Contributed by Hanady Zainah, MD1 and Ibrahim Batal, MD2
1Department of Internal medicine and 2Department of Pathology, University of Pittsburgh Medical Center
The patient is a 31 year-old male, status post-kidney transplant three years ago, who presented with increased creatinine. The patient was seen in an outside hospital and the biopsy was submitted to UPMC for consultation.
Examination of the allograft biopsy revealed interstitial inflammation (Figure 1) accompanied by moderate to severe tubular atrophy and interstitial fibrosis (Figure 2). The arteries showed intimal sclerosis (Figure 3). No intimal inflammation (arteritis) or necrosis were present. The glomeruli revealed focal and segmental sclerosis/ fibrosis and periglomerular fibrosis (Figure 4). No signs of glomerulitis (Figure 4) and/ or peritubular capillaritis were present. No definite nuclear inclusions were seen. However, relatively big and smudgy nuclei suggestive of viral cytopathic effects were found in the tubular epithelium (Figure 5).
Polyclonal C4d staining performed on formalin fixed paraffin embedded biopsy revealed diffuse staining (Figure 6). However, a careful high power microscopic examination revealed that the staining was mostly confined to tubular basement membranes (Figure 7) and Bowman's capsule (Figure 8). The relatively large nuclei were also present in the tubules that showed C4d basement membrane staining (Figure 7). In situ hybridization for BK virus DNA revealed nuclear staining in the tubular epithelium (Figures 9 and 10)