Decoy cells are seen in infection with
[A] CMV
[B] Adenovirus
[C] Polyoma Virus
[D] EBV
Answer = [C] Polyoma Virus (Ref: Heptinstall’s Pathology of the Kidney, 6th ed Page 1447e)
Renal allograft recipients are at definite risk of developing Polyoma Virus Nephropathy (PVN) and those patients can be identified by detecting some signs of polyoma virus activation in the urine and/or plasma.
Urine >> Patients with PVN show epithelial cells (eg Tubular epithelial cells) with polyomavirus inclusion in the urine and these are called as decoy cells.
Polyomavirus infections are caused in most cases by the BK virus strain, rarely may be caused by by JC virus, and hardly ever by SV40 virus ie we may say that Renal allograft tubular invasion with polyoma virus (PV) species is most commonly due to BK virus and presents with or without tubulointerstitial inflammation and fibrosis.
Confirmation of PVN is doen by detecting Polyoma virus large T antigen (SV40-T antigen) with IHC within cellular nucelei or by electron microscopy. EM shows 40-nm to 45-nm virions in nucleus or cytoplasm present as clusters or in paracrystalline arrays.
Epidemiological perspective and Prognosis of PVN> 5% to 8% of renal allografts are affected by PVN and presents as asymptomatic acute/chronic allograft dysfunction from 6 weeks - 5 years after transplant (Median 9months). Graft loss rates range from 45% to 65% due to irreversible interstitial fibrosis and tubular atrophy.
Decoy Cells > represent morphologic evidence of the (re)activation of polyomaviruses in the kidneys and urothelium of transplant
Bos recipients. Decoy cells have typical intranuclear
» Pl viral inclusion which sometimes occupies the
whole of nucleus and gives it a dark gelatinous
(Image Courtsy Dr J C Prolla)
featureless appearance, due to the
homogenization of its content. (See image) Note that viral infections may also be caused by HSV, adenovirus, or CMV and these mut be considered in the differential diagnosis of PVN.
An important DD is CMV infection — Differentiating Features are Given Below
Polyoma Virus eis Viral inclusion type Smudgy/ground-glass ++ + nuclear inclusion Central nuclear + +++ inclusion with halo Cytoplasmic inclusions - + Sites of viral replication/staining Tubular epithelial cells +4++ +++ Endothelial cells - ++ Inflammatory cells - +
Note >>Tubular epithelial cells are involved in both however inclusions in endothelial cells points towards CMV infection.