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Congenital nephrotic syndrome (CNS) is a rare disease defined as heavy proteinuria, hypoalbuminemia, hyperlipidemia, and edema presenting in the first three months of life. It is most commonly caused by mutations in the NPHS1 gene associated with nephrotic syndrome type 1, also known as Finnish-type CNS, which is inherited in an autosomal recessive manner. Symptomatic treatment with intravenous albumins, vitamins, minerals, nutritional, and hormonal supplementation and treatment of complications are mandatory. Children refractory to the symptomatic treatment are recommended to undergo nephrectomy and renal replacement therapy, preferably renal transplantation. We report on a child with Finnish type CNS with a NPHS1 mutation, which is the first case confirmed by genetic study in Slovenia. We showed for the first time that homozygous mutation c.2928-3del in the NPHS1 gene caused exon 22 skipping, leading to a truncated protein and Fin-minor phenotype.

Background Sarcoidosis is characterized by granulomatous inflammation in multiple organs. Renal involvement is rare, and granulomatous tubulointerstitial nephritis (TIN) is the predominant histologic feature. TIN is also a hallmark of tubulointerstitial nephritis and uveitis (TINU) syndrome. Diagnoses of both sarcoidosis and TINU syndrome are usually made by exclusion and by combining clinical and histological findings, and often remain misdiagnosed. The aim of this retrospective study was to determine the characteristics of renal sarcoidosis and TINU syndrome in Slovenia in the last decade (2010 - 2020). Materials and methods A thorough search of the national database of renal biopsies from January 2010 to December 2020 was performed. Inclusion criteria were TIN and a clinical history of either sarcoidosis or TINU syndrome. To compare the characteristics of our cohort with others, we also reviewed the global literature reported since 2010. Results 13 patients (9 female, 4 male) were included in our study. Indications for kidney biopsy were acute kidney injury (n = 8), acute exacerbation of chronic kidney disease (n = 4), and proteinuria (n = 1). Seven patients had clinical and histological evidence of sarcoidosis, and 6 patients were classified as having TINU syndrome. All patients were treated with corticosteroids. Of the 13 patients, 11 had improved kidney function 6 months after treatment, and proteinuria decreased in 9 patients. One patient was on dialysis at the time of diagnosis and remained so thereafter. Conclusion Renal sarcoidosis and TINU syndrome are rare but important causes of kidney injury, with a favorable long-term prognosis if properly diagnosed and treated in a timely manner.

Background Thin basement membrane nephropathy (TBMN) is a disorder characterized by ultrastructural abnormalities of the glomerular basement membrane (GBM), representing a spectrum of genetic and clinical phenotypes ranging from benign hematuria to proteinuria and chronic kidney disease. Recent studies have shown that a significant percentage of patients who initially present with hematuria later develop proteinuria and worsening renal function. Materials and methods We retrospectively analyzed records of patients diagnosed with TBMN, including their clinical, laboratory, and histological features, in Slovenia from 2015 to 2020. Results TBMN was the main diagnosis at kidney biopsy in 34 (65%) of 52 included patients, while in 18 patients (35%) TBMN was diagnosed in addition to other renal diseases. In the isolated TBMN group, 29 of 34 patients had glomerulosclerosis (global, global and segmental, segmental only) accompanied by interstitial fibrosis/tubular atrophy of varying degrees. 13 patients with isolated TBMN had signs of advanced chronic kidney disease at the time of diagnosis, with estimated glomerular filtration rate Conclusion Ultrastructural examination showing diffuse thinning of the GBM is crucial for the TBMN diagnosis. TBMN was the main diagnosis of kidney biopsy in 2/3 of our patients, while it was accompanied by other renal diseases in 1/3. Up to 1/3 of patients with isolated TBMN had evidence of advanced chronic kidney disease at the time of diagnosis.

Background: There is increasing evidence that identification of SARS-CoV-2 virions by transmission electron microscopy could be misleading due to the similar morphology of virions and ubiquitous cell structures. This study thus aimed to establish methods for indisputable proof of the presence of SARS-CoV-2 virions in the observed tissue. Methods: We developed a variant of the correlative microscopy approach for SARS-CoV-2 protein identification using immunohistochemical labelling of SARS-CoV-2 proteins on light and electron microscopy levels. We also performed immunogold labelling of SARS-CoV-2 virions. Results: Immunohistochemistry (IHC) of SARS-CoV-2 nucleocapsid proteins and subsequent correlative microscopy undoubtedly proved the presence of SARS-CoV-2 virions in the analysed human nasopharyngeal tissue. The presence of SARS-CoV-2 virions was also confirmed by immunogold labelling for the first time. Conclusions: Immunoelectron microscopy is the most reliable method for distinguishing intracellular viral particles from normal cell structures of similar morphology and size as virions. Furthermore, we developed a variant of correlative microscopy that allows pathologists to check the results of IHC performed first on routinely used paraffin-embedded samples, followed by semithin, and finally by ultrathin sections. Both methodological approaches indisputably proved the presence of SARS-CoV-2 virions in cells.

Background: Anticoagulant-related nephropathy (ARN) is a form of acute kidney injury that mainly occurs in patients with previously unrecognized glomerular disease in addition to excessive anticoagulation. Since a renal biopsy is not performed in most cases, the diagnosis is often presumptive. Methods: Here, we present the characteristics of a national Slovenian patient cohort with histologically verified ARN, from the first case in 2014 to December 2020, and a review of the current literature (Pubmed database). Results: In Slovenia, ARN has been detected in 13 patients, seven of whom were treated with coumarins, and others with direct oral anticoagulants. In seven patients, ARN appeared after excessive anticoagulation. As many as 11 patients had underlying IgA nephropathy. Similar to the global data presented here, the pathohistological impairment associated with pre-existing glomerulopathy was mild and disproportionate to the degree of functional renal impairment. The majority of our patients with ARN experienced severe deterioration of renal function associated with histological signs of accompanying acute tubular injury, interstitial edema, and occlusive red blood cell casts. These patients were treated with corticosteroids, which (in addition to supportive treatment and discontinuation of the anticoagulant drug) led to a further improvement in renal function. Conclusions: Anticoagulant therapy combined with a pre-existing glomerular injury may lead to ARN. In addition to discontinuation of the anticoagulant and supportive care, corticosteroids, which are currently listed in only a few cases in the world literature, may have a positive influence on the course of treatment. However, the benefits of steroid treatment must be weighed against the risk of complications, especially life-threatening infections.