Spectrum of podocytopathies in new-onset nephrotic syndrome following COVID-19 disease: a report of 2 cases

Abstract

Background: Coronavirus disease-2019 (COVID-19) is an ongoing pandemic which has affected over 12 million people across the globe. Manifestations in different organs systems are being reported regularly. Renal biopsy findings in hospitalized COVID-19 patients presenting solely with acute kidney injury (AKI) have recently been described in published literature in few case reports. The findings include diffuse acute tubular injury (ATI) along with the glomerular lesion of collapsing glomerulopathy (CG). However, nephrotic syndrome as the presenting complaint of COVID-19 has not been reported widely, neither has any other glomerular lesion other than CG.

Case presentation: We describe the kidney biopsy findings of two patients who had recent diagnoses of COVID-19 and presented with new-onset nephrotic syndrome. Renal biopsy in both patients showed ATI (as in previous reports) and distinct glomerular findings on light microscopy - that of minimal change disease (MCD) initially in one patient followed by CG in a subsequent biopsy and CG at the outset in the other patient. The electron microscopic findings in both patients were that of severe podocytopathy (diffuse and severe podocyte foot process effacement).

Conclusion: Our cases highlight a novel clinical presentation of COVID-19 renal disease, not described before, that of new-onset nephrotic syndrome. While all published case reports describe CG as the glomerular pathology, we describe a non-CG pathology (MCD) in one of our cases, thereby adding to the repertoire of renal pathology described in association with COVID-19 patients. However, the exact mechanism by which podocyte injury or podocytopathy occurs in all such cases is still unknown. Optimal treatment options for these patients also remains unknown at this time.

Keywords: COVID-19; Collapsing glomerulopathy; Nephrotic syndrome; Podocytopathy.

Fig. 1

Images of case 1. a-d. First biopsy of case 1 – a. Biopsy core showing diffuse acute tubular injury in the form of epithelial flattening, intra-luminal dilatation and variably prominent tubular cell nuclei; background interstitium shows fibrosis intermixed with edema (Masson trichrome stain; original magnification, × 100); b. Representative glomerulus from the biopsy appearing completely unremarkable (PAS stain; original magnification, × 400); c. electron microscopy view of one glomerulus showing complete foot process effacement over adjacent capillary loops (original magnification, × 6800); and d. Electron microscopy view showing complete foot process effacement over 2 facing capillary loops (original magnification, × 18,500); e-f. Second biopsy of case 1 - e. Representative glomerulus showing global collapse of capillary loops associated with circumferential podocyte capping and podocyte hypertrophy/hyperplasia (Jones methenamine silver; original magnification, × 400), and f. Electron microscopy view of one glomerulus showing complete foot process effacement over adjacent capillary loops (original magnification, × 6800)

Fig. 2

Images of case 2. a. Biopsy core showing diffuse acute tubular injury, few tubules with microcystic change and a single glomerulus with slight capillary collapse and podocyte capping (H&E stain; original magnification, × 100); b. A representative glomerulus from the biopsy showing global collapse of capillary loops associated with podocyte hypertrophy/hyperplasia (Jones methenamine silver; original magnification, × 400); c. A profile of proximal tubule in one of the biopsy cores showing abundant bright protein reabsorption droplets within the tubular epithelial cytoplasms (Masson trichrome stain; original magnification, × 400); and d. Electron microscopy view showing complete foot process effacement over adjacent capillary loops (original magnification, × 4800)