Recently, there have been reports of new cases of acute kidney injury (AKI) after coronavirus disease 2019 (COVID-19) vaccination. Podocytic damage, IgA nephropathy, vasculitis, tubulointerstitial damage, and thrombotic microangiopathy have been reported as the causes. However, there are no reports of acute tubular injury (ATI) as the sole cause of AKI. In this case, a 54-year-old man with type 2 diabetes visited a local physician. He was highly obese with a body mass index of 36 kg/m2. He was

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... reated with metformin and insulin. Diabetic retinopathy, urinary protein, and occult blood were absent. He had received four COVID-19 vaccines; three were from Pfizer and one from Moderna. He was referred to our hospital 5 days after receiving the fourth dose of the Pfizer-BioNTech COVID-19 vaccine. He had stage 3 AKI. Urinary findings revealed the presence of new proteinuria and glomerular occult blood. Steroids were introduced on the day of admission for rapidly progressive glomerulonephritis. A renal biopsy was performed on the second day, with results obtained on the fifth day revealing no findings other than ATI. The patient was therefore deemed unamenable to steroids. After steroid discontinuation, renal function recovered spontaneously, and urinalysis abnormalities disappeared. In this case, ATI was the sole pathogenesis of COVID-19 vaccine-induced AKI, and treatment with immunosuppressive drugs was not necessary.