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.

Pregnancy as a susceptible state for thrombotic microangiopathies.

Pregnancy and the postpartum period represent phases of heightened vulnerability to thrombotic microangiopathies (TMAs), as evidenced by distinct patterns of pregnancy-specific TMAs (e.g., preeclampsia, HELLP syndrome), as well as a higher incidence of nonspecific TMAs, such as thrombotic thrombocytopenic purpura or hemolytic uremic syndrome, during pregnancy. Significant strides have been taken in understanding the underlying mechanisms of these disorders in the past 40 years. This progress has involved the identification of pivotal factors contributing to TMAs, such as the complement system, ADAMTS13, and the soluble VEGF receptor Flt1. Regardless of the specific causal factor (which is not generally unique in relation to the usual multifactorial origin of TMAs), the endothelial cell stands as a central player in the pathophysiology of TMAs. Pregnancy has a major impact on the physiology of the endothelium. Besides to the development of placenta and its vascular consequences, pregnancy modifies the characteristics of the women's microvascular endothelium and tends to render it more prone to thrombosis. This review aims to delineate the distinct features of pregnancy-related TMAs and explore the contributing mechanisms that lead to this increased susceptibility, particularly influenced by the "gravid endothelium." Furthermore, we will discuss the potential contribution of histopathological studies in facilitating the etiological diagnosis of pregnancy-related TMAs.

Relevance of inflammatory and complement activation biomarkers profiling in antiphospholipid syndrome patients outside acute thrombosis.

OBJECTIVES: To evaluate whether inflammatory and complement biomarkers are associated with specific characteristics of antiphospholipid syndrome (APS). METHODS: Serum levels of interleukin (IL)-1ß (IL-1ß), IL-6, IL-8, IL-10, tumour necrosis factor (TNF)-α, interferon-α (IFN)-α, IFN-γ, vascular endothelial growth factor (VEGF), intercellular adhesion molecule 1 (ICAM-1), E-selectin, and vascular cell adhesion molecule (VCAM)-1, and plasma levels of soluble C5b-9 (sC5b-9), C3a, C4a, Bb fragment were measured in unselected APS patients. Twenty-five healthy blood donors were included as controls. RESULTS: Between January 2020 and April 2021, 98 APS patients were included outside acute thrombosis (median time from the last APS manifestation: 60 (23;132) months). Levels of IL6, VCAM-1, sC5b-9, C3a, C4a, and Bb were significantly increased in APS patients compared to controls. A cluster analysis allowed to divide patients into two clusters: "inflammatory" (higher levels of IL-6 and VCAM-1) and "complement". In APS, elevated IL-6 was associated with hypertension, diabetes, BMI, and hypertriglyceridaemia. 85% of our APS patients had elevated levels of at least one complement biomarker. Elevated Bb (34%) was associated with aPL positivities, especially with triple aPL positivity (50% vs. 18%, p<0.001). 7/8 patients with history of catastrophic APS had elevated levels of complement biomarkers. CONCLUSIONS: Our findings suggested that APS patients outside acute thrombosis might be divided into two clusters: "inflammatory" and "complement". Elevated IL-6 was associated with cardiovascular risk factors and metabolic parameters, whereas Bb fragments, a marker of alternative pathway complement activation, was strongly associated with aPL profile at highest risk of severe disease.

Hemolysis is associated with altered heparan sulfate of the endothelial glycocalyx and with local complement activation in thrombotic microangiopathies.

The complement system plays a key role in the pathophysiology of kidney thrombotic microangiopathies (TMA), as illustrated by atypical hemolytic uremic syndrome. But complement abnormalities are not the only drivers of TMA lesions. Among other potential pathophysiological actors, we hypothesized that alteration of heparan sulfate (HS) in the endothelial glycocalyx could be important. To evaluate this, we analyzed clinical and histological features of kidney biopsies from a monocentric, retrospective cohort of 72 patients with TMA, particularly for HS integrity and markers of local complement activation. The role of heme (a major product of hemolysis) as an HS-degrading agent in vitro, and the impact of altering endothelial cell (ECs) HS on their ability to locally activate complement were studied. Compared with a positive control, glomerular HS staining was lower in 57 (79%) patients with TMA, moderately reduced in 20 (28%), and strongly reduced in 37 (51%) of these 57 cases. Strongly reduced HS density was significantly associated with both hemolysis at the time of biopsy and local complement activation (C3 and/or C5b-9 deposits). Using primary endothelial cells (HUVECs, Glomerular ECs), we observed decreased HS expression after short-term exposure to heme, and that artificial HS degradation by exposure to heparinase was associated with local complement activation. Further, prolonged exposure to heme modulated expression of several key genes of glycocalyx metabolism involved in coagulation regulation (C5-EPI, HS6ST1, HS3ST1). Thus, our study highlights the impact of hemolysis on the integrity of endothelial HS, both in patients and in endothelial cell models. Hence, acute alteration of HS may be a mechanism of heme-induced complement activation.

The receptor for advanced glycation end products is a sensor for cell-free heme.

Heme's interaction with Toll-like receptor 4 (TLR4) does not fully explain the proinflammatory properties of this hemoglobin-derived molecule during intravascular hemolysis. The receptor for advanced glycation end products (RAGE) shares many features with TLR4 such as common ligands and proinflammatory, prothrombotic, and pro-oxidative signaling pathways, prompting us to study its involvement as a heme sensor. Stable RAGE-heme complexes with micromolar affinity were detected as heme-mediated RAGE oligomerization. The heme-binding site was located in the V domain of RAGE. This interaction was Fe3+ -dependent and competitive with carboxymethyllysine, another RAGE ligand. We confirmed a strong basal gene expression of RAGE in mouse lungs. After intraperitoneal heme injection, pulmonary TNF-α, IL1ß, and tissue factor gene expression levels increased in WT mice but were significantly lower in their RAGE-/- littermates. This may be related to the lower activation of ERK1/2 and Akt observed in the lungs of heme-treated, RAGE-/- mice. Overall, heme binds to RAGE with micromolar affinity and could promote proinflammatory and prothrombotic signaling in vivo, suggesting that this interaction could be implicated in heme-overload conditions.

A simple score to predict early death after kidney transplantation.

BACKGROUND: Few studies have focused on risk stratification for premature death after transplantation. However, stratification of individual risk is an essential step in personalized care. MATERIAL AND METHODS: We have developed a risk score of early post-transplant death (ORLY score) in a prospective multicentre cohort including 942 patients and validated our model in a retrospective independent replication cohort including 874 patients. RESULTS: 60 patients (6.4%) from the prospective cohort died during the first three-year post-transplant. Age, male gender, diabetes, dialysis duration and chronic respiratory failure were associated with early post-transplant death. The multivariable model exhibited good discrimination ability (C-index = 0.78, 95%CI [0.75-0.81]). ORLY score highly predicted early death after transplantation (1.34; 95%CI, 1.22 to 1.48 for each increase of 1 point in score; P < .001). The predictive value of the score in the validation cohort was close to that observed in the experimental cohort (1.41; 95%CI, 1.27 to 1.56 for each increase of 1 point in score; P < .001). Merging the two cohorts, four categories of risk could be individualized: low, 0-5 (n = 522, mean risk, 1%); intermediate, 6-7 (n = 739, mean risk 4.7%); moderate, 8-10 (n = 429, mean risk 10%); and high risk 11-15 (n = 132, mean risk 19%). CONCLUSIONS: The ORLY score discriminates patients with high risk of early death.

Tubulointerstitial damage and interstitial immune cell phenotypes are useful predictors for renal survival and relapse in antineutrophil cytoplasmic antibody-associated vasculitis.

The aims of this study were to determine whether tubulointerstitial damage in the form of interstitial fibrosis/tubular atrophy and total interstitial inflammation predicted progression to end stage renal disease (ESRD) and/or renal relapse (RR) in patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV). One hundred thirteen patients with AAV from six French centers with an index biopsy performed between 2003 and 2013 were included. Histological assessments using the AAV glomerular classification and the kidney allograft Banff classification were performed on pathological review. Biopsy tissues were also investigated by CD3, CD20, CD68, CD163, FOXP3 and RORγt immunohistochemical staining. Competing risks models were calculated. Of the 113 patients, 26 (23.0%) died during follow-up and 29 (25.6%) developed ESRD. Among the 94 patients who achieved remission by the end of induction therapy without developing ESRD, 26 (27.6%) experienced RR. The two independent prognostic factors for ESRD were the estimated glomerular filtration rate at presentation (HR 0.35; 95% CI 0.23-0.51; P < 0.0001) and IF/TA > 25% (HR 2.27; 95% CI 1.18-4.37; P = 0.014). When the distribution of interstitial immune cell phenotypes was included in a second multivariable model, the organization of lymphocytic infiltrates was also an independent predictor of ESRD (HR 2.86; 95% CI 1.35-6.1, P = 0.006). The independent risk factors for RR were a higher CD3/CD20 ratio (HR 1.39; 95% CI 1.05-1.85; P = 0.02) and the presence of RORγt positive cells (HR 2.70; 95% CI 1.11-6.54; P = 0.02). Our results highlight the prognostic value of initial histological evaluations in AAV. Measurements of tubulointerstitial damage and interstitial immune cell phenotype distributions should be considered to improve risk assessments for ESRD and RR.

[Kidney disease care for the elderly]. / Spécificités des néphropathies du sujet âgé.

In our aging population, kidney disease management needs to take into account the frailty of the elderly. Standardized geriatric assessments can be proposed to help clinicians apprehend this dimension in their daily practice. These tools allow to better identify frail patients and offer them more personalized and harmless treatments. This article aims to focus on the kidney diseases commonly observed in elderly patients and analyze their specific nephrogeriatric care modalities. It should be noticed that all known kidney diseases can be also observed in the elderly, most often with a quite similar clinical presentation. This review is thus focused on the diseases most frequently and most specifically observed in elderly patients (except for monoclonal gammopathy associated nephropathies, out of the scope of this work), as well as the peculiarities of old age nephrological care.

Hypercalcemia is common during Pneumocystis pneumonia in kidney transplant recipients.

A few cases of hypercalcemia related to Pneumocystis jirovecii pneumonia (PJP) have previously been described, supposedly associated with an 1α-hydroxylase enzyme-dependent mechanism. The prevalence and significance of hypercalcemia in PJP remain unclear, especially in kidney transplant recipients (KTR) who frequently display hypercalcemia via persisting hyperparathyroidism. We here retrospectively identified all microbiologically-proven PJP in adult KTR from 2005 to 2017 in the Lille University Hospital, and studied the mineral and bone metabolism parameters during the peri-infectious period. Clinical features of PJP-patients were analyzed according to their serum calcium level. Hypercalcemia (12.6 ± 1.6 mg/dl) was observed in 37% (18/49) of PJP-patients and regressed concomitantly to specific anti-infectious treatment in all cases. No other cause of hypercalcemia was identified. In hypercalcemic patients, serum levels of 1,25-dihydroxyvitamin D were high at the time of PJP-diagnosis and decreased after anti-infectious treatment (124 ± 62 versus 28 ± 23 pg/mL, p = 0.006) while PTH serum levels followed an inverse curve (35 ± 34 versus 137 ± 99 pg/mL, p = 0.009), suggesting together a granuloma-mediated mechanism. Febrile dyspnea was less frequent in hypercalcemic PJP-patients compared to non-hypercalcemic (29 versus 67%). In summary, hypercalcemia seems common during PJP in KTR. Unexplained hypercalcemia could thus lead to specific investigations in this particular population, even in the absence of infectious or respiratory symptoms.

Adverse events associated with currently used medical treatments for cystinuria and treatment goals: results from a series of 442 patients in France.

OBJECTIVE: To evaluate medical treatments, in terms of adverse events (AEs) and therapeutic goals, in a large series of patients with cystinuria. PATIENTS AND METHODS: Data from 442 patients with cystinuria were recorded retrospectively. Crystalluria was studied in 89 patients. A mixed-effects logistic regression model was used to estimate how urine pH, specific gravity and cysteine-binding thiols (CBT) correlate with risk of cystine crystalluria. RESULTS: Alkalizing agents and CBT agents were given to 88.8% (n = 381) and 55.3% (n = 238) of patients, respectively. Gastrointestinal AEs were reported in 12.3%, 10.4% and 2.6% of patients treated with potassium bicarbonate, potassium citrate and sodium bicarbonate, respectively (P = 0.008). The percentages of patients who experienced at least one AE with tiopronin (24.6%) and with D-penicillamine (29.5%) were similar (P = 0.45). Increasing urine pH and decreasing urine specific gravity significantly reduced the risk of cystine crystalluria, whereas D-penicillamine and tiopronin treatments did not reduce this risk (odds ratio [OR] 1 for pH ≤6.5; OR 0.52 [95% confidence interval {95% CI} 0.28-0.95] for 7.0 8.0, P <0.001). CONCLUSION: Adverse events were frequent with D-penicillamine and tiopronin. Alkaline hyperdiuresis was well tolerated and reduced cystine crystalluria. Urine specific gravity ≤1.005 and urine pH >7.5, while warning about calcium-phosphate crystallization, should be the goals of medical therapy.

Knockout of receptor for advanced glycation end-products attenuates age-related renal lesions.

Pro-aging effects of endogenous advanced glycation end-products (AGEs) have been reported, and there is increasing interest in the pro-inflammatory and -fibrotic effects of their binding to RAGE (the main AGE receptor). The role of dietary AGEs in aging remains ill-defined, but the predominantly renal accumulation of dietary carboxymethyllysine (CML) suggests the kidneys may be particularly affected. We studied the impact of RAGE invalidation and a CML-enriched diet on renal aging. Two-month-old male, wild-type (WT) and RAGE-/- C57Bl/6 mice were fed a control or a CML-enriched diet (200 µg CML/gfood ) for 18 months. Compared to controls, we observed higher CML levels in the kidneys of both CML WT and CML RAGE-/- mice, with a predominantly tubular localization. The CML-rich diet had no significant impact on the studied renal parameters, whereby only a trend to worsening glomerular sclerosis was detected. Irrespective of diet, RAGE-/- mice were significantly protected against nephrosclerosis lesions (hyalinosis, tubular atrophy, fibrosis and glomerular sclerosis) and renal senile apolipoprotein A-II (ApoA-II) amyloidosis (p < 0.001). A positive linear correlation between sclerosis score and ApoA-II amyloidosis score (r = 0.92) was observed. Compared with old WT mice, old RAGE-/- mice exhibited lower expression of inflammation markers and activation of AKT, and greater expression of Sod2 and SIRT1. Overall, nephrosclerosis lesions and senile amyloidosis were significantly reduced in RAGE-/- mice, indicating a protective effect of RAGE deletion with respect to renal aging. This could be due to reduced inflammation and oxidative stress in RAGE-/- mice, suggesting RAGE is an important receptor in so-called inflamm-aging.

Characterization of Renal Injury and Inflammation in an Experimental Model of Intravascular Hemolysis.

Intravascular erythrocyte destruction, accompanied by the release of pro-oxidative and pro-inflammatory components hemoglobin and heme, is a common event in the pathogenesis of numerous diseases with heterogeneous etiology and clinical features. A frequent adverse effect related to massive hemolysis is the renal injury and inflammation. Nevertheless, it is still unclear whether heme--a danger-associated molecular pattern--and ligand for TLR4 or upstream hemolysis-derived products are responsible for these effects. Well-characterized animal models of hemolysis with kidney impairment are needed to investigate how hemolysis drives kidney injury and to test novel therapeutic strategies. Here, we characterized the pathological processes leading to acute kidney injury and inflammation during massive intravascular hemolysis, using a mouse model of phenylhydrazine (PHZ)-triggered erythrocyte destruction. We observed profound changes in mRNA levels for markers of tubular damage (Kim-1, NGAL) and regeneration (indirect marker of tubular injury, Ki-67), and tissue and vascular inflammation (IL-6, E-selectin, P-selectin, ICAM-1) in kidneys of PHZ-treated mice, associated with ultrastructural signs of tubular injury. Moreover, mass spectrometry revealed presence of markers of tubular damage in urine, including meprin-α, cytoskeletal keratins, α-1-antitrypsin, and α-1-microglobulin. Signs of renal injury and inflammation rapidly resolved and the renal function was preserved, despite major changes in metabolic parameters of PHZ-injected animals. Mechanistically, renal alterations were largely heme-independent, since injection of free heme could not reproduce them, and scavenging heme with hemopexin in PHZ-administered mice could not prevent them. Reduced overall health status of the mice suggested multiorgan involvement. We detected amylasemia and amylasuria, two markers of acute pancreatitis. We also provide detailed characterization of renal manifestations associated with acute intravascular hemolysis, which may be mediated by hemolysis-derived products upstream of heme release. This analysis provides a platform for further investigations of hemolytic diseases and associated renal injury and the evaluation of novel therapeutic strategies that target intravascular hemolysis.

Heme Drives Susceptibility of Glomerular Endothelium to Complement Overactivation Due to Inefficient Upregulation of Heme Oxygenase-1.

Atypical hemolytic uremic syndrome (aHUS) is a severe disease characterized by microvascular endothelial cell (EC) lesions leading to thrombi formation, mechanical hemolysis and organ failure, predominantly renal. Complement system overactivation is a hallmark of aHUS. To investigate this selective susceptibility of the microvascular renal endothelium to complement attack and thrombotic microangiopathic lesions, we compared complement and cyto-protection markers on EC, from different vascular beds, in in vitro and in vivo models as well as in patients. No difference was observed for complement deposits or expression of complement and coagulation regulators between macrovascular and microvascular EC, either at resting state or after inflammatory challenge. After prolonged exposure to hemolysis-derived heme, higher C3 deposits were found on glomerular EC, in vitro and in vivo, compared with other EC in culture and in mice organs (liver, skin, brain, lungs and heart). This could be explained by a reduced complement regulation capacity due to weaker binding of Factor H and inefficient upregulation of thrombomodulin (TM). Microvascular EC also failed to upregulate the cytoprotective heme-degrading enzyme heme-oxygenase 1 (HO-1), normally induced by hemolysis products. Only HUVEC (Human Umbilical Vein EC) developed adaptation to heme, which was lost after inhibition of HO-1 activity. Interestingly, the expression of KLF2 and KLF4-known transcription factors of TM, also described as possible transcription modulators of HO-1- was weaker in micro than macrovascular EC under hemolytic conditions. Our results show that the microvascular EC, and especially glomerular EC, fail to adapt to the stress imposed by hemolysis and acquire a pro-coagulant and complement-activating phenotype. Together, these findings indicate that the vulnerability of glomerular EC to hemolysis is a key factor in aHUS, amplifying complement overactivation and thrombotic microangiopathic lesions.

Glomerulonephritis and granulomatous vasculitis in kidney as a complication of the use of BRAF and MEK inhibitors in the treatment of metastatic melanoma: A case report.

RATIONALE: BRAF and MEK inhibitors have significantly improved the prognosis of metastatic melanoma, by inhibiting both the mitogen-activated protein kinase (MAP-kinase) pathway. They are associated with infrequent adverse kidney events. Most of these are related to the use of BRAF inhibitors and involve interstitial nephritis with acute tubular necrosis. PATIENT CONCERNS: We report a unique case of glomerulonephritis with renal granulomatous vasculitis in a patient diagnosed with metastatic melanoma treated with BRAF and MEK inhibitors. The patient was a 55-year old woman, who presented a melanoma of the right thigh with pulmonary metastasis. Treatment started in November 2015, with Encorafenib and Binimetinib, new BRAF and MEK inhibitors, respectively. Two months after the beginning of the treatment, there was a worsening of her renal function with significant proteinuria. DIAGNOSES: Kidney biopsy showed extracapillary proliferation in the glomeruli with a granulomatous reaction. INTERVENTIONS AND OUTCOMES: Renal function recovered completely after withdrawal of the chemotherapy. LESSONS: All the reported kidney adverse events secondary to BRAF and MEK inhibitors in the literature are related to the use of BRAF inhibitors. Some previous reported mechanistic investigations also provide insight between BRAF inhibitors and podocytes injuries. Therefore, encorafenib most likely is the main responsible of the disease. However, evidence has emerged that inhibition of the MAP kinase pathway could also enhance autoimmunity. Thus, binimetinib may also have played a role and the combination of BRAF and MEK inhibitors may have facilitated this autoimmune kidney disease.

Collapsing glomerulopathy is common in the setting of thrombotic microangiopathy of the native kidney.

Thrombotic microangiopathy (TMA) is a poorly recognized cause of collapsing glomerulopathy. The frequency and significance of collapsing glomerulopathy associated with renal TMA have not been specifically studied in native kidney biopsy specimens. Here we retrospectively documented clinicopathologic features of 53 patients with histologically proven TMA in the native kidney, with special emphasis on changes due to focal segmental glomerulosclerosis (FSGS). Histological TMA was related to hypertensive nephropathy in 21 patients, genetic complement abnormalities in 9, drugs in 7, and to other causes in 16 patients. Almost half (26 patients) presented with arteriolar, 6 with glomerular, and 21 with mixed TMA. Using the Columbia classification system for the 53 patients with histological TMA, 33 had concurrent FSGS lesions with collapsing glomerulopathy the dominant variant in 19 patients (58% of the FSGS cases), not otherwise specified in 9 patients, cellular in 3, and perihilar or tip lesions in 1 patient each. The presence of FSGS was associated with a poor renal prognosis, with no prognostic difference between collapsing glomerulopathy and other FSGS variants. Thus, collapsing glomerulopathy is frequently found in native kidney biopsies with TMA, suggesting that endothelial injury may play an important role in the pathophysiology of FSGS.

FDG PET/CT allowing detection and follow-up of tumor cell transplantation.

After detection of small cell lung cancer in a 67-year-old patient who had donated a kidney 7 months earlier, the graft recipient underwent FDG-PET/CT to determine the presence/absence of tumor cell transmission. It showed abnormal increased uptake of the renal graft, associated with hypermetabolic lymph nodes and hepatic, pulmonary and bone lesions. Emergency graft resection was performed 5 days after PET/CT, permitting immunosuppressive therapy withdrawal. Pathologic examination of the kidney showed parenchymal infiltration by tumor cells compatible with small cell lung cancer. Thereafter, pathologists proved that the recipient's and donor's tumor cells matched using microsatellite markers. FDG-PET/CT was performed in the follow-up and showed progression in the donor despite chemotherapy and radiotherapy. He died a few months later. However, FDG-PET/CT showed a complete metabolic response after only 3 courses of chemotherapy in the recipient.

[Renal malakoplakia: an underestimate cause of renal failure]. / Malacoplakie renale: une cause méconnue d'insuffisance rénale.

Malakoplakia is an inflammatory granulomatous disease induced by defective phagocytic activity of macrophage. Malakoplakia is histologically characterized by the presence of Michaelis-Gutmann bodies in macrophages. Although not uncommon in the genito-urinary tract, isolated malakoplakia of the kidney is rarely found. Its main clinical presentation associates acute renal failure and acute pyelonephritis. The clue for diagnosis of renal malakoplakia is based on renal biopsy showing Michaelis-Gutmann bodies. Establishing the diagnosis of renal malakoplakia is essential as it determines the choice of antibiotics and duration of treatment. Prognosis remains poor, leading frequently to chronic renal failure. In this paper, we report four cases of renal malakoplakia and discuss clinical presentation, biological and pathological features, treatment and prognosis of this disease.