The aim of this work was to perform a comparative analysis of the prevalence and clinical and laboratory features of the course of COVID-19 infection in patients with end-stage chronic kidney disease receiving kidney replacement therapy (KRT). Methods. A retrospective analysis of 73 medical records of patients undergoing KRT and infected COVID-19 between January 1, 2021 and December 31, 2021. The patients were divided into two groups. The first group consisted of 54 hemodialysis (HD) patients, and the second group included 19 peritoneal dialysis (PD) patients. Routine clinical and laboratory characteristics, morbidity, and mortality of COVID-19 depending on KRT modality were analysed. Results. The overall prevalence of COVID-19 was 37.63%. Mortality in this cohort of patients was 19.07%, and mortality associated with COVID-19 was 6.19%. Despite the predominance of COVID-19-associated morbidity in HD patients (46.55% vs. 24.36%, p = 0.05), mortality was not statistically significantly different between the studied groups (26.32% in PD patients vs. 12.96% in HD patients, p = 0.17). HD patients had more severe lung injury as measured by SpO2 (p=0.18) and CT (p=0.003), while PD patients had lower hemoglobin (p=0.001), platelet (p=0.001), total protein (p<0.001), and albumin (p<0.001) levels. A direct correlation was found between the percentage of lung injury according to the CT data and the leukocyte count in both the HD (r = 0.24) and PD (r = 0.56) groups. In addition, an inverse correlation between leukocyte and SpO2 values and between the percentage of lung injury according to the CT data and SpO2 indicators was found in the HD (r = -0.51 and r = -0.66) and PD (r = -0.47 and r = -0.63) groups, respectively. Conclusions. The results of our study are in complete agreement with published data and show the same COVID-19-associated mortality in HD and PD patients, with a statistically significantly higher prevalence of COVID-19 in HD patients. The course of COVID-19 in HD patients is characterized by more severe lung injury compared to PD patients, while PD patients had more pronounced anemia and significantly lower platelet, total protein, and blood albumin concentrations.

Microscopic polyangiitis (MPA) is one of the three clinical phenotypes of vasculitis associated with antineutrophil cytoplasmic antibodies (ANCA). Although MPA is considered a rare form of ANCA-associated vasculitis (AAV), clinical evidence shows that it is fairly common among nephrologists, as it manifests as a systemic, weak-immune vasculitis affecting glomerular capillaries, resulting in necrotizing glomerulonephritis (GN) diagnosed in nearly 100% of MPA patients. The issue of AAV in general, and MPA specifically, has gained significant importance in the context of the ongoing SARS-CoV-2 coronavirus pandemic, as both conditions share common anatomical sites of infection and inflammation. This study presents three new cases of MPA in post-COVID-19 patients. The analysis and presentation encompassed demographic data, patient history regarding comorbidities, details of follow-up care, chronology with COVID-19, and laboratory findings at the time of MPA diagnosis. A comparative analysis of the chronological progression of MPA in the documented clinical cases reveals the polymorphic nature of early-stage clinical manifestations, as well as diverse patterns of disease progression in the advanced stage. Additionally, we provide a brief literature review on diagnostic challenges, pathogenetic mechanisms underlying the relationship between SARS-CoV-2 and AAV, and peculiarities of clinical presentations in early and advanced stages of MPA.