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 treated with metformin and insulin. Diabetic retinopathy, urinary protein, and occult blood were absent. Serum creatinine (sCr) values remained in the range of 1.0–1.3 mg/dL (estimated glomerular filtration rate, 46–62 mL/min/1.73 m2). He had received three COVID-19 vaccines at four-month intervals. He had no family history of renal diseases. Two of the vaccines were from Pfizer-BioNTech and one was from Moderna. Adverse reactions to the last three vaccinations were not serious, including joint pain and transient fever. Five months after receiving the third vaccine, he received a fourth COVID-19 vaccine. Three days after receiving the fourth COVID-19 vaccine (Pfizer-BioNTech), he became fatigued and visited a local doctor four days later. The sCr level was 4.72 mg/dL, and he was given supplemental fluids for dehydration. The next day, the sCr level was further elevated and the patient was referred to our hospital, where he was urgently hospitalized. A physical examination revealed no remarkable findings. The blood test results showed an elevated white blood cell count (9600 cells /µL), normal hemoglobin level (14.7 g/dL), renal dysfunction (sCr, 7.09 mg/dL), elevated inflammatory response (C-reactive protein, 1.15 mg/dL), and poor glycemic control (HbA1c 7.8%). Anti-neutrophil cytoplasmic, anti-nuclear, and anti-glomerular basement membrane antibodies were absent. The urinary N-acetyl-β-D-glucosaminidase level was normal (50 µg/L; reference value, < 289 µg/L). However, the N-acetylglucosaminidase level was mildly elevated (37.2 IU/L; reference value, 0.7–11.2 IU/L). Glomerular hematuria was present, and urinary protein excretion was approximately 1 g/day. Computed tomography revealed no renal atrophy or hydronephrosis. Rapidly progressive glomerulonephritis (RPGN) from vasculitis was suspected. Therefore, methylprednisolone pulse therapy (500 mg/day) was administered for three days from the day of admission, followed by prednisone (60 mg/day). A renal biopsy was performed on the second day he was hospitalized.
Twenty-two glomeruli were collected, two of which had global sclerosis. No abnormal findings were observed in the other glomeruli. The tubules showed vacuolar degeneration (Fig. 1a and 1b) with mild lymphocyte infiltration (Fig. 1c). Interstitial fibrosis was unremarkable in the interstitium and tubules (Fig. 1d). Immunoglobulin (Ig) G, IgA, C1q, and C3 assay results were negative for the glomerulus, implying no glomerular involvement. Pathologically, the findings indicated acute tubular injury. Therefore, a diagnosis of ATI from COVID-19 vaccination was made. Prednisone was discontinued the day after the pathology results became known (prednisolone was administered for five days). The patient’s sCr level improved to 1.14 mg/dL 14 days after vaccination (at discharge), then to 1.00 mg/dL 19 days after vaccination. A chart of the treatment process is shown in Fig. 2.