Two adolescents with frequently relapsing nephrotic syndrome newly diagnosed after SARS-CoV-2 vaccination: case report and literature review.

Even though several cases of new-onset nephrotic syndrome following vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been reported, none have included the medium- to long-term prognosis of the patients. Here, we report the prognoses of two adolescents, aged 14 and 15 years, who developed nephrotic syndrome soon after receiving the Pfizer-BioNTech SARS-CoV-2 vaccine. Both patients were diagnosed with nephrotic syndrome after developing edema within a few days post-SARS-CoV-2 vaccination. Although they achieved rapid and complete remission with prednisolone therapy, they developed frequently relapsing nephrotic syndrome and were initiated on cyclosporine. In one patient, frequent relapses occurred while taking cyclosporine, requiring rituximab to maintain remission. Measurements of antibody titers against the spike protein of the SARS-CoV-2 vaccine taken over time revealed significantly lower titers in both patients compared with those in healthy individuals. Furthermore, each patient was infected with SARS-CoV-2 about 12 months post vaccination, with mild symptoms. Nephrotic syndrome did not recur in either patient. We also reviewed 49 published cases of patients who developed nephrotic syndrome after SARS-CoV-2 vaccination, compared to our pediatric cases, there are no cases of recurrence with the same frequency in adult cases, and it is desirable to accumulate and compare more pediatric cases in the future.