPO staining versus SCr (r=0.355 and p=0.0106) and glomerular MPO staining versus SCr (r=0.365 and p=0.0092). Furthermore, the layers of PTC by electron microscopy were significantly correlated with MPO scores in PTC (r=0.696, p=0.0001). CONCLUSION: Our data suggest that the MPO-positive endothelial injuries are most likely the cause leading to renal graft dysfunction following ABMR.

Podocytopathies related to either COVID-19 infection or its vaccination, our experience and literature review.

Coronavirus disease 2019 (COVID-19) affects several organs including the kidney resulting in acute kidney injury (AKI) and variants of podocytopathies. From the beginning to the middle period of the COVID-19 pandemic, we have collected eight renal biopsies with various renal diseases including 4 podocytopathies. In addition, from the middle period to the near end of the COVID-19 pandemic, we have seen two of the patients who developed nephrotic syndrome following COVID-19 vaccination. Three of 4 podocytopathies were collapsing glomerulopathy (also called collapsing focal segmental glomerulosclerosis) and the fourth was a minimal change disease (MCD). Two of three collapsing glomerulopathy were found in African American patients, one of who was tested positive for having the high-risk allele APOL-1 G1. In addition, the two renal biopsies showed either MCD or replaced MCD following COVID-19 vaccination. MCD can be a rare complication following COVID-19 infection and COVID-19 vaccination, raising the question if there are similar antigens induced by the infection or by the vaccination that trigger the MCD. This article reports our experience of diagnosing podocytopathies related to either COVID-19 infection or its vaccination and provides a literature review regarding the incidence and potential pathophysiology in the field.

Proteinuria in thrombotic microangiopathy is associated with partial podocytopathy.

BACKGROUND: Thrombotic microangiopathy (TMA) results in acute kidney injury, but the cause of heavy proteinuria in this disorder is puzzling. The goal of this study was to determine if there were significant effacement of foot processes and CD133-positive hyperplastic podocytes in TMA to explain the proteinuria. METHODS: The study included 12 negative controls (renal parenchyma removed from renal cell carcinoma) and 28 thrombotic microangiopathy due to different etiologies. The percent of foot process effacement was estimated, and proteinuria level was obtained for each TMA case. Both groups of cases were stained for CD133 by immunohistochemical method, and the number of positive CD133 in hyperplastic podocytes was counted and analyzed. RESULTS: Nineteen (19) of 28 (68%) TMA cases had nephrotic range proteinuria (urine protein/creatinine >3). Twenty-one (21) of 28 (75%) TMA cases showed positive CD133 staining in scattered hyperplastic podocytes within Bowman's space but was absent in control cases. The percent of foot process effacement (56 ± 4%) correlated with proteinuria (protein/creatinine ratio 4.4 ± 0.6) (r = 0.46, p = .0237) in TMA group. CONCLUSION: Our data indicate that the proteinuria in TMA can be associated with significant effacement of foot processes. CD133-positive hyperplastic podocytes can be seen in the majority of TMA cases of this cohort, indicating a partial podocytopathy.

Review: Mammalian Target of Rapamycin (mTOR) Pathway Is Critical in Developing Most Renal Cell Tumors.

OBJECTIVE: Various renal cell carcinomas (RCC) are derived from different segments of the renal tubular origin, which determines their morphological and immunohistochemical phenotype and their molecular signaling pathway as a therapeutic target. Most of these tumors utilize the mammalian target of rapamycin (mTOR) pathway to activate pathways involving metabolic and nutritional supplies. METHODS: Overexpressed mTOR signals are reported in more than 90% of the most common types of RCC. Many new renal tumor entities have been reported in recent years. RESULTS: Among them, somatic mutations in tuberous sclerosis complex (TSC) result in loss of its normal inhibitory control over mTOR, thus promoting mTOR-associated proliferative activities in several new renal neoplastic entities including RCC with fibromyomatous stroma (RCCFMS), eosinophilic vacuolated tumor, eosinophilic solid & cystic RCC, and low-grade oncocytic tumor. CONCLUSIONS: This short review provides a comprehensive correlation of tumor morphology and immunohistochemical phenotype with renal tubular differentiation and their shared mTOR. These essential pieces of knowledge are vital in the diagnosis and clinical management of renal cell neoplasms.

Immunohistochemical Panels to Evaluate Important Immunophenotypes of Human Mesonephros.

Background. The immunophenotypes and potential excretory function of human mesonephros are not well studied. Methods. Five mesonephros specimens of human embryos from the 6th to 10th weeks of gestation were stained with immunohistochemical markers. Results. PAX8 was universally expressed in all renal tubules, while α-methyacyl-CoA racemase (AMACAR) was positive in proximal tubules and GATA3 was positive in distal tubular mesonephric structures. At the 8th weeks of gestation, the mesonephric glomeruli were characterized by opened glomerular capillary loops with Periodic Acid Schiff (PAS)-positive glomerular basement membranes and GATA3-positive mesangial-like cells. By the 8th week, proximal tubules showed PAS-positive brush borders, indicating reabsorption capacity, and the proximal tubules also demonstrated positivity with kidney injury molecule-1 (KIM-1), representing tubular response to injury. Conclusion. Our overall findings show detailed phenotypes of the glomerular and tubular structures of the mesonephros and indicate that at the 8th week of gestation, the mesonephros may carry out temporary excretory function before metanephros becomes fully functional.

Neutrophil extracellular traps drive lupus flares with acute skin and kidney inflammation triggered by ultraviolet irradiation.

Sunlight triggers lupus flares causing both local skin and systemic inflammation, including lupus nephritis, through poorly understood mechanisms. To address this knowledge gap, we found that UVB irradiation of asymptomatic, young female lupus-prone mice induced skin and kidney inflammation with proteinuria, accompanied by neutrophil infiltration and neutrophil extracellular trap (NET) formation. Furthermore, UVB irradiation induced co-expression of CXCR4 and cytokines/C3 by neutrophils in vitro and in vivo, in the skin and kidneys of lupus-prone mice, indicating their transmigratory and pro-inflammatory potentials. A causality study demonstrated that inhibiting CXCR4 attenuated renal neutrophil infiltration, accumulation of NETs, NET-associated cytokines/C3, and proteinuria in UVB-irradiated lupus-prone mice. Remarkably, inhibiting NETosis through a novel strategy targeting nuclear envelope integrity reduced deposition of NET-associated cytokines/C3 in skin and kidneys, attenuating proteinuria in UVB-irradiated MRL/lpr·lmnB1 Tg mice. Our investigation unveils a new mechanism by which neutrophil NETs drive the early onset of lupus flares triggered by UVB-irradiation. Targeting neutrophil transmigration and NETosis could be promising therapeutic strategies.

Focal Segmental Glomerulosclerosis (FSGS) Progressing to Collapsing Glomerulopathy in Renal Transplant Recipients With and Without COVID-19 Infection.

BACKGROUND: Collapsing glomerulopathy (CGN) secondary to HIV or COVID-19 infection mainly occurs in patients of African American descent due to APOL-1 gene mutations, but CGN is occasionally reported in white patients. CGNs are rarely reported in renal transplant biopsies and their association with idiopathic focal segmental glomerulosclerosis (FSGS) is unclear. METHODS AND RESULTS: Patient #1 was a 48-year-old Caucasian white man who had a renal transplant 8 years ago and was recently diagnosed with COVID-19 infection. Two weeks post infection, his serum creatinine (SCr) increased to 2.01 mg/dL from a baseline of 1.40 mg/dL, and he developed concomitant nephrotic range proteinuria. The first renal transplant biopsy showed FSGS. Four weeks later, his sCr level increased to 2.65 mg/dL with worsening proteinuria, and a second renal transplant biopsy revealed CGN. Patient #2 was a 32-year-old African American man whose native renal biopsy revealed primary FSGS. He received a renal transplant with initial post-transplant sCr level at 1.17 mg/dL. Four months later, his sCr and protein-to-creatinine ratio began to rise. Sequential biopsies revealed that the patient had developed recurrent FSGS, which progressed to show features of CGN. The CGN was further confirmed in his transplant kidney graft at autopsy later. CONCLUSIONS: This is the first case report of CGN in a white renal recipient with COVID-19 infection. The pathologic presentations of FSGS progressing to collapsing FSGS in our 2 renal transplant recipients suggest that FSGS and GGN may share a common pathophysiologic mechanism of podocytopathy.

Resolving primary membranous glomerulopathy (MGN) reveals a dynamically metabolic pathway from sub-epithelium to glomerular basement membranes.

In idiopathic (primary) membranous glomerulopathy (MGN), there is a phenomenon of subepithelial deposits (stages 1 and 2) transitioned to intramembranous deposits, with lucent resolving features (stages 3 and 4). This phenomenon has not been described in other types of immune complex mediated glomerulonephritis with either subendothelial or mesangial deposits. The goal of this study was to evaluate what unique immunostaining pattern could occur in primary MGNs with intramembranous resolving features. PLA2R and IgG4 immunostains were performed in 50 primary MGNs, and 39 secondary MGNs after the clinical history was reviewed. Primary MGNs with resolving features were further evaluated in detail. A total of 84% (42/50) of primary MGN cases had diffuse positive immunostaining for IgG4 in the glomeruli, and most of them were also positive for PLA2R staining. Eight of the remaining primary MGN cases (8/50) with positive PLA2R but negative IgG4 staining in the glomeruli had diffuse resolving features as observed by electron microscopy. All secondary MGNs were stained negatively for both IgG4 and PLA2R except for one case with positive IgG4 staining but negative staining for PLA2R. Our data indicate that IgG4 staining on paraffin tissue is a very reliable screening tool to confirm the presence of primary MGN. Primary MGN with PLA2R+/IgG4- stains were seen in those with intramembranous resolving features. This finding is consistent with the known weak-binding capacity of IgG4 to the glomerular basement membranes. The transitional phenomenon from PLA2R+/IgG4+ subepithelial deposits to PLA2R+/IgG4- intramembranous resolving deposits in primary MGN implies that there may be a continuous metabolic activity from podocyte to glomerular basement membrane.

Role of progenitor cell marker CD133 in supporting diagnosis of collapsing glomerulopathy.

PURPOSE: A previous immunofluorescent study suggests that, in collapsing glomerulopathy, most hyperplastic podocytes that stained positively for a progenitor cell marker CD133 are derived from CD133 + parietal epithelial cells. In pathology practice, not all renal biopsies with collapsing glomerulopathy show the typical morphologic features for this entity, which include florid podocyte hyperplasia, collapsing glomerular capillary loops, and cystic tubular dilation. This study was made to determine if CD133 staining using an immunohistochemical method can be used to confirm hyperplastic podocytes and identify extensive acute tubular injury in collapsing glomerulopathy. METHODS: Twenty-one collapsing glomerulopathy biopsies were stained for CD133 and compared with 15 biopsies with focal segmental glomerulosclerosis, not otherwise specified (FSGS). RESULTS: All patients with collapsing glomerulopathy were of African American descent with prominent renal failure and nephrotic range proteinuria. In contrast, the FSGS group consisted of patients from a variety of ethnic backgrounds with nephrotic range proteinuria but relatively low serum creatinine. The striking finding was that all collapsing glomerulopathy cases showed positive CD133 staining in the clusters of hyperplastic podocytes. There was significantly higher CD133-positive staining rate for hyperplastic podocytes (38%) in the glomeruli of the collapsing glomerulopathy group when compared to small clusters of hyperplastic podocytes in the FSGS group (8%). In addition, when compared to the relatively weak CD133 staining in the proximal tubules of the FSGS group, the proximal tubules of the collapsing glomerulopathy group all showed diffuse and strong CD133 staining as a feature of severe acute tubular injury, which corresponded to the high serum creatinine levels in these patients. CONCLUSION: Our data indicate that the combination of the distinctive mosaic CD133 staining in hyperplastic podocytes and the diffuse tubular CD133 staining is helpful in supporting a diagnosis of collapsing glomerulopathy.

Pathologic Correlation with Renal Dysfunction after Intravitreal Injections of Vascular Endothelial Growth Factor Antagonists.

OBJECTIVE: Vascular endothelial growth factor (VEGF) antagonists have been used for treating metastatic neoplasms. It has also been known that one of its side effects is to cause proteinuria and renal failure in the setting of thrombotic microangiopathy (TMA). The underlying mechanism is likely due to the inhibition of VEGF production in podocytes, resulting in diffuse fusion of foot processes and impaired glomerular endothelial fenestrations, and leading to massive proteinuria and subsequent glomerular endothelium injury. Intravitreal injection of VEGF antagonists (IIVA) has been also used to treat macular degeneration and diabetic retinal neo-vascular proliferation. The majority of patients tolerate the treatment well. However, IIVA can lead to renal dysfunction including proteinuria and gradual renal failure as a rare side effect. The goal of this study was to report two cases related to the nephrotoxicity of IIVA and review the literature associated with this topic. CASE REPORT: The first diabetic patient had elevated serum creatinine at 3.25 mg/dl and proteinuria/creatinine ratio at 6.1 after 48-month treatment of IIVA. The first renal biopsy revealed thrombotic microangiopathy that was correlated with his increased serum creatinine and nephrotic range of proteinuria. The second diabetic patient had increased serum creatinine up to 1.89 mg/dl but low proteinuria. The second biopsy showed acute tubular necrosis that was correlated with his elevated serum creatinine. CONCLUSION: Intravitreal injection of VEGF antagonist can be associated with thrombotic microangiopathy and acute tubular necrosis, leading to renal dysfunction.

Myeloperoxidase immunohistochemical staining can identify glomerular endothelial cell injury in dense deposit disease.

BACKGROUND: Previous studies have demonstrated residual complement-mediated deposits in repeat kidney biopsies of C3 glomerulopathies (C3G) (dense deposit disease (DDD) and C3 glomerulonephritis) following eculizumab treatment, despite some clinical improvement. With residual complement deposition, it is difficult to determine whether there is a reduced complement-mediated endothelial cell injury. We validated that myeloperoxidase (MPO) immunohistochemical staining identified glomerular endothelial cell injury in crescentic glomerulonephritis and C3G. CASE (DIAGNOSIS/TREATMENT): We report that MPO staining in the glomerular endothelium of the post-treatment kidney biopsy was significantly reduced after 3 years of eculizumab treatment and clinical improvement in a 5-year-old boy with initial DDD and secondary crescent formation. CONCLUSION: We find that immunostaining for MPO is a useful method to compare glomerular endothelial injury in C3G following eculizumab treatment. This finding also supports the notion that eculizumab, a C5 blocker, may not mainly block C3 deposits in the glomeruli but significantly blocks final activation of the complement cascade, thus reducing glomerular endothelial cell injury.

Primary Parotid Tumor Thrombosis: Immunohistologic Features and Awareness of Metastatic Potential.

Tumor thrombosis is a poor prognostic feature and an exceptionally rare occurrence in salivary gland malignancies. We present a case of primary parotid myoepithelial carcinoma (MC) with tumor thrombosis in the external jugular vein (EJV). An 82-year-old man presented with a right-sided facial mass. MRI with and without gadolinium demonstrated a mass of the right parotid gland with a filling defect of the right EJV. The patient underwent right parotidectomy and selective neck dissection. Tumor thrombosis was found intraoperatively within the EJV. Final pathology demonstrated a poorly differentiated MC. Adjuvant radiation therapy without concurrent systemic therapy was administered. Three months later, restaging positron emission tomography (PET) with CT revealed numerous bilateral pulmonary nodules with biopsy, demonstrating poorly differentiated MC without locoregional relapse. Given that primary parotid tumor thrombosis is associated with a poor prognosis, the use of early systemic therapy should be investigated.

A Brief History, the Progress in the Variants of Therapies against Metastatic Neoplasms, and the Role of Pathologists.

Chemotherapy originated in the early 1960s. The initial chemotherapeutic agents focused on blocking metabolic pathways and found substantial success in certain types of tumors, but they are generally considered toxic to all normal and tumor cells, and they have significant side effects. As more scientific studies began to identify many new, specific targets and mutations, along with a multitude of growth pathways in tumor cells, new agents targeting cell growth pathways began to emerge in the late 1990s and early 2000s. In 2003, a method called morphoproteomics was developed to evaluate the immunohistochemical protein expressions of target markers in tumors, and it has been considered a pioneering method for guiding targeted therapy. Subsequently, many genomic techniques have been established for identifying specific mutations and tumor markers in order to guide the targeted therapy. More recently, immuno-oncology therapy targeting specific immune markers has been rapidly developed, and the immunohistochemical evaluation of specific immune markers such as PD-L1 demonstrates further expansion of oncologic morphoproteomics. This brief review will focus on the role of pathologists in developing various techniques and guiding targeted therapies during the era of personalized medicine.

Extracellular vesicles mediate cellular interactions in renal diseases-Novel views of intercellular communications in the kidney.

The kidney is a complicated and important internal organ receiving approximately 20% of the cardiac output and mediates numerous pathophysiologic actions. These include selectively filtering macromolecules of the blood, exquisite reclaimation of electrolyctes, urine concentration via an elegant osmotic mechanism, and excretion of an acid load. In addition, the renal tubules carry out secretory functions and produce hormones and cytokines. The kidney receives innervation and hormonal regulation. Therefore, dysfunction of the kidney leads to retention of metabolic waste products, and/or significant proteinuria and hematuria. In the past several decades, the role of extracellular vesicles (EVs) in intercellular communications, and the uptake of EVs by recipient cells through phagocytosis and endocytosis have been elucidated. The new knowledge on EVs expands over the classical mechanisms of cellular interaction, and may change our way of thinking of renal pathophysiology in the subcellular scale. Based on some ultrastructural discoveries in the kidney, this review will focus on the role of EVs in intercellular communications, their internalization by recipient cells, and their relationship to renal pathology.

The clinical features of overlap syndrome (ANCA-associated crescentic glomerulonephritis [AACGN] and immune complex-mediated glomerulonephritis) are similar to those of AACGN alone.

The overlap syndromes of anti-neutrophil cytoplasmic antibodies (ANCA)-associated crescentic glomerulonephritis (AACGN) and variants of immune complex medicated glomerulopathy (ICMGN) have been reported. But very few have compared AACGN alone with the overlap syndromes (AACGN plus ICMGN). The aim of this retrospective study was to make that comparison, following serum creatinine (sCr) to determine whether the two groups (AACGN-only group versus overlap group) would behave differently over time. We identified 14 cases with dual diagnoses of AACGN and various ICMGN in the overlap group. Data were collected and compared with 15 randomly selected AACGN-only cases over the similar period of time. The overlap syndrome represented 0.35% of our overall biopsies (14/4049). All 14 patients were ANCA positive and had crescentic formation. The percentage of crescents in the biopsies ranged from 10 to 78%. ICMGN included the following: membranoproliferative glomerulonephritis, post-infectious glomerulonephritis, membranous glomerulopathies, idiopathic mesangial proliferative glomerulonephritis, lupus nephritis, and IgA nephropathy. With the exception one biopsy revealing lupus nephritis class III, most of the ICMGN were mild. When compared to the AACGN-only group, there were no significant differences in clinical and histologic indices including age, percent of crescents, and sCr (on biopsy days, and over the follow-up periods), although the numbers of follow-up cases were limited over time. Our findings suggest that AACGN was the dominant disease process in the majority of overlap syndromes between AACGN and ICMGN, similar to the clinical processes of AACGN-only disease, therefore, the AACGN in overlap syndrome cases should be the main target for clinical management.