case_images: PMC9047909_01
case_images: Histological features of kidney biopsy showing diffuse active tubulointerstitial nephritis. (A) H&E slide. Marked lymphocytic infiltration in the interstitium with an admixture of neutrophils and plasma cells. Focal features of acute tubulitis are also present (arrowheads). Glomeruli reveal no apparent histological changes. (B) Electron microscopy sample is taken from interstitium between renal tubules. Few virus-like particles in size of ~120 nm with barely visible spikes are present intracellularly. Cross-sections of the particles contain interior electron-dense black dots which could be interpreted as helical nucleocapsid (lower magnification is available in Supplementary Figure 1). (C,D) Immunohistochemistry (IHC) for Anti-SARS-CoV-2 spike glycoprotein highlighted positive scattered immune cells in the interstitium of renal parenchyma (arrows). Rabbit polyclonal antibody against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike glycoprotein (ab272504, Abcam) was applied. Lung tissue of a deceased COVID-19-infected patient was used as a positive tissue control and a negative reagent control was performed on a consecutive biopsy tissue section to ensure sensitivity and specificity of the IHC test.
case_images: fped-10-861539-g0001.jpg
case_images: PMC9047909_01_fped-10-861539-g0001.jpg
case_images: F1
case_images: AIN was suspected and the patient underwent a kidney biopsy which revealed diffuse active interstitial nephritis with negative immunofluorescence and positive immunohistochemistry (IHC) staining for SARS-CoV-2 in interstitial cells, and SARS-CoV-2-like particles by electron microscopy (EM) (Figure 1, lower magnification available in Supplementary Figure 1).
case_images: Time course of serum creatinine since the admission to the hospital.
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case_images: PMC9047909_01_fped-10-861539-g0002.jpg
case_images: F2
case_images: Positive and negative controls used for IHC staining (including SARS-CoV-2 positive and negative lung tissue, a reagent with the omission of the primary antibody, and kidney tissue from a patient with AIN diagnosed in the pre-COVID-19 era) are presented in Supplementary Figures 2-4. The time course of serum creatinine since the admission to the hospital is summarized in Figure 2.