KIDNEY, LEFT, PERCUTANEOUS NEEDLE BIOPSY
In summary, this 68 year old man presenting with nephrotic range proteinuria, chronic renal insufficiency, congestive heart failure secondary to non-ischemic left ventricular dysfunction, and diarrhea has on biopsy a non-amyloid, polyclonal immunoglobulin-derived fibrillary glomerulopathy. There is also superimposed chronic renal disease with approximately 40% global glomerular sclerosis and associated secondary tubulointerstitial changes.
In the most general sense, fibrillary glomerulopathy is a category of glomerular diseases that is defined by the ultrastructural feature of organized deposits of extracellular, non-branching microfibrils. The diseases encompassed within this group include amyloidosis, light chain deposition disease, cryoglobulinemia, systemic lupus erythematosus, fibrillary/immunotactoid glomerulopathy, and diabetic fibrillosis. These diseases share similar morphologic features by light microscopy, but differ in their immunophenotypic and ultrastructural characteristics.
By light microscopy fibrillary glomerulopathy demonstrates widened mesangium with cell proliferation and an increase in matrix. Progression to a lobular pattern and to total glomerular sclerosis is frequently seen. Crescents occur in approximately one-third of cases. Some patients show mild cellular proliferation and prominent acellular mesangial sclerosis, whereas others have marked capillary wall thickening. Stains for amyloid are consistently negative.
Fibrillary/immunotactoid glomerulopathy is characterized by deposition of fibrils ranging from 10 to 50 nanometers in diameter, deposited in the mesangium and/or the capillary basement membranes. Extraglomerular involvement is rare. In fibrillary glomerulopathy, the fibrils are thinner and haphazardly oriented; in immunotactoid GN, the fibrils are the size of microtubules and are arranged in a parallel configuration. By immunofluorescence, the fibrils are demonstrated to contain polyclonal immunoglobulin (usually IgG) and complement (usually C3), with a ribbon-like and smudgy, non-linear, non-granular staining pattern distributed in the mesangium and/or capillary walls.
The reported clinical data in one series of fibrillary glomerulopathy (S. S. Iskandar, et al) demonstrated a mean age of 49 years (age range 21 - 75 yrs), female predominance, and a marked Caucasian predominance. The most common clinical feature was nephrotic syndrome, however, many patients had concomitant hematuria, renal insufficiency, and hypertension. Antinuclear antibodies were positive in only 12% of patients, and serum complement levels were uniformly normal. None of the patients had evidence of extrarenal disease, which is in contrast to immunotactoid GN which has a recognized association with some autoimmune and lymphoproliferative disorders. The mean renal survival after a follow-up of 24 months for fibrillary glomerulopathy was only 48%, with all but 4 patients developing at least some degree of renal insufficiency. 6/28 patients receiving corticosteroid therapy showed no benefit compared to the untreated group with respect to progression to renal failure.