CRP-59

CRP-59

Clinical History

The patient is a 29-year-old male. BUN 58, creatinine 5.5, creatinine clearance 27 ml/min, urinary protein 9 g/day. Serum creatinine was normal 6 months ago.

Gross Description

Received in transport media is one core measuring 15 x 2 mm. Three 1-mm pieces are taken for EM, and the remaining tissue is bisected and equally divided for immunofluorescence and light microscopy.

Pathology

Case CRP-059 Silver

Microscopic Description, Immunofluorescence, and Electron Microscopy

Microscopic Description

Light Microscopy

Sections contain two fragments of renal cortex with twenty-nine glomeruli in the three levels. None of these are obsolete, although one shows segmental collapse and hyalinosis (level #1}. Most of the glomeruli demonstrate marked mesangial nodular sclerosis, which is usually accompanied by mesangial proliferation. However, some of the nodules appear somewhat acellular. None have the classical appearance of Kimmelstiel -Wilson nodules. The glomerular basement membranes appear irregularly thickened, but the silver stain shows no spikes or splitting. There is no glomerular necrosis, and no crescents are identified. PASH and trichrome stains show diffuse moderate interstitial fibrosis and tubular atrophy. The tubular basement membranes are generally very thick and ribbon-like. In addition to the chronic tubular injury, many of the tubules show more acute degenerative changes consisting of irregular dilatation, epithelial simplification and epithelial cell sloughing. One tubule is markedly dilated and contains amorphous debris in the lumen. However, true microcystic change is not noted. Occasional mononuclear inflammatory cells are noted in the interstitium, but there is no tubulitis. There is mild arteriolosclerosis.

Immunofluorescence

There are five glomeruli in the sections. There is 4+ linear staining for kappa light chain in the glomerular and tubular basement membranes. There is 2+ focal mesangial staining for IgM. There is no glomerular staining for IgG, IgA, Clq, C3, albumin or lambda. There is focal staining for C3 in the vessels.

Electron Microscopy

Five thick sections are available, but there is only glomerulus. The tubular basement membranes stain intense y. Ultrastructural examination confirms the increased mesangial matrix, and there is granular electron-dense material in the mesangium. The glomerular basement membranes are irregularly thickened, and the foot processes are completely effaced. Finely granular electron dense material is noted along the endothelial surface of many capillary loops.

There is extensive deposition of similar finely granular electron dense material within the tubular basement membranes and Bowman's capsule, as well as in the interstitium. No typical immune complex deposits are identified.

Diagnosis and Comments

Kidney, needle biopsy- Light chain deposition disease, kappa type.

These features are most consistent with light chain deposition disease, and the immunofluorescence staining strongly suggests that it is kappa light chain. This is a very unusual lesion in someone this age, but the immunofluorescence and electron microscopic findings are pathognomonic. The presence of excessive light chains would explain both the chronic and acute tubular injury. There is moderate tubulointerstitial scarring.

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

Nodular hyperplasia of the prostate--characterized by large discrete prostatic nodules--is a common disorder in men over 50 years of age. The nodules cause the prostate to be enlarged and to have an increased weight. The human prostate is surrounded by a restrictive capsule. These nodules cause increased pressure within the capsule which leads to constriction of the urethra as it passes through the prostate. Urethral constriction leads to retention of urine.