Gasdermin D drives focal crystalline thrombotic microangiopathy by accelerating immunothrombosis and necroinflammation.

ABSTRACT: Thrombotic microangiopathy (TMA) is characterized by immunothrombosis and life-threatening organ failure but the precise underlying mechanism driving its pathogenesis remains elusive. In this study, we hypothesized that gasdermin D (GSDMD), a pore-forming protein that serves as the final downstream effector of the pyroptosis/interleukin-1ß (IL-1ß) pathway, contributes to TMA and its consequences by amplifying neutrophil maturation and subsequent necrosis. Using a murine model of focal crystalline TMA, we found that Gsdmd deficiency ameliorated immunothrombosis, acute tissue injury, and failure. Gsdmd-/- mice exhibited a decrease in mature IL-1ß, as well as in neutrophil maturation, ß2-integrin activation, and recruitment to TMA lesions, in which they formed reduced neutrophil extracellular traps in both arteries and interstitial tissue. The GSDMD inhibitor disulfiram dose-dependently suppressed human neutrophil pyroptosis in response to cholesterol crystals. Experiments with GSDMD-deficient, human-induced, pluripotent stem cell-derived neutrophils confirmed the involvement of GSDMD in neutrophil ß2-integrin activation, maturation, and pyroptosis. Both prophylactic and therapeutic administration of disulfiram protected the mice from focal TMA, acute tissue injury, and failure. Our data identified GSDMD as a key mediator of focal crystalline TMA and its consequences, including ischemic tissue infarction and organ failure. GSDMD could potentially serve as a therapeutic target for the systemic forms of TMA.

Assessment of epidemiology and outcomes of adult patients with kidney-limited thrombotic microangiopathies.

Thrombotic microangiopathies (TMA) are usually associated with hematological features (RH-TMA). The epidemiology of TMA limited to kidneys (RL-TMA) is unclear Therefore, patients with TMA and native kidney biopsies were identified during 2009-2022 in 20 French hospitals and results evaluated. RL-TMA was present in 341/757 (45%) patients and associated with lower creatinine levels (median 184 vs 346 µmol/L) than RH-TMA. RL-TMA resulted from virtually all identified causes, more frequently from anti-VEGF treatment and hematological malignancies but less frequently from shigatoxin-associated hemolytic uremic syndrome (HUS), systemic sclerosis, gemcitabine and bacterial infection, and even less frequently when three or more causes/triggers were combined (RL-TMA: 5%; RH-TMA: 12%). RL-TMA was associated with significantly lower major cardiovascular events (10% vs 20%), kidney replacement therapy (23% vs 43%) and death (12% vs 20%) than RH-TMA during follow-up (median 28 months). Atypical HUS (aHUS) was found in 326 patients (RL-TMA: 43%, RH-TMA: 44%). Among the 69 patients with proven complement-mediated aHUS, eculizumab (anti-C5 therapy) was used in 43 (62%) (RL-TMA: 35%; RH-TMA: 71%). Among the 257 other patients with aHUS, including 51% with RL-TMA, eculizumab was used in 29 but with unclear effects of this treatment. Thus, RL-TMA represents a very high proportion of patients with TMA and results from virtually all known causes of TMA and includes 25% of patients with complement-mediated aHUS. Adverse outcomes of RL-TMA are lower compared to RH-TMA but remain significant. Anti-C5 therapy was rarely used in RL-TMA, even in proven complement-mediated aHUS, and its effects remain to be assessed.

Pegylated Liposomal Doxorubicin Causes Kidney-limited Thrombotic Microangiopathy.

A definite causal link between pegylated liposomal doxorubicin (PLD) and kidney-limited thrombotic microangiopathy (TMA) remains unestablished. Here, we report 2 cases of PLD-induced kidney-limited TMA, 1 in a patient with myxofibrosarcoma and the other in a patient with liposarcoma. The 2 patients received a high cumulative dose of PLD, and both presented with a rise in serum creatinine and proteinuria. Kidney biopsy revealed TMA with chronic mesangiolysis and capillary wall double contouring. Neither patient had concomitant exposure to TMA-causing drugs, such as gemcitabine, anti-vascular endothelial growth factor agents, or mammalian target of rapamycin inhibitors. The work-up for secondary causes of TMA was negative in both patients. The cessation of PLD therapy led to improvement or stabilization in serum creatinine and proteinuria in both patients. These 2 cases provide a clear causal link between PLD and kidney-limited TMA. The high cumulative dose of PLD increases the risk of kidney TMA. Early recognition of PLD-induced kidney TMA can lead to timely cessation of PLD therapy and potentially preserve kidney function.

Outcomes of Early Thrombotic Microangiopathy in Renal Transplantation.

BACKGROUND: Alternate complement dysregulation postrenal transplantation can result in thrombotic microangiopathy (TMA). There is a scarcity of data regarding outcomes based on the timing of TMA post-transplant, coupled with a lack of follow-up biopsy findings post TMA diagnosis. This study aims to assess allograft and patient outcomes in individuals developing early TMA, defined within 4 months post-transplantation, and explore any differences in follow-up surveillance biopsies compared to a non-TMA group. DESIGN: This is a single center retrospective study between January 1, 2002 and October 10, 2019. Patients who developed TMA within 4 months post-transplantation were compared to a propensity matched non-TMA group. RESULTS: Thirty-one patients developed TMA within 4 months of renal transplantation. Index TMA biopsy featured noticeable glomerular, and vascular lesions along with acute tubular injury. Four-month surveillance biopsy showed significant glomerulitis, transplant glomerulopathy and chronic interstitial fibrosis as compared to non-TMA group. However, at 1 year, these differences were no longer significant. There was no significant difference in patient survival (TMA vs. non-TMA, p = 0.083); however, death censored graft survival was significantly lower in the TMA group (p < 0.001). TMA patients had a significantly lower estimated glomerular filtration rate at 4 months and at 1 year as compared to the non-TMA group. CONCLUSION: Early onset TMA post renal transplant leads to decreased renal function and lower graft survival. Early recognition and prompt treatment may help in reducing the adverse outcomes.

Endoscopic manifestation of intestinal transplant-associated microangiopathy after stem cell transplantation.

BACKGROUND: Endoscopic features of intestinal transplant-associated microangiopathy (iTAM) have not been comprehensively investigated. This study aimed to examine the endoscopic characteristics of patients diagnosed with iTAM. METHODS: This retrospective analysis included 14 patients pathologically diagnosed with iTAM after stem cell transplantation for hematolymphoid neoplasms (n = 13) or thalassemia (n = 1). The sex, age at diagnosis, endoscopic features, and prognosis of each patient were assessed. Serological markers for diagnosing transplant-associated thrombotic microangiopathy were also evaluated. RESULTS: The mean age at the time of iTAM diagnosis was 40.2 years. Patients diagnosed based on the pathognomonic pathological changes of iTAM presented with diverse symptoms at the times of endoscopic examinations, including diarrhea (n = 10), abdominal pain (n = 5), nausea (n = 4), appetite loss (n = 2), bloody stools (n = 2), abdominal discomfort (n = 1), and vomiting (n = 1). At the final follow-up, six patients survived, while eight patients succumbed, with a median time of 100.5 days (range: 52-247) post-diagnosis. Endoscopic manifestations included erythematous mucosa (n = 14), erosions (n = 13), ulcers (n = 9), mucosal edema (n = 9), granular mucosa (n = 9), and villous atrophy (n = 4). Erosions and/or ulcers were primarily observed in the colon (10/14, 71%), followed by the ileum (9/13, 69%), stomach (4/10, 40%), cecum (5/14, 36%), duodenum (3/10, 30%), rectum (4/14, 29%), and esophagus (1/10, 10%). Cytomegalovirus infection (n = 4) and graft-versus-host disease (n = 2) coexisted within the gastrointestinal tract. Patients had de novo prolonged or progressive thrombocytopenia (6/14, 43%), decreased hemoglobin concentration (4/14, 29%), reduced serum haptoglobin level (3/14, 21%), and a sudden and persistent increase in lactate dehydrogenase level (2/14, 14%). Peripheral blood samples from 12 patients were evaluated for schistocytes, with none exceeding 4%. CONCLUSIONS: This study provides a comprehensive exploration of the endoscopic characteristics of iTAM. Notably, all patients exhibited erythematous mucosa throughout the gastrointestinal tract, accompanied by prevalent manifestations, such as erosions (93%), ulcers (64%), mucosal edema (64%), granular mucosa (64%), and villous atrophy (29%). Because of the low positivity for serological markers of transplant-associated thrombotic microangiopathy in patients with iTAM, endoscopic evaluation and biopsy of these lesions are crucial, even in the absence of these serological features.

Renal involvement in solid cancers: epidemiological, clinical and histological characteristics study of 154 onconephrology patients.

BACKGROUND: Onconephrology is a growing discipline that aims to improve the management of patients with cancer and kidney disease. If kidney histology is an essential key, the anatomopathological data remain weak although essential to this complex management. METHODS: Patients with active cancer who had a kidney biopsy (KB) between 2014 and 2020 were included, and their clinicobiological and histological data were analyzed retrospectively. RESULTS: Our cohort consisted of 154 patients (83 women) with a mean age of 58 years. One hundred twelve patients presented with proteinuria, 95 with acute kidney injury, and 59 with arterial hypertension. Histologically, interstitial fibrosis was found in 74% of KBs, tubular atrophy in 55.1%, arteriolar hyalinosis in 58.4%, and fibrous endarteritis in 54.4%. Regarding the main acute lesions, thrombotic microangiopathy (TMA) was found in 29.9% of biopsies, acute tubular necrosis (ATN) in 51.3%, and acute interstitial nephritis in 24.8%. The etiological diagnosis most often made was the nephrotoxicity of anticancer drugs (87 patients), followed by a pre-renal (15 patients) and kidney disease unrelated to cancer (13 patients). Sixty-seven patients presented with at least 2 associated diagnoses reflecting the complexity of kidney damage in cancer. Different clusters were found, highlighting that immunotherapy and anti-VEGF were the most commonly involved drugs. CONCLUSIONS: During onconephrology practice, kidney toxicity of treatments is the most common etiology. Several mechanisms can be involved, underscoring the importance of kidney biopsy and the complexity of its management. Chronic histological lesions were very common.

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.

Clinical value of the renal pathologic scoring system in complement-mediated thrombotic microangiopathy.

OBJECTIVES: This study was initiated to establish a renal thrombotic microangiopathy (TMA) scoring system based on clinical needs and investigate its predictive value for patients' long-term outcomes. METHODS: Kidney biopsy-proven Complement-mediated TMA (C-TMA) patients from January 2000 to December 2017 in Peking University First Hospital were retrospectively studied. Both acute and chronic TMA-related lesions, including 15 pathologic indices, were semiquantitatively scored. The interobserver and intraobserver reproducibility and correlation between the pathologic indices and clinical parameters were analyzed. Furthermore, the patients were divided into 2 groups by dialysis use at baseline, and the association of these pathologic indices with their prognostic outcomes was assessed between the two groups. RESULTS: Ninety-two patients with renal biopsy-proven C-TMA were enrolled. All fifteen included pathology indices showed good or moderate interobserver and intraobserver reproducibility and correlated well with several clinical parameters. Several clinicopathological indices were worse in the dialysis group than in the nondialysis group, such as serum creatinine, hemoglobin, platelet count, and estimated glomerular filtration rate. Moreover, morphologic features in the dialysis group presented with more severe vascular lesions. Interstitial fibrosis and chronic tubulointerstitial lesions were related to a trend of high risk of continuous dialysis in the dialysis group. Based on univariate and multivariable Cox regression analysis, more severe glomerular lesions, including glomerular mesangiolysis, glomerular basement membrane double contours and glomerular mesangial proliferation, were identified as risk factors predicting worse prognosis. CONCLUSIONS: Our renal C-TMA semiquantitative scoring system is reliable with good reproducibility and prognostic value in clinical practice, which needs further validation.

[Clinicopathological features and prognosis of kidney injury in patients after hematopoietic stem cell transplantation].

To summarize the clinicopathological features and prognosis of kidney injury after hematopoietic stem cell transplantation (HSCT), to provide basis for preventing its occurrence and development. By using a retrospective cohort study method, we collected the clinical and renal biopsy pathological data of all the patients who hospitalized in the Department of Nephrology of Peking University First Hospital from June 2011 to June 2021 with renal injury after HSCT and underwent renal biopsy, and prognosis was followed up by telephone. The clinical laboratory characteristics, renal pathology and prognosis, and their association were analyzed. The results showed that the most common clinical phenotype was chronic kidney disease (CKD,69.2%, 18/26), in this term 13/18 patients received stem cells from haploidentical donors, and 11/18 patients experienced with extrarenal graft-versus-host disease (GVHD). The most common pathologic phenotype was thrombotic microangiopathy (TMA, 61.5%, 16/26). Renal function returned to baseline level in 6 patients, and the kidney survival at 2 years and 5 years were 95.7% (22/23) and 87.5% (14/16), respectively. In conclusion, the clinical phenotype of renal injury after HSCT were mainly CKD, and the most common pathologic phenotype was TMA, the long-term prognosis was favourable.

Endothelial-specific loss of Krüppel-Like Factor 4 triggers complement-mediated endothelial injury.

Thrombotic microangiopathy (TMA) in the kidney represents the most severe manifestation of kidney microvascular endothelial injury. Despite the source of the inciting event, the diverse clinical forms of kidney TMA share dysregulation of endothelial cell transcripts and complement activation. Here, we show that endothelial-specific knockdown of Krüppel-Like Factor 4 (Klf4)ΔEC, an anti-inflammatory and antithrombotic zinc-finger transcription factor, increases the susceptibility to glomerular endothelial injury and microangiopathy in two genetic murine models that included endothelial nitric oxide synthase knockout mice and aged mice (52 weeks), as well as in a pharmacologic model of TMA using Shiga-toxin 2. In all models, Klf4ΔEC mice exhibit increased pro-thrombotic and pro-inflammatory transcripts, as well as increased complement factors C3 and C5b-9 deposition and histologic features consistent with subacute TMA. Interestingly, complement activation in Klf4ΔEC mice was accompanied by reduced expression of a key KLF4 transcriptional target and membrane bound complement regulatory gene, Cd55. To assess a potential mechanism by which KLF4 might regulate CD55 expression, we performed in silico chromatin immunoprecipitation enrichment analysis of the CD55 promotor and found KLF4 binding sites upstream from the CD55 transcription start site. Using patient-derived kidney biopsy specimens, we found glomerular expression of KLF4 and CD55 was reduced in patients with TMA as compared to control biopsies of the unaffected pole of patient kidneys removed due to kidney cancer. Thus, our data support that endothelial Klf4 is necessary for maintenance of a quiescent glomerular endothelial phenotype and its loss increases susceptibility to complement activation and induction of prothrombotic and pro-inflammatory pathways.

The roles of homocysteinemia and methylmalonic acidemia in kidney injury in atypical hemolytic uremic syndrome caused by cobalamin C deficiency.

BACKGROUND: Cobalamin C (cblC), a vitamin B12 processing protein, plays a crucial role in metabolism for the conversion of homocysteine to methionine and methylmalonyl-CoA to succinyl-CoA. CblC deficiency, an inborn error of cobalamin processing, is a rare cause of atypical hemolytic-uremic syndrome (aHUS) and results in hyperhomocysteinemia and methylmalonic aciduria. Both substances are thought to contribute to thrombotic microangiopathy (TMA) in cblC deficiency patients. However, the roles of homocysteine and methylmalonic acid (MMA) in these patients remain unclear. We want to shed more light on the contributions of homocysteine and MMA levels as contributing factors for thrombotic microangiopathy (TMA)/aHUS by a follow-up of a cblC deficiency patient over 6 years. CASE DIAGNOSIS: A 27-day-old Hispanic female presented with abnormal C3-carnitine on her newborn screen, poor feeding, decreased activity, and oligouria. She was diagnosed with cblC deficiency after laboratory results revealed elevated serum homocysteine, and serum MMA along with genetic testing showing a homozygous pathogenic frameshift variant in MMACHC. The patient developed aHUS and acute kidney injury (AKI), which resolved after appropriate therapy. Over 6 years, she continued to have normal kidney function with no thrombocytopenia despite persistently elevated homocysteine and MMA levels. CONCLUSION: We question the roles of homocysteine and MMA as causative of aHUS/TMA in cblC deficiency as they remained elevated during follow-up but did not result in aHUS/TMA or AKI. Hyperhomocysteinemia and/or MMA caused by other metabolic diseases do not result in aHUS/TMA or AKI. This suggests that other nephrotoxic factors may trigger aHUS/TMA in cblC patients.

A Case of Pulmonary Tumor Thrombotic Microangiopathy: A Rare and Fatal Phenomenon.

Pulmonary tumor thrombotic microangiopathy (PTTM) is a pulmonary hypertensive arteriopathy thought to be caused by activation of the coagulation cascade at the surface of circulating tumor microemboli along with intimal proliferation in small pulmonary arteries in patients with metastatic carcinomas. The subsequent stenosis of the pulmonary vasculature leads to pulmonary hypertension (PH) and, cor pulmonale with eventual respiratory compromise leading to respiratory failure. PTTM is always a nearly fatal disease with most cases diagnosed postmortem. Most cases reported on this condition are from Japan where the incidence of gastric malignancy is relatively higher than other parts of the world. We report a case of a Caucasian man with a classic presentation of PTTM to help make physicians aware of this rare, rapidly progressive and usually fatal phenomenon.

[The role of optical coherence tomography angiography in the assessment of retinal microcirculation in thrombotic microangiopathy associated with malignant arterial hypertension]. / Rol' opticheskoi kogerentnoi tomografii s funktsiei angiografii v otsenke retinal'noi mikrotsirkulyatsii pri tromboticheskoi mikroangiopatii, assotsiirovannoi so zlokachestvennoi arterial'noi gipertenziei.

Optical coherence tomography angiography (OCT-A) allows detailed assessment of the state of local blood flow in various systemic ischemic diseases, which include thrombotic microangiopathy (TMA) associated with malignant arterial hypertension (MAH). PURPOSE: To evaluate retinal microcirculation using OCT-A imaging data in the group of patients with TMA associated with MAH. MATERIAL AND METHODS: The study consisted of a qualitative and quantitative analysis of OCT-A data from 7 patients (14 eyes) with TMA associated with MAH and verified by renal biopsy. The control group included 7 healthy individuals (14 eyes). The following parameters were analyzed: area size of the foveal avascular zone FAZ, mm, vessel density (VD, %) and vessel skeleton density (VSD, %). The indicators were measured separately in the deep and superficial vascular plexuses and divided by localization into: the total density of the entire measured area, central density, density by quadrants (superior, inferior, nasal and temporal). All quadrants were subdivided into inner (corresponding to parafovea) and outer (corresponding to perifovea). RESULTS: Local foci of vascular attenuation of the deep retinal capillary plexus, pathological tortuosity of blood vessels in the deep and superficial retinal capillary plexuses were found in 100% of study group patients. Per-quadrant analysis of OCT-A finding in the macular zone revealed a statistically significant decrease in VD of the deep retinal capillary plexus (p<0.05). A direct correlation was found between glomerular filtration rate and the VD index in the outer inferior (r=0.567; p=0.034) and inner temporal quadrants (r=0.613; p=0.020) of the deep retinal capillary plexus, as well as the level of hemoglobin in blood serum and VD in inner temporal quadrant of the deep vascular plexus (r=0.596; p=0.025). CONCLUSION: Changes revealed with OCT-A are the symptoms of TMA in MAH patients spreading to the retinal microvasculature, mainly at the level of the deep retinal capillary plexus.

[Biomarkers of retinal ischemia in thrombotic microangiopathy associated with malignant arterial hypertension on optical coherence tomography]. / Markery retinal'noi ishemii pri tromboticheskoi mikroangiopatii, assotsiirovannoi so zlokachestvennoi arterial'noi gipertenziei, po dannym opticheskoi kogerentnoi tomografii.

Malignant arterial hypertension is a clinical syndrome characterized by severe diastolic arterial hypertension with signs of ischemic damage to various organs. In some malignant arterial hypertension cases, thrombotic microangiopathy occurs - a rare life-threatening condition characterized by multiple systemic thrombosis of the microvasculature, including in the eyes, which can be clarified by optical scanning of the retina. PURPOSE: To determine markers of retinal ischemia in the eyes with thrombotic microangiopathy associated with malignant arterial hypertension. MATERIAL AND METHODS: The study included 6 patients (12 eyes) with thrombotic microangiopathy associated with malignant arterial hypertension who were examined by optical coherence tomography (OCT) and OCT angiography (OCT-A). All patients suffered from renal dysfunction, which etiology was determined by renal biopsy verifying the presence of renal thrombotic microangiopathy in all cases. RESULTS: According to OCT findings, there were bilateral local foci of thinning of the inner nuclear layer with elevation of the outer plexiform and outer nuclear layers of the retina in 5 out of 6 patients (83%). OCT-A revealed that in most cases (67%), these changes had perivascular localization and corresponded to the areas of attenuation of the deep capillary plexus. A statistically significant thinning of the inner nuclear layer of the retina was found in thrombotic microangiopathy associated with malignant arterial hypertension in comparison with the control group. CONCLUSION: Presence of renal thrombotic microangiopathy confirmed by renal biopsy and the anatomical similarity of the microvasculature of the kidneys and the eyes, give basis to consider the foci of «chronic¼ paracentral acute middle maculopathy detected with OCT in patients with malignant arterial hypertension as biomarkers of thrombotic microangiopathy of the eye.

Cause of death based on systematic post-mortem studies in patients with positive SARS-CoV-2 tissue PCR during the COVID-19 pandemic.

IMPORTANCE: Assessment of the causative association between the COVID-19 and cause of death has been hampered by limited availability of systematically performed autopsies. We aimed to present autopsy-confirmed causes of death in patients who died with COVID-19 and to assess the association between thrombosis and diffuse alveolar damage consistent with COVID-19 (DAD). METHODS: Consecutive forensic (n = 60) and clinical (n = 42) autopsies with positive post-mortem SARS-CoV-2 PCR in lungs (age 73 ± 14 years, 50% men) were included. The cause of death analysis was based on a review of medical records and histological reports. Thrombotic phenomena in lungs were defined as pulmonary thromboembolism (PE), thrombosis in pulmonary artery branches or microangiopathy in capillary vessels. RESULTS: COVID-19 caused or contributed to death in 71% of clinical and 83% of forensic autopsies, in whom significant DAD was observed. Of the patients with COVID-19 as the primary cause of death, only 19% had no thrombotic phenomena in the lungs, as opposed to 38% amongst those with COVID-19 as a contributing cause of death and 54% amongst patients whose death was not related to COVID-19 (p = 0.002). PE was observed in 5 patients. Two patients fulfilled the criteria for lymphocyte myocarditis. CONCLUSIONS: Vast majority of all PCR-positive fatalities, including out-of-hospital deaths, during the SARS-CoV-2 pandemic were related to DAD caused by COVID-19. Pulmonary artery thrombosis and microangiopathy in pulmonary tissue were common and associated with the presence of DAD, whilst venous PE was rarely observed. Histology-confirmed lymphocyte myocarditis was a rare finding.

Synergistic effects of ADAMTS13 deficiency and complement activation in pathogenesis of thrombotic microangiopathy.

Severe deficiency of plasma ADAMTS13 activity is the primary cause of thrombotic thrombocytopenic purpura (TTP) whereas overwhelming activation of complement via an alternative pathway results in atypical hemolytic uremic syndrome (aHUS), the prototypes of thrombotic microangiopathy (TMA). However, clinical and pathogenic distinctions between TTP and aHUS are often quite challenging. Clinical reports have suggested that complement activation may play a role in the development of TTP, which is caused by severe deficiency of plasma ADAMTS13 activity. However, the experimental evidence to support this hypothesis is still lacking. Here, we show that mice with either Adamts13 -/- or a heterozygous mutation of complement factor H (cfh) at amino acid residue of 1206 (ie, cfh W/R ) alone remain asymptomatic despite the presence of occasional microvascular thrombi in various organ tissues. However, mice carrying both Adamts13 -/- and cfh W/R exhibit thrombocytopenia, low haptoglobin, increased fragmentation of erythrocytes in peripheral blood smear, increased plasma levels of lactate dehydrogenase activity, blood urea nitrogen, and creatinine, as well as an increased mortality rate, consistent with the development of TMA. Moreover, mice with a homozygous mutation of cfh (ie, cfh R/R ) with or without Adamts13 -/- developed severe TMA. The mortality rate in mice with Adamts13 -/- cfh R/R was significantly higher than that in mice with cfh R/R alone. Histological and immunohistochemical analyses demonstrated the presence of disseminated platelet-rich thrombi in terminal arterioles and capillaries of major organ tissues in these mice that were either euthanized or died. Together, our results support a synergistic effect of severe ADAMTS13 deficiency and complement activation in pathogenesis of TMA in mice.

Glomerular endothelial activation, C4d deposits and microangiopathy in immunoglobulin A nephropathy.

Immunoglobulin A nephropathy (IgAN) is considered as mesangiopathy since it initiates in the mesangium; however, other glomerular components are involved and the glomerular capillary wall offers the first contact to circulating macromolecular IgA1. Acute and active forms of IgAN are associated with endocapillary hypercellularity and vascular damage of various degrees, in severe cases with microangiopathy (MA) without or with thrombosis [thrombotic microangiopathy (TMA)]. Vascular damage activates complement and coagulation cascades. A defective complement regulation has recently been detected in active and progressive cases of IgAN. C4d deposits in renal biopsies have been found to be an early risk factor. These observations have raised interest in manifestation of MA and TMA in progressive cases of IgAN. MA-TMA lesions have been found in various percentages (2-53%) of patients with IgAN according to patients' selection and pathology definition of TMA. The association with hypertension (HTN) was so strong that it led to the hypothesis that MA/TMA in IgAN was a mere consequence of severe HTN. Old and new clinical and experimental data indicate that in IgAN the interaction of the glomerular capillary wall with immune reactants and complement uncontrolled activation leading to C4b deposits favours the development of MA-TMA, which plays a role in progression and renal function decline. The central role of complement activation is relevant also for the new therapeutic interventions offered by the pharma.

VEGF-VEGFR2 inhibitor-associated hyaline occlusive glomerular microangiopathy: a Japanese single-center experience.

BACKGROUND: Inhibitors of vascular endothelial growth factor (VEGF)-VEGF receptor 2 (VEGFR2) signaling, such as bevacizumab (Bmab), are used for the treatment of various advanced cancers. However, these inhibitors induce renal thrombotic microangiopathy (TMA). Recently, two European cohort studies showed a distinctive histopathological pseudothrombotic pattern different from TMA in Bmab-treated patients. METHODS: We analyzed 9 renal biopsies from proteinuric cancer patients treated with VEGF-VEGFR2 inhibitors in our Japanese cohort. Clinical and laboratory features were also assessed in these patients. RESULTS: All 9 patients had moderate to heavy proteinuria with normal or slightly elevated serum creatinine levels. On light microscopy, a patchy pattern of hemispherical/spherical lesions along glomerular capillary walls was a characteristic finding. On immunofluorescence microscopy, staining for immunoglobulins (IgM dominant) at varying intensities was observed mainly along glomerular capillary walls. Especially, hemispherical/spherical positive staining for immunoglobulins was a characteristic pattern. Immunohistochemical studies showed positive staining for immunoglobulins and negative staining for CD61-positive platelets in capillary hemispherical/spherical lesions and positive VEGF staining in podocytes. On electron microscopy, variably electron-dense material in dilated glomerular capillaries and partial effacement of podocyte foot processes were observed. After the withdrawal of VEGF-VEGFR2 inhibitors, proteinuria improved without any specific treatment in 8 patients. CONCLUSIONS: Histopathological findings in our patients treated with VEGF-VEGFR2 inhibitors were consistent with those observed in the recently described new form of Bmab-associated hyaline occlusive glomerular microangiopathy. This form should be considered in proteinuric cancer patients treated with VEGF-VEGFR2 inhibitors. Discontinuing VEGF-VEGFR2 inhibitors may lead to improvement of glomerular microangiopathy induced by these drugs.

Reversible renal-limited thrombotic microangiopathy due to gemcitabine-dexamethasone-cisplatin therapy: a case report.

BACKGROUND: Gemcitabine and cisplatin are chemotherapeutic agents used for treating multiple cancers, and these agents are sometimes used in combination. Drug-induced thrombotic microangiopathy (TMA) is a rare but potentially fatal complication. It typically presents as a systemic disease with the classical triad of hemolytic anemia, thrombocytopenia, and organ damage. In contrast to systemic TMA, cases of renal-limited TMA, defined as biopsy-proven renal TMA without the classical triad, have been reported with relatively good prognosis. Most cases of renal-limited TMA are associated with calcineurin inhibitors, and cases of drug-induced renal-limited TMA due to gemcitabine-dexamethasone-cisplatin therapy have been rarely reported. CASE PRESENTATION: A 43-year-old woman with lymphoma developed acute kidney injury with marked proteinuria, microhematuria, and abnormal urinary casts after receiving one cycle of gemcitabine-dexamethasone-cisplatin therapy. Although she did not show hemolytic anemia and thrombocytopenia, renal biopsy showed diffuse injury to the glomerular endothelial cells, supporting the diagnosis of renal-limited TMA. Her condition improved only with the cessation of gemcitabine and cisplatin treatment. She received another chemotherapy without gemcitabine and platinum agents, and no recurrence of renal-limited TMA was observed. CONCLUSIONS: Drug-induced TMA occurs early after gemcitabine and cisplatin use in renal-limited form and is reversible when detected and managed in a timely manner. Urinalysis, which is simple and inexpensive and can be easily performed, is a beneficial screening tool for early-onset drug-induced TMA among patients who receive gemcitabine-dexamethasone-cisplatin therapy.

A 57-year-old man with rapidly progressive pulmonary hypertension.

Pulmonary Tumor Thrombotic Microangiopathy (PTTM) is a rare condition associated with neoplastic disorders, predominantly gastric cancer, leading to pre-capillary Pulmonary Hypertension (PH). The pathologic mechanism involved is a fibrocellular intimal proliferation of small pulmonary vessels sustained by nests of carcinomatous cells lodged in pulmonary vasculature. Clinical presentation is nonspecific, including progressive dyspnea and dry cough. Diagnosis of PTTM is extremely challenging ante-mortem and prognosis is poor. Here we describe the case of a middle-aged man, without known previous cancer history. The clinical course was rapidly unfavorable, with progressive dyspnea and PH associated with hemodynamic instability, eventually culminating in patient's death. PTTM diagnosis was made post-mortem. PTTM should be considered in any patient presenting with unexplained PH, especially if it is rapidly progressive, poorly responsive to standard approaches or there is suspected history of malignancy. A prompt diagnosis of PTTM could help in bringing light into this still under-recognized condition.