ABSTRACT
Here, we report a case of abrupt onset of gross hematuria and nephrotic range proteinuria after the first dose of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination, which led to a diagnosis of immunoglobulin A nephropathy (IgAN). A Japanese woman in their forties with a significant medical history of occult blood by urine dipstick test (over the past 3 years) presented with fever, chills, shivering, marked thrombocytopenia, and gross hematuria 9 days after the first dose of the BNT162b2 mRNA vaccine (Pfizer) against SARS-CoV-2 infection. Although thrombotic microangiopathy (TMA) was first suspected as the cause of the severe thrombocytopenia, TMA was clinically excluded after two sessions of plasma exchange were performed. Renal biopsy was performed as the patient's platelet count improved. We made a diagnosis of acute worsening IgAN, triggered by the first dose of SARS-CoV-2 vaccination. In this case, we speculated that vaccine-induced immune activation may be involved in the exacerbation of occult IgAN, leading to the definite diagnosis. We should pay more attention to the development/worsening of clinically significant kidney disease after SARS-CoV-2 vaccination not only in those with known glomerular disease but also in those with only mild urinary abnormality.