CRP-36

CRP-36

Clinical History

Cadaveric renal transplant three months ago. Primary renal disease was polycystic kidney disease. History of CMV infection. BUN 50, creatinine 1.9.

Gross Description

Received in transport media is one core measuring 8 x 1 mm. The entire specimen is submitted for light microscopy.

Pathology

Case CRP-036 IHC-CMV

Microscopic Description, Immunofluorescence, and Electron Microscopy

Microscopic Description

Light Microscopy

The specimen consists of a fragment of renal cortex that contains thirty-three glomeruli in the three levels. None of these are obsolete, and none show segmental sclerosis. Most of the glomeruli show a striking pattern of glomerular injury. The principle features are diffuse endothelial cell hypertrophy and necrosis, infiltration by mononuclear cells, and mesangiolysis. The PASH stain shows peculiar webs of PAS· positive material in the capillary lumina. Most of the glomerular capillary lumina are obliterated. No viral inclusions axe identified in any of these cells. In addition to the glomerular injury, there it also severe acute interstitial rejection. There is diffuse interstitial edema, and numerous examples of emperipolesis are noted. The most severely involved tubules contain more than ten lymphocytes in cross-section. There is minimal interstitial fibrosis, and there is no significant tubular atrophy. Only a few small vessels and arterioles area present. None of these show evidence of vascular rejection. Immunohistochemical staining for cytomegalovirus (CMV) is positive in five glomeruli. The staining is confined to endothelial cells. There is no staining in the tubular epithelium. The positive and negative controls are adequate.

Electron Microscopy

Following examination of the tissue submitted for light microscopy, a portion of the remaining issue was removed from the paraffin block and submitted for electron microscopy. This yielded three thick sections with a total of three glomeruli. One of these is obsolete, but the other two are relatively well preserved. Unfortunately neither contains the swollen endothelial cells noted by light microscopy. There is minimal increase in mesangial matrix, and the glomerular basement membranes are unremarkable. The foot processes are intact. No viral particles are identified in the glomerular endothelial cells.

Diagnosis and Comments

Kidney, allograft, needle biopsy·- Moderately severe acute interstitial rejection, Banff grade I-B. - Acute allograft glomerulopathy (CMV glomerulopathy).

These histologic features are most consistent with two distinct lesions. There is severe acute interstitial rejection, and the degree of tubulitis corresponds to Banff grade I-B. However, there is also a very unusual glomerular lesion that has been described in the literature as “acute allograft glomerulopathy”. This is a distinctive glomerular injury in renal allografts that has been associated with CMV viremia, although similar changes have occasionally been described in the absence of CMV infection. Interestingly, the published cases almost never show evidence of CMV in the glomerular cells. Typically in the published cases no viral particles are detectable by electron microscopy, and no viral antigens are detected. In contrast, this biopsy shows definite immunohistochemical staining for CMV. However, electron microscopic examination failed to identify viral particles.

Blood urea nitrogen (BUN) is used as a measure of the glomerular filtration rate and is increased in renal failure.