In a renal allograft biopsy with this finding, what is your diagnosis?
The biopsy shows severe intimal arteritis on a toluidine blue section, which is consistent with Grade 2B TCMR. This is a reminder that sometimes the diagnostic lesion will only be present on toluidine blue sections, and these should always be examined. LM sections showed extensive interstitial hemorrhage (Figure 2), which is often a clue that underlying vascular lesions are present.
The biopsy also showed severe tubulitis (Figure 3), mild glomerulitis, mild peritubular capillaritis and a positive C4d (Figure 4).
Vascular rejection lesions can be seen in association with both acute T cell- and antibody-mediated rejection processes. Based on current Banff criteria, the biopsy findings are diagnostic of acute T cell-mediated rejection (grade 2B). However, the presence of glomerulitis, peritubular capillaritis and positive C4d also raises the possibility of concurrent antibody-mediated rejection. Donor specific antibodies were reportedly negative a month prior; repeat testing results were pending at the time of biopsy.
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