To investigate the histopathological characteristics of patients with lupus nephritis in the 2018 revised International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification and assess the prognostic factors. Methods: This study enrolled 92 patients with lupus nephritis, who had conventional treatment and renal biopsy. Each renal tissue was evaluated according to 2018 ISN/RPS classification, and quantified apoptotic regulator protein, the B-cell lymphoma-2 protein (Bcl-2), expressions in selected lymphocyte subsets were measured using novel computational approaches using multicolor confocal images. Histopathological characteristics and prognostic factors of end-stage renal disease (ESRD) and chronic kidney disease (CKD) were compared. Follow-up data were obtained, and survival analysis was conducted. Results: During follow-up period (average: 74.3 months), 16 and 18 patients progressed ESRD and CKD, respectively. Multivariable analysis of age, sex, disease activity and pathological features in ISN/RPS demonstrated the extent of interstitial inflammation (grade 0~3) was significantly associated with both ESRD and CKD. When interstitial inflammation was divided into mild (grade 0, 1) and severe (grade 2, 3), Cox regression analysis showed that patients with severe interstitial inflammation were significantly increased risk of both ESRD and CKD (hazard ratio: 4.67 and 3.8, respectively). Bcl-2 expression in CD4+ and CD20 cells was significantly higher in the severe interstitial inflammation group compared to in mild interstitial inflammation patients (p=0.006 and 0.010, respectively). Conclusion:The extent of interstitial inflammation can predict clinical renal outcomes. Significantly elevated Bcl-2 expression in both CD4+ and CD20 cells was found in severe interstitial inflammation compared with mild interstitial inflammation.

Thrombotic microangiopathy (TMA) refers to a condition caused by microvascular injury that includes thrombosis, hemolytic anemia, and thrombocytopenia. There are two classic TMAs, hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura, as well as an atypical HUS (aHUS). aHUS includes a broad spectrum of disorders with diverse etiologies and shares clinical manifestations with classic TMA; however, it frequently lacks typical clinical and laboratory findings. These traits can confuse clinicians and pathologists in terms of renal pathologic diagnosis, especially in cases where TMA is associated with other glomerulopathies or hypertensive renal disease. In this review, new paradigms for classifying TMA and the diversity of histopathologic changes including associated renal diseases are discussed. Renal biopsy is an important and useful diagnostic tool for diagnosing TMA and identifying TMA changes in other renal diseases, including hypertension. Adopting the term "TMA features" for TMA-like changes in glomerulus or artery/ arteriole in addition to the pathological diagnosis of glomerulopathy would be informative to clinicians for a prompt diagnosis and treatment of aHUS.

As the global coronavirus disease 2019 (COVID-19) pandemic continues to sweep across the globe, reports of kidney involvement in adult patients infected with COVID-19 have been documented, and recently, cases in the pediatric population have also been reported. This report highlights the case of an 11-year-old boy who developed acute kidney injury presenting as gross hematuria, proteinuria, and hypertension immediately after a COVID-19 infection. A renal biopsy allowed us to diagnose the patient with post-COVID-19 infection-associated de novo crescentic immune-mediated glomerulonephritis. Oral prednisolone and cyclophosphamide treatments were initiated after methylprednisolone pulse therapy administration. Currently, the patient is receiving medical treatment for five weeks, and his renal function is gradually recovering. Previous studies have suggested that, although quite rare, a variety of kidney complications can occur after COVID-19 infection or vaccination, and it is recommended to monitor renal function through evaluation. Herein, we report a pediatric case of post-COVID-19 infection-associated de novo crescentic immune-mediated glomerulonephritis consistent with rapidly progressive glomerulonephritis.

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