Figure 5.

Pathologic findings of acute tubulointerstitial nephritis (patient 2). Light microscopy: (A) Mixed inflammatory cells infiltrated the tubular epithelium (tubulitis) and interstitium. Large numbers of mononuclear cells, neutrophils, eosinophils, and plasma cells were present (hematoxylin and eosin, ×400). (B) Acute tubular injury with red granular casts and string-like appearing casts was observed(Masson’s trichrome, ×400). (C) The casts show strong myoglobin positivity in the immunohistochemical stain (myoglobin, ×400). Electron microscopy: (D) The tubular casts have electron dense granules (×8000, 80 kv).