CRP-12

CRP-12

Clinical History

The patient is a 15 year old male. Urinary protein 7.03 g/day, BUN 16, creatinine 1.6.

Gross Description

Received in transport medium are three cores measuring 8, 12, and 13 mm in length and l mm in diameter. These cores appear to be medulla under the dissecting microscope. A 1-mm piece is taken from the largest core for EM, and the remaining tissue is submitted for light microscopy. No tissue is submitted for immunofluorescence.

Pathology

Case CRP-012 Silver

Microscopic Description, Immunofluorescence, and Electron Microscopy

Microscopic Description

Light Microscopy

The specimen consists of three fragments of renal cortex that contain from thirty to thirty-seven glomeruli per level. Approximately 50% of the glomeruli contain cellular crescents, most of which are only a few cell layers thick and cover less than half of Bowman's capsule. All of the glomeruli show diffuse increase in mesangial matrix and hypercellularity. The capillary basement membranes appear thickened, but the silver stain does not show spike formation along the epithelial surfaces. The trichrome stain shows fuchsinophilic deposits along the endothelial surfaces in some capillary loops. There is focal necrosis, usually associated with cellular crescents. The PASH and trichrome stains show diffuse interstitial edema and scattered inflammatory infiltrates. A number of examples of mild tubulitis are identified. There is only mild focal interstitial fibrosis. The vasculature is unremarkable.

Electron Microscopy

One thick section containing three glomeruli is available. Ultrastructural examination reveals marked increase in mesangial matrix and hypercellularity. However, the most striking feature is the marked GBM thickening and replacement of the lamina densa by electron dense material. Most of the capillary basement membranes are involved, but there are occasional normal segments connecting the affected segments. Similar deposits are identified in Bowman's capsule. No tubular basement membrane deposits are identified. No discrete immune complex deposits are noted. The foot processes are completely effaced.

Diagnosis and Comments

Kidney, needle biopsy - Dense deposit disease (type II membranoproliferative glomerulonephritis).

These findings are most consistent with dense deposit disease (type II membranoproliferative glomerulonephritis), which is a very rare lesion. Most patients progress to renal failure in 5-10 years, but a few maintain good renal function for a long time. Unfortunately, the development of glomerular crescents is associated with rapidly progressive renal failure. Although the glomerular lesion is extremely active, there is no significant glomerulosclerosis, and the degree of interstitial fibrosis is still relatively mild.

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

An infiltrate is an accumulation of cells in the lung parenchyma--this is a sign of pneumonia.

Renal failure is the severe reduction of renal function and often leads to reduced urinary output.