Case report: a 5-year-old with new onset nephrotic syndrome in the setting of COVID-19 infection.

BACKGROUND: This is a case report of an asymptomatic SARS-CoV-2 infection associated with new-onset nephrotic syndrome in a pediatric patient. This is the third case of new-onset nephrotic syndrome in children associated with SARS-CoV-2 infection, but is the first case report describing a new-onset nephrotic syndrome presentation in a patient who had asymptomatic COVID-19 infection. CASE PRESENTATION: This is a case of a previously healthy 5 year old female who presented with new-onset nephrotic syndrome in the setting of an asymptomatic COVID-19 infection. She presented with progressive edema, and laboratory findings were significant for proteinuria and hypercholesterolemia. She was treated with albumin, diuretics, and corticosteroid therapy, and achieved clinical remission of her nephrotic syndrome within 3 weeks of treatment. Though she was at risk of hypercoagulability due to her COVID-19 infection and nephrotic syndrome, she was not treated with anticoagulation, and did not develop any thrombotic events. CONCLUSIONS: Our case report indicates that SARS-CoV-2 infection could be a trigger for nephrotic syndrome, even in the absence of overt COVID-19 symptoms.

Glomerular filtration barrier dysfunction in a self-limiting, RNA virus-induced glomerulopathy resembles findings in idiopathic nephrotic syndromes.

Podocyte injury has recently been described as unifying feature in idiopathic nephrotic syndromes (INS). Puumala hantavirus (PUUV) infection represents a unique RNA virus-induced renal disease with significant proteinuria. The underlying pathomechanism is unclear. We hypothesized that PUUV infection results in podocyte injury, similar to findings in INS. We therefore analyzed standard markers of glomerular proteinuria (e.g. immunoglobulin G [IgG]), urinary nephrin excretion (podocyte injury) and serum levels of the soluble urokinase plasminogen activator receptor (suPAR), a proposed pathomechanically involved molecule in INS, in PUUV-infected patients. Hantavirus patients showed significantly increased urinary nephrin, IgG and serum suPAR concentrations compared to healthy controls. Nephrin and IgG levels were significantly higher in patients with severe proteinuria than with mild proteinuria, and nephrin correlated strongly with biomarkers of glomerular proteinuria over time. Congruently, electron microcopy analyses showed a focal podocyte foot process effacement. suPAR correlated significantly with urinary nephrin, IgG and albumin levels, suggesting suPAR as a pathophysiological mediator in podocyte dysfunction. In contrast to INS, proteinuria recovered autonomously in hantavirus patients. This study reveals podocyte injury as main cause of proteinuria in hantavirus patients. A better understanding of the regenerative nature of hantavirus-induced glomerulopathy may generate new therapeutic approaches for INS.