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.

Clinical Presentation, Pathological Spectrum, and Outcomes of Alcoholic Cirrhosis-Related Immunoglobulin A Nephropathy

Introduction

Immunoglobulin A nephropathy (IgAN) associated with cirrhosis is frequent but often overlooked because it is largely considered silent. Until now, little has been known about their presentation and outcomes.

Methods

We conducted a retrospective multicenter study on patients with kidney biopsy-proven cirrhosis-related IgAN (cirrhosis-IgAN), diagnosed between 2009 and 2022. We mixed them up with 83 primary IgAN (pIgAN) diagnosed during the same period, using a partitioning clustering approach, to determine common clinicopathological profiles.

Results

All the 46 patients with cirrhosis-IgAN had an excessive alcoholic consumption. Clinical presentation was severe with acute kidney injury (AKI) in 79%; alternative causes of AKI was found in 62% of cases. Three clinicopathological clusters were identified as follows: the first one represented chronic involvement, the second one could be assimilated to mild disease, and the third one corresponded to a membranoproliferative glomerulonephritis (MPGN) pattern and was associated with heavy proteinuria and intrinsic AKI (without alternative causes). Whereas the first 2 clusters were equally distributed between pIgAN and cirrhosis-IgAN, the third was more frequent in patients with cirrhosis. The cumulative mortality rate in cirrhosis-IgAN was 26% and 46% at 1-year and 3-years, respectively. Steroid exposure and moderate or severe AKI were associated with higher mortality and steroid exposure was associated with the occurrence of severe infection.

Conclusion

Our results suggest that high AKI incidence is related to extrinsic causes in most cases but can also be driven by IgA-dominant MPGN in a subset of patients. Steroid use was associated with infectious disease and mortality. Further studies are needed to clarify the role of immunosuppressive treatment in cirrhosis-IgAN patients.

Nephrosclerosis in young patients with malignant hypertension

BACKGROUND

Nephrosclerosis is one of the histopathological consequences of severe or malignant hypertension (MH), some of the pathophysiology of which has been extrapolated from essential polygenetic arterial hypertension. Despite our recent description of unsuspected ciliopathies with MH, causes of MH in young patients with severe renal impairment are poorly understood.

METHODS

To refine and better describe the MH phenotype, we studied clinical and prognostic factors in young patients receiving a kidney biopsy following their first episode of MH. Patients were identified retrospectively and prospectively from eight centres over a 35-year period (1985-2020). Keywords were used to retrospectively enrol patients irrespective of lesions found on renal biopsy.

RESULTS

A total of 114 patients were included, 77 (67%) of whom were men, average age 34 years, 35% Caucasian and 34% African origin. An isolated clinical diagnosis of severe nephrosclerosis was suggested in only 52% of cases, with 24% primary glomerulopathies. Only 7% of patients had normal renal function at diagnosis, 25% required emergency dialysis and 21% were eventually transplanted. Mortality was 1% at the last follow-up. Independent prognostic factors significantly associated with renal prognosis (6-month dialysis) and predictive of end-stage renal disease were serum creatinine on admission {odds ratio [OR] 1.56 [95% confidence interval (CI) 1.34-1.96], P < .001} and renal fibrosis >30% [OR 10.70 (95% CI 1.53-112.03), P = .03]. Astonishingly, the presence of any thrombotic microangiopathy lesion on renal biopsy was an independent, protective factor [OR 0.14 (95% CI 0.02-0.60), P = .01]. The histopathological hallmark of nephrosclerosis was found alone in only 52% of study patients, regardless of ethnicity.

CONCLUSIONS

This suggests that kidney biopsy might be beneficial in young patients with MH.

COVID-19-Related Collapsing Glomerulopathy in a Kidney Transplant Recipient

We report a case of a kidney transplant recipient who presented with acute kidney injury and nephrotic-range proteinuria in a context of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Kidney biopsy revealed collapsing glomerulopathy. Droplet-based digital polymerase chain reaction did not detect the presence of SARS-CoV-2 RNA in the biopsy fragment, and the virus was barely detectable in plasma at the time of the biopsy. SARS-CoV-2 RNAemia peaked several days later, followed by a seroconversion despite the absence of circulating CD19-positive lymphocytes at admission due to rituximab-based treatment of antibody-mediated rejection 3 months earlier. Genotyping for the 2 risk alleles of the apolipoprotein L1 (APOL1) gene revealed that the donor carried the low-risk G0/G2 genotype. This case illustrates that coronavirus disease 2019 infection may promote a collapsing glomerulopathy in kidney allografts with a low-risk APOL1 genotype in the absence of detectable SARS-CoV-2 RNA in the kidney and that podocyte injury may precede SARS-CoV-2 RNAemia.