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Kidney non-tumor

Infections / parasites

BK virus / polyomavirus

Reviewer: Nikhil Sangle, M.D. (see Reviewers page)
Revised: 1 September 2012, last major update September 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.


● Polyomaviruses are non-enveloped DNA viruses, 45 nm in diameter; members of papovavirus family, which also contain papillomavirus
● Polyomavirus BK is widely present in healthy individuals, but latent in kidneys, central nervous system and B cells
● Other polyoma viruses are JC (causes progressive multifocal leukencephalopathy) and SV40 (causes subclinical infections)
● JC and BK virus infection is very prevalent in the first 2 years after kidney transplant (J Res Med Sci 2011;16:916)
● Immunosuppression promotes reactivation of latent polyoma virus, leading to viral replication in renal tubular epithelial cells

Clinical features

● BKV strain of polyoma virus may cause renal failure in AIDS patients, is reactivated in <8% of renal transplant patients with heavy immunosuppression or rarely in other immunosuppressed patients
● Rarely occurs in nonrenal solid organ transplantation (Am J Transplant 2010;10:2324)
● Diagnose by PCR (but variant strains may affect quantitation of viral load, J Clin Microbiol 2011;49:4072); urinary decoy cell detection (Transplantation 2011;92:1018) and immunostains (SV40 immunostain crossreacts with JCV)
● Increased risk with ureteral stenting (Transplant Proc 2011;43:2641)
● Associated with interstitial nephritis, infection of glomerular epithelial cells and crescents (minority of cases)
● JC virus strain of polyoma virus usually not associated with renal damage (Hum Pathol 2001;32:656), but present in renal tissue in 6% of AIDS patients (Mod Pathol 2003;16:35)

Case reports

● 14 year old boy with AIDS and BK viral infection of lung and kidney causing diffuse alveolar damage and death (Am J Surg Pathol 2000;24:145)
● 31 year old IV drug user with AIDS and BK virus related renal failure (Arch Pathol Lab Med 1999;123:807)
● 53 year old with triple immunosuppressive therapy for transplant (Hum Pathol 2001;32:656)
● 62 year old man post-transplant for SLE induced renal disease (Arch Pathol Lab Med 2001;125:973)

Micro description

In non-transplanted kidney:
● Interstitial inflammation, atrophic tubules with large and eosinophilic nuclei

In allograft kidney:
● Viral cytopathic effect with large, homogenous and purple intranuclear inclusions, primarily in tubular epithelium (Hum Pathol 2004;35:367)
● No necrosis (as seen in HSV), no perinuclear halo (as seen in CMV)
● Also ischemic glomerulopathy (62%), aneurysmal dilation of glomerular capillaries (28%) and mild increase in mesangial matrix (23%)
● Viral cytopathic effect in parietal Bowmanís capsule (29%, including using BK immunostains), crescents (12%) and glomerulonephritis (3%)

Micro images



Various images

Figure 1: tubulointerstitial nephritis with lymphocytes and enlarged tubular epithelial cells
Figure 2: tubular cells have large smudged nuclei and basophilic chromatin
Figure 3: EM shows distinct intranuclear inclusion; 4: inclusion consists of crystalline arrays of nonenveloped, round, electron-dense particles, mean 45 nm in diameter, in loose crystalline lattices

Electron microscopy images

Tubular cell with numerous viral particles (inset: anti-SV40 antibody)

Differential diagnosis

● Rejection
● Other infection

End of Kidney non-tumor > Infections / parasites > BK virus / polyomavirus

Ref Updated: 6/26/12

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