COVID-19 and idiopathic nephrotic syndrome in children: systematic review of the literature and recommendations from a highly affected area

Impact of COVID-19 on Pediatric Inflammatory Bowel Diseases-From Expectations to Reality

Viral infections have always been considered a threat to global health, with numerous outbreaks across time. Despite the relative recent experience with coronavirus-associated diseases such as severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), severe acute respiratory syndrome-2's (SARS-CoV-2) continuous evolution displays a different behavior. With a tropism for both respiratory and digestive mucosa, coronavirus disease 2019 (COVID-19) and inflammatory bowel disease (IBD) seem to share a particular common background. Current literature offers evidence that viral alteration of the immune system, inflammatory intestinal tissue damage, increased intestinal permeability, incomplete viral clearance with viral antigen persistence, and intestinal dysbiosis, might explain SARS-CoV-2-IBD relationship in terms of etiopathogenesis and evolution. The hyperinflammatory state that both entities have in common explains the lack of success of current IBD therapy, raising the need for new personalized therapeutic options, with better outcomes for IBD and COVID-19 as well. This review aims to summarize the current available data on pediatric IBD evolution, management, and outcomes in the post-COVID period, with an emphasis on the particular aspects of the SARS-CoV-2-IBD relationship in children.

Managing acute COVID-19 in immunocompromised pediatric patients

INTRODUCTION

SARS-CoV-2 infection is a potentially life-threatening infection in immunocompromised pediatric patients, and its management has rapidly evolved during the pandemic. To control SARS-CoV-2 infection over time, the scenario changed for the better with the introduction of specific treatments such as antiviral drugs, vaccines, and monoclonal antibodies, together with drugs blocking the inflammatory cytokine cascade and improvements in supportive care.

AREAS COVERED

This paper discusses the therapeutic strategies to apply for patients affected by COVID-19 in the pediatric population, with a focus on the immunocompromised patients.

EXPERT OPINION

Treatment in pediatric patients retraces the therapies investigated and approved in adults and must be calibrated on the basis of the severity of the infection (anti-spike monoclonal antibody, antivirals, anti-inflammatory drugs, and immunomodulators). Transmission prevention policies and vaccination reduce the risk of infection, while early intervention in the immunocompromised patients at high-risk of progression to severe-critical COVID-19 may reduce the period of viral shedding and the need for hospitalization, intensive care admission, and death. In hemato-oncological patients, the delayed treatment of SARS-CoV-2 infection or COVID-19 disease represents a frequent complication and its impact on the patient outcome remains a matter of research for the next few years.

Acute kidney injury in children with moderate-severe COVID-19 and multisystem inflammatory syndrome in children: a referral center experience

BACKGROUND

Data on the characteristics of acute kidney injury (AKI) in pediatric COVID-19 and MIS-C are limited. We aimed to define the frequency, associated factors and early outcome of AKI in moderate, severe or critical COVID-19 and MIS-C; and to present a tertiary referral center experience from Türkiye.

METHODS

Hospitalized patients ≤ 18 years of age with confirmed COVID-19 or MIS-C at İhsan Doğramacı Children's Hospital, Hacettepe University, between March 2020-December 2021 were enrolled. The characteristics of AKI in the COVID-19 group were investigated in moderate, severe and critically ill patients; patients with mild COVID-19 were excluded.

RESULTS

The median (Q1-Q3) age in the COVID-19 (n = 66) and MIS-C (n = 111) groups was 10.7 years (3.9-15.2) and 8.7 years (4.5-12.7), respectively. The frequency of AKI was 22.7% (15/66) in COVID-19 and 15.3% (17/111) in MIS-C; all MIS-C patients with AKI and 73.3% (11/15) of COVID-19 patients with AKI had AKI at the time of admission. Multivariate analyses revealed need for vasoactive/inotropic agents [Odds ratio (OR) 19.233, p = 0.002] and presence of vomiting and/or diarrhea (OR 4.465, p = 0.036) as independent risk factors of AKI in COVID-19 patients; and need for vasoactive/inotropic agents (OR 22.542, p = 0.020), procalcitonin and ferritin levels as independent risk factors of AKI in the MIS-C group. Age was correlated with lymphocyte count (r = -0.513, p < 0.001) and troponin level (r = 0.518, p < 0.001) in MIS-C patients. Length of hospital stay was significantly longer in both groups with AKI, compared to those without AKI. Mortality was 9.1% in the COVID-19 group; and was associated with AKI (p = 0.021). There was no mortality in MIS-C patients. AKI recovery at discharge was 63.6% in COVID-19 survivors and 100% in MIS-C patients.

CONCLUSIONS

Independent risk factors for AKI were need for vasoactive/inotropic agents and vomiting/diarrhea in moderate, severe or critical COVID-19 patients; and need for vasoactive/inotropic agents and severe inflammation in MIS-C patients. Our findings suggest that inflammation and cardiac dysfunction are associated with AKI in MIS-C patients; and the association with age in this group merits further studies in larger groups. Early outcome is favorable; long-term follow-up for kidney functions is needed.

Incidence of idiopathic nephrotic syndrome during the Covid-19 pandemic in the Paris area (France) and in the Netherlands

BACKGROUND

The aetiology of idiopathic nephrotic syndrome (INS) remains partially unknown. Viral infections have been associated with INS onset. Since we observed fewer first onset INS cases during the Covid-19 pandemic, we hypothesised that lower INS incidence was the result of lockdown measures. Therefore, the aim of this study was to evaluate the incidence of childhood INS before and during the COVID-19 pandemic in two independent European INS cohorts.

METHODS

Children with new INS in the Netherlands (2018-2021) and Paris area (2018-2021) were included. We estimated incidences using census data for each region. Incidences were compared using two proportion Z-tests.

RESULTS

A total of 128 and 324 cases of first onset INS were reported in the Netherlands and Paris area, respectively, corresponding to an annual incidence of 1.21 and 2.58 per 100,000 children/year. Boys and young children (< 7 years) were more frequently affected. Incidence before and during the pandemic did not differ. When schools were closed, incidence was lower in both regions: 0.53 vs. 1.31 (p = 0.017) in the Netherlands and 0.94 vs. 2.63 (p = 0.049) in the Paris area. During peaks of hospital admissions for Covid-19, no cases were reported in the Netherlands or Paris area.

CONCLUSIONS

Incidence of INS before and during the Covid-19 pandemic was not different, but when schools were closed during lockdown, incidence was significantly lower. Interestingly, incidences of other respiratory viral infections were also reduced as was air pollution. Together, these results argue for a link between INS onset and viral infections and/or environmental factors. A higher resolution version of the Graphical abstract is available as Supplementary information.

Delayed diagnosis and exacerbation of hyperlipidemia in idiopathic nephrotic syndrome in children during the COVID-19 pandemic

BACKGROUND

During the coronavirus disease-2019 (COVID-19) pandemic, there was a lack of access to outpatient facilities for other diseases. Conversely, few studies have reported changes in clinical features of idiopathic nephrotic syndrome (INS) in children before and after the COVID-19 pandemic.

METHODS

Thirty-two children with primary INS, who were admitted to four Showa University-affiliated hospitals between January 2017 and December 2022, were enrolled in this retrospective study. Children were divided according to the onset of INS into a post-COVID-19 group (onset in 2020-2022, n = 25) and a pre-COVID-19 group (onset in 2017-2019, n = 32). We compared the clinical characteristics and features of initial INS between two groups.

RESULTS

In the post-COVID-19 group, these patients had interval between noticing symptoms of INS, such as edema and INS diagnosis was significantly longer (7 days versus 3.5 days; p = 0.0047), and had significantly raised serum LDL cholesterol levels at the time of INS diagnosis than in the pre-COVID-19 group (314 mg/dL versus 260 mg/dL; p = 0.028). Likewise, steroid-resistant nephrotic syndrome was significantly more common in the post-COVID-19 group [32% (n = 8) versus 6% (n = 2); p = 0.016]. A correlation analysis revealed a moderate positive correlation between the interval from symptom to diagnosis and LDL cholesterol (r = 0.460015, p = 0.0003).

CONCLUSIONS

Children with INS after the COVID-19 pandemic showed a longer time between noticing symptoms of INS and diagnosis, increased serum LDL cholesterol and more steroid resistance than before the pandemic.

Nephrotic syndrome: pathophysiology and consequences

In patients with kidney disease, nephrotic syndrome can lead to several complications including progressive kidney dysfunction. Proteinuria may lead to the formation of cellular or fibrous crescents with reciprocal development of rapidly progressive glomerulonephritis or focal glomerulosclerosis. Proteinuria may also cause overload and dysfunction of tubular epithelial cells, eventually resulting in tubular atrophy and interstitial fibrosis. Hypoalbuminemia is usually associated with increased risk of mortality and kidney dysfunction. Dyslipidemia may increase the risk of atherosclerotic complications, cause podocyte dysfunction and contribute to vascular thrombosis. Urinary loss of anticoagulants and overproduction of coagulation factors may facilitate a hypercoagulable state. Edema, hypogammaglobulinemia, loss of complement factors, and immunosuppressive therapy can favor infection. Treatment of these complications may reduce their impact on the severity of NS. Nephrotic syndrome is a kidney disorder that can worsen the quality of life and increase the risk of kidney disease progression.

Kidney complications associated with COVID-19 infection and vaccination in children and adolescents: a brief review

Coronavirus disease 2019 (COVID-19) has spread considerably across the globe, affecting numerous children and adolescents besides adults. Despite its relatively lower incidence rates in children and adolescents than in adults, some infected children and adolescents exhibit a severe postinflammatory response known as multisystem inflammatory syndrome in children, followed by acute kidney injury, a common complication. Meanwhile, few reports have been available regarding kidney complications such as idiopathic nephrotic syndrome and other glomerulopathies associated with COVID-19 infection and vaccination in children and adolescents. However, the morbidity and mortality of these complications are not exceptionally high; more importantly, causality has yet to be clearly established. Finally, vaccine hesitancy in these age groups should be addressed, considering the strong evidence of COVID-19 vaccine safety and efficacy.

Kidney involvement in children during the SARS-CoV-2 Omicron variant pandemic

BACKGROUND

As the coronavirus disease-2019 (COVID-19) pandemic continues, driven by the Omicron variant, infection rates in children have recently rapidly surged compared with previous years. We aimed to investigate the presentation of kidney involvement in children after Omicron variant severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection.

METHODS

We retrospectively reviewed the medical records of pediatric patients who presented with kidney disease with a temporal relationship with COVID-19 between January and August 2022 in a single tertiary center in Korea.

RESULTS

Fifteen children presented with kidney involvement after Omicron variant infection, with a median age of 10.6 (6.8-18.3) years. None of the patients exhibited severe respiratory symptoms apart from cough and sore throat. The median time from infection to renal symptom onset was 3 (0-49) days. Among 10 patients with underlying kidney disease, six had previously been diagnosed with nephrotic syndrome (NS) that relapsed after COVID-19 infection, two with immunoglobulin A nephropathy (IgAN) experienced transient gross hematuria (GHU) with or without acute kidney injury (AKI), and two with kidney transplantation presented with AKI. Of the five patients without underlying kidney disease, one patient had NS, and the other four patients had GHU and proteinuria (PU), of whom one was eventually diagnosed with Henoch Shönlein Purpura nephritis (HSPN), and one with rhabdomyolysis. The seven patients with NS (1 new-onset, 6 relapsed) had uneventful remission with corticosteroid therapy. Apart from one patient with new-onset HSPN, GHU and PU resolved spontaneously in all affected patients, and AKI also resolved with supportive care.

CONCLUSIONS

Kidney involvement subsequent to Omicron variant COVID-19 exhibited various, but mostly mild manifestations in children.

Vaccines and nephrotic syndrome: efficacy and safety

Vaccines represent the most important medical evolution in the last two centuries allowing prevention and formally eradication of a wide number of infectious diseases. Safety and effectiveness are main issues that still require an open discussion. A few clinical reports described a critical temporal relationship between vaccination and acute nephrotic syndrome, indirectly suggesting an association. For this review, the literature was reviewed to identify articles reporting associations of nephrotic syndrome with vaccines against a vast array of infectious diseases (including bacteria, virus and Sars-Cov-2). As specific aims, we evaluated effectiveness and safety in terms of occurrence of either "de novo" nephrotic syndrome in health subjects or "relapse" in those already affected by the disease. In total, 377 articles were found; 166 duplicates and 71 non-full text, animal studies or non-English language were removed. After excluding another 50 articles not containing relevant data on generic side effects or on relapses or new onset nephrotic syndrome, 90 articles met the search criteria. Overall, studies reported the effect of vaccines in 1015 patients, plus 4 nationwide epidemiologic investigations. Limited experience on vaccination of NS patients with measles, mumps, and rubella live attenuated vaccines does not allow any definitive conclusion on their safeness. VZV has been administered more frequently without side effects. Vaccines utilizing virus inactivated, recombinant, and toxoid can be utilized without risks in NS. Vaccines for influenza reduce the risk of infections during the pandemic and are associated with reduced risk of relapse of NS typically induced by the infection. Vaccines for SARS-CoV-2 (all kinds) offer a concrete approach to reduce the pandemic. "De novo" NS or recurrence are very rare and respond to common therapies.

The challenges of the pandemic and the vaccination against covid-19 in pediatric patients with kidney disease

The covid-19 vaccine confers direct protection and reduces transmission rates of the virus and new variants. Vaccines from Pfizer/BioNTech and CoronaVac have been cleared for children in Brazil. They are safe, effective, and immunogenic. There are no known complications associated with the use of steroids or vaccines in pediatric patients with covid-19 and nephrotic syndrome. With or without immunosuppression, these patients are not at increased risk of severe covid-19, and steroids are safe for them. A milder form of covid-19 occurs in patients with chronic kidney disease without the need for hospitalization. The vaccine response may be reduced and/or the duration of antibodies after vaccination may be shorter than in the general population. However, considering risk of exposure, vaccination against covid-19 is recommended. It is believed that patients with hemolytic-uremic syndrome are at higher risk of severe covid-19. Vaccination is recommended, although specific data on the safety and efficacy of the covid-19 vaccine are limited. There is agreement that the benefits of induced immunity outweigh the risks of immunization. Vaccination against covid-19 is recommended for children and adolescents needing kidney transplantation or who have undergone transplantation. These patients present decreased immune response after vaccination, but immunization is recommended because the benefits outweigh the risks of vaccination. Current recommendations in Brazil stipulate the use of the messenger RNA vaccine. This paper aims to provide pediatric nephrologists with the latest knowledge about vaccination against covid-19 for children with kidney disease.

Relapse rate in children with nephrotic syndrome during the SARS-CoV-2 pandemic

BACKGROUND

Viral upper respiratory tract infections trigger nephrotic syndrome relapses. Few data exist on the impact of the SARS-CoV-2 pandemic on the risk of relapse in children with idiopathic nephrotic syndrome (INS).

METHODS

In a Belgian and Italian cohort of children with INS, we performed a retrospective analysis on the number and duration of relapses observed in 3 different periods in 2020: first COVID period, February 15-May 31; second COVID period, June 1-September 14; third COVID period, September 15-December 31. Relapse rates were compared to those of the previous 5 years (PRECOVID period). For the years 2019 and 2020, all causes and INS relapse-related hospitalizations were recorded. Hospitalizations and deaths due to SARS-CoV-2 infection were also recorded. In the Belgian cohort, SARS-CoV-2 serologies were performed.

RESULTS

A total of 218 patients were enrolled, and 29 (13.3%) were diagnosed with new-onset INS during the COVID period. Relapse rates per 1000 person-days were as follows: 3.2 in the PRECOVID period, 2.7 in the first COVID period, 3.3 in the second COVID period, and 3.0 in the third COVID period. The incidence rate ratio for the total COVID period was 0.9 (95%CI 0.76 to 1.06; P = 0.21) as compared to the PRECOVID period. During 2020, both the proportion of patients hospitalized for recurrence (14.2% vs. 7.6% in 2019; P = 0.03) and the rate of hospitalization for recurrence (IRR 1.97 (95%CI 1.35 to 2.88); P = 0.013) were higher compared to 2019. In December 2020, anti-SARS-CoV-2 antibodies were detected in 31% of the Belgian cohort. Patients with positive and negative SARS-CoV-2 serology did not differ significantly in relapse rate (2.4 versus 4.2 per 1000 person-days). The number of new INS cases remained similar between 2020, 2019, and 2018.

CONCLUSION

The first year of the SARS-CoV-2 pandemic did not significantly affect the relapse rate in children with INS. No serious infections were reported in this population of immunosuppressed patients. A higher resolution version of the Graphical abstract is available as Supplementary information.

Epidemiology, severity, and risk of SARS-CoV-2-related relapse in children and young adults affected by idiopathic nephrotic syndrome: a retrospective observational cohort study

BACKGROUND

Children with underlying kidney diseases display a mild course of SARS-CoV-2 infection, but they only accounted for a minority of cases until the spread of the Omicron variant. Nonetheless, idiopathic nephrotic syndrome (INS) has been advocated as a predictor of worse outcome.

METHODS

We investigated the spread, severity, and risk of relapse related to SARS-CoV-2 infection among children with INS. The incidence and characteristics of SARS-CoV-2 infections, immunosuppression, and vaccination status were retrospectively collected from the beginning of the pandemic to May 31, 2022.

RESULTS

We enrolled 176 patients (73 females, median age 10.22 years); 28 had a steroid-resistant disease, and 108 (61.4%) were on immunosuppressive therapy. Sixty-one (34.7%) patients reported a SARS-CoV-2 infection, with incidence peaking between December 2021 and January 2022. No hospitalization or deaths were reported, and symptoms were absent or mild. The rate of SARS-CoV-2 infection was similar in children with and without immunosuppression (33.8% vs 35.2%; p = 0.85). None of the 38 immunosuppressed patients discontinued the therapy, but they had a longer time to negativization (13.31 vs. 10.04 days; p = 0.03). Proteinuria was detected in 7 patients, but only one had a relapse requiring steroid therapy, with prompt remission and a mild course.

CONCLUSIONS

After the spread of the Omicron variant, the rate of SARS-CoV-2 infection in children with INS was much higher than previously reported. In this large cohort, symptoms were mild, even in immunosuppressed patients and those with proteinuria. During the infection, transient proteinuria was common with a low rate of relapses. A higher resolution version of the Graphical abstract is available as Supplementary information.

IPNA clinical practice recommendations for the diagnosis and management of children with steroid-sensitive nephrotic syndrome

Idiopathic nephrotic syndrome is the most frequent pediatric glomerular disease, affecting from 1.15 to 16.9 per 100,000 children per year globally. It is characterized by massive proteinuria, hypoalbuminemia, and/or concomitant edema. Approximately 85-90% of patients attain complete remission of proteinuria within 4-6 weeks of treatment with glucocorticoids, and therefore, have steroid-sensitive nephrotic syndrome (SSNS). Among those patients who are steroid sensitive, 70-80% will have at least one relapse during follow-up, and up to 50% of these patients will experience frequent relapses or become dependent on glucocorticoids to maintain remission. The dose and duration of steroid treatment to prolong time between relapses remains a subject of much debate, and patients continue to experience a high prevalence of steroid-related morbidity. Various steroid-sparing immunosuppressive drugs have been used in clinical practice; however, there is marked practice variation in the selection of these drugs and timing of their introduction during the course of the disease. Therefore, international evidence-based clinical practice recommendations (CPRs) are needed to guide clinical practice and reduce practice variation. The International Pediatric Nephrology Association (IPNA) convened a team of experts including pediatric nephrologists, an adult nephrologist, and a patient representative to develop comprehensive CPRs on the diagnosis and management of SSNS in children. After performing a systematic literature review on 12 clinically relevant PICO (Patient or Population covered, Intervention, Comparator, Outcome) questions, recommendations were formulated and formally graded at several virtual consensus meetings. New definitions for treatment outcomes to help guide change of therapy and recommendations for important research questions are given.

Outcomes and risk factors for death among hospitalized children and adolescents with kidney diseases and COVID-19: an analysis of a nationwide database

BACKGROUND

Patients with kidney diseases (KD) appear to be at particularly high risk for severe COVID-19. This study aimed to characterize the clinical outcomes and risk factors for COVID-19-related death in a large cohort of hospitalized pediatric patients with KD.

METHODS

We performed an analysis of all pediatric patients with KD and COVID-19 registered in SIVEP-Gripe, a Brazilian nationwide surveillance database, between February 16, 2020, and May 29, 2021. The primary outcome was time to death, which was evaluated considering discharge as a competitive risk by using cumulative incidence function.

RESULTS

Among 21,591 hospitalized patients with COVID-19, 290 cases (1.3%) had KD. Of these, 59 (20.8%) had a fatal outcome compared with 7.5% of the non-KD cohort (P < 0.001). Pediatric patients with KD had an increased hazard of death compared with the non-KD cohort (Hazard ratio [HR] = 2.85, 95% CI 2.21-3.68, P < 0.0001). After adjustment, the factors associated with the death among KD patients were living in Northeast (HR 2.16, 95% CI 1.13-4.31) or North regions (HR 3.50, 95% CI 1.57-7.80), oxygen saturation < 95% at presentation (HR 2.31, 95% CI 1.30-4.10), and presence of two or more associated comorbidities (HR 2.10, 95% CI 1.08-4.04).

CONCLUSIONS

Children and adolescents with KD had a higher risk of death compared with the non-KD cohort. The higher risk was associated with low oxygen saturation at admission, living in socioeconomically disadvantaged regions, and presence of other pre-existing comorbidities. A higher resolution version of the Graphical abstract is available as Supplementary information.

Kidney injury associated with COVID-19 infection and vaccine: A narrative review

The respiratory tract is the main infection site for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), resulting in many admissions to intensive care centers in several countries. However, in addition to lung involvement, kidney injury caused by the novel coronavirus has proven to be a significant factor related to high morbidity and mortality, alarming experts worldwide. The number of deaths has drastically reduced with the advent of large-scale immunization, highlighting the importance of vaccination as the best way to combat the pandemic. Despite the undeniable efficacy of the vaccine, the renal side effects associated with its use deserve to be highlighted, especially the emergence or reactivation of glomerulopathies mentioned in some case reports. This study aimed to identify the main renal morphological findings correlated with COVID-19 infection and its vaccination, seeking to understand the pathophysiological mechanisms, main clinical features, and outcomes.

Os desafios da pandemia e a vacinação covid-19 na população pediátrica com doenças renais

Resumo A vacina covid-19 confere proteção direta, reduz as taxas de transmissão do vírus e de novas variantes. No Brasil, estão liberadas para a população pediátrica as vacinas Pfizer/BioNTech e a CoronaVac, ambas seguras, eficazes e imunogênicas. Pacientes pediátricos com síndrome nefrótica e covid-19 têm curso clínico regular sem complicações relacionadas ao uso de esteroides ou vacinas. Esses pacientes, com ou sem imunossupressão, não apresentam maior risco de covid-19 grave e o tratamento com esteroides é seguro. Os pacientes com doença renal crônica têm covid-19 mais leve, sem necessidade de hospitalização. A resposta vacinal pode ser reduzida e/ou a duração dos anticorpos pós-vacinação pode ser menor do que na população geral. Entretanto, a vacina covid-19 está recomendada, considerando o risco de exposição. Acredita-se que pacientes com síndrome hemolítico-urêmica teriam maior risco de covid-19 grave. A vacina é recomendada, embora dados específicos sobre segurança e eficácia da vacina covid-19 sejam limitados. Há concordância que os benefícios da imunidade induzida superam quaisquer riscos da imunização. A vacina covid-19 é recomendada para crianças e adolescentes candidatos ao transplante renal ou já transplantados. Esses pacientes têm resposta imunológica reduzida após a vacina, entretanto ela é recomendada porque os benefícios superam qualquer risco dessa vacinação. A recomendação atual no Brasil é a vacina de tecnologia RNA mensageiro. O objetivo deste documento é levar aos nefrologistas pediátricos os conhecimentos mais recentes sobre a vacinação contra contra-19 em crianças com doenças renais.

Spectrum of Kidney Injury Following COVID-19 Disease: Renal Biopsy Findings in a Single Italian Pathology Service

The onset of coronavirus disease (COVID-19) as a pandemic infection, has led to increasing insights on its pathophysiology and clinical features being revealed, such as a noticeable kidney involvement. In this study, we describe the histopathological, immunofluorescence, and ultrastructural features of biopsy-proven kidney injury observed in a series of SARS-CoV-2 positive cases in our institution from April 2020 to November 2021. We retrieved and retrospectively reviewed nine cases (two pediatric and seven adults) that experienced nephrotic syndrome (six cases), acute kidney injury (two cases), and a clinically silent microhematuria and leukocyturia. Kidney biopsies were investigated by means of light microscopy, direct immunofluorescence, and electron microscopy. The primary diagnoses were minimal change disease (four cases), acute tubular necrosis (two cases), collapsing glomerulopathy (two cases), and C3 glomerulopathy (one case). None of the cases showed viral or viral-like particles on ultrastructural analysis. Novel and specific histologic features on kidney biopsy related to SARS-CoV-2 infection have been gradually disclosed and reported, harboring relevant clinical and therapeutic implications. Recognizing and properly diagnosing renal involvement in patients experiencing COVID-19 could be challenging (due to the lack of direct proof of viral infection, e.g., viral particles) and requires a proper integration of clinical and pathological data.