CRP-37

CRP-37

Clinical History

The patient is a 60 year old black male. Cadaveric renal transplant three months ago. Original disease was membranous glomerulonephritis. Biopsy one month ago showed Banff I-B acute rejection. Baseline creatinine was 1.8. Following treatment for rejection creatinine decreased from 3.3 to 2.4, but it never returned to baseline.

Gross Description

Received in transport media is one core measuring 14 x 1 mm, which is entirely submitted for light microscopy.

Pathology

Case CRP-037 IHC BK polyomavirus

Microscopic Description, Immunofluorescence, and Electron Microscopy

Microscopic Description

Light Microscopy

Sections contain one fragment of mostly renal medulla with small portions of cortex. There are only four glomeruli in the three levels. All of these are unremarkable. There is patchy interstitial inflammation and numerous examples of tubulitis are identified. The most severely involved tubules contain seven to eight lymphocytes in cross section. There is interstitial edema, and trichrome stain shows mild focal interstitial fibrosis. However, most of the striking change in this biopsy is in the tubular epithelium. A number of the epithelial cells are swollen and contain enlarged nuclei. Occasional intranuclear inclusions are identified, and a few tubular epithelial cells also contain cytoplasmic granules. Occasional mitoses are noted in the epithelium. An immunohistochemical stain for BK polyomavirus is positive in the tubular epithelium, and the control is adequate. Stains for CMV, Epstein-Barr virus, herpes simplex, and adenovirus are negative with adequate controls. Only a few arterioles are present in the sample, and they are unremarkable.

Electron Microscopy

Following examination of the tissue submitted for light microscopy, the remaining tissue was removed from the paraffin block and reprocessed for electron microscopy. This yielded four thick sections with four glomeruli, but two of these are obsolete. Tubular epithelial cells with enlarged atypical nuclei are noted in several of the thick sections. Ultrastructural examination reveals occasional degenerated tubular epithelial cells with clear nuclei, but no definitive viral particles are identified.

Diagnosis and Comments

Kidney, allograft, needle biopsy – Moderate acute interstitial rejection, Banff grade 1-A. - BK polyomavirus infection.

These features are most consistent with two distinct lesions. There is still significant acute interstitial rejection, although comparison with the previous biopsy shows definitely less severe rejection than was present one week ago. However, in addition to the acute intestinal rejection there is BK polyomavirus infection. After identification of BK virus in this biopsy, the previous biopsy was stained for BK virus and rare positive tubular epithelial cells were noted.