CRP-55

CRP-55

Clinical History

The patient is a 64-year-old female with a negative ANA, RA and ASOT.

History of weight loss and NSAID use. BUN 15, creatinine 0.7, creatinine clearance 90 ml/min, urinary protein 2.9 g/24 hr. BP: 120/82.

Gross Description

Received in Zeus fixative are two cores of tissue measuring 5 mm and S mm in length and 1 mm in diameter. These are entirely submitted for immunofluorescence. Received in Carson's fixative are two cores measuring 3 and 5 mm in length and 1 mm in diameter. Three 1-mm pieces are taken for EM, and the remainder is processed for light microscopy.

Pathology

Case CRP-055 Silver

Microscopic Description, Immunofluorescence, and Electron Microscopy

Microscopic Description

Light Microscopy

The specimen consists of two small fragments of renal cortex and a small portion of medulla. There are 15 glomeruli in the three levels examined. Two of these are obsolete, and one shows segmental sclerosis. Several glomeruli show advanced diffuse mesangial sclerosis with global collapse of the glomerular tuft. The remaining glomeruli show diffuse moderate increase in mesangial matrix and mild mesangial cell proliferation. The capillary basement membranes are markedly thickened, and occasional spikes on the epithelial surface are noted with the silver stain. There is no splitting. No glomerular necrosis is identified, and there are no crescents. There is mild patchy interstitial fibrosis, but tubular atrophy is minimal. There are no inflammatory infiltrates. The arterioles and small arteries show minimal thickening. A Congo red stain is negative.

Immunofluorescence

There are 10 glomeruli in the sections. One is obsolete, but the others show generally good preservation. There is focal 3+ mesangial and capillary loop staining for IgG, C3 and kappa light chain. There is similar staining that is graded 2+ for lambda light chain. There is trace mesangial staining for IgM. There is no staining for IgA or Clq. Tubular epithelium contains albumin droplets. There is no staining of the tubular basement membranes or vessels. A thioflavin T stain is negative.

Electron Microscopy

Three thick sections are available, but there is only one glomerulus. Ultrastructural examination reveals focal marked thickening of the glomerular basement membranes and large subepithelial collections of randomly oriented, nonbranching fibrils. These are similar to amyloid fibrils, but they are much thicker. The average diameter appears to be around 20 mm. There are also smaller deposits of these fibrils in the mesangial regions. No immune complex-type deposits are identified. The foot processes are completely fused.

Diagnosis and Comments

Kidney, needle biopsy - Fibrillary glomerulonephritis.

This is an extremely interesting case. The light microscopic, immunofluorescence, and electron microscopic findings are most consistent with fibrillary glomerulonephritis. This lesion is very uncommon in our experience; we only recall one other example of this in the last 7-8 years at UAB. The negative Congo red and thioflavine T stains, as well as the ultrastructural appearance of the fibrils, rules out amyloidosis. This histology is not consistent with an immune complex-mediated glomerulopathy.

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

The normal fibrinogen level is 184 to 412 mg/dL.

A normal alkaline phosphatase is 39 to 117 U/L.

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