Fig. 1

The pathological findings of the first renal biopsy. a Light microscopic examination showed 11 intact glomeruli (PAM stain, ×400). b, c A severe and diffuse infiltration of inflammatory cells composed of mainly plasma cells, lymphocytes, and neutrophils was observed in the interstitial compartment, together with mild to moderate fibrosis of the interstitium. Leukocyte casts, mainly neutrophils, were observed in the renal tubules (b, Masson’s trichrome stain, ×100, c hematoxylin-eosin stain, ×200). d Immunochemistry showed MPO-positive cells in the interstitial compartment (d MPO immunohistochemical staining, ×200). MPO, myeloperoxidase