Noncongophilic Fibrillary Glomerulonephritis in a Cat

Abstract

This report describes an uncommon case of nonamyloidotic fibrillary glomerulonephritis. A 5-year-old female European cat was presented with nephrotic syndrome. Serum biochemistry and urinalysis revealed a mild increase in cholesterol, low total protein, severe hypoalbuminemia, and high proteinuria with a high protein-to-creatinine ratio. An histologic examination revealed an interstitial nephritis and a diffuse glomerulonephritis, with multifocal thickening of the Bowman's capsule. Transmission electron microscopy showed widespread fibrillary deposits in the glomerular basement membrane and in the mesangium. These fibrils ranged between 18 and 26 nm in diameter and were Congo red negative, which allowed their differentiation from amyloid. Immunohistochemistry demonstrated expression for immunoglobulin M (IgM) and immunoglobulin G (IgG) within the mesangium. Renal deposits of Congo red-negative amyloid-like fibrils have been described in humans, horses, monkeys, and dogs. This is the first report of noncongophilic fibrillary glomerulopathy in a cat.

The use of telmisartan in combination therapy in the management of nephrotic syndrome due to non‐immune‐mediated glomerulonephropathy in a young cat

“…There are, however, only rare case reports of cats with non‐immune‐mediated glomerulopathies 6,22,30 . A few of the reports on glomerular disease in cats document trial treatment with corticosteroids in addition to benazepril; one cat with immune‐mediated glomerulonephritis was euthanased within 1 month of treatment, 6 and one case of feline PLN with non‐immune‐mediated glomerulonephritis (renal biopsies reported changes resembling FSGS) died 32 months after biopsy, 22 although the dose of prednisone used was not stated in either report. An additional case report describes minimal change glomerulopathy in a 6‐year‐old cat following treatment with imatinib 30 .…”

“…Several case reports document the high mortality rate associated with glomerular disease and nephrotic syndrome in young cats. [6][7][8]22,28,29 There are, however, only rare case reports of cats with non-immune-mediated glomerulopathies. 6,22,30 A few of the reports on glomerular disease in cats document trial treatment with corticosteroids in addition to benazepril; one cat with immune-mediated glomerulonephritis was euthanased within 1 month of treatment, 6 and one case of feline PLN with non-immunemediated glomerulonephritis (renal biopsies reported changes resembling FSGS) died 32 months after biopsy, 22 although the dose of prednisone used was not stated in either report.…”

“…Glomerular disease is more common in dogs, often associated with severe proteinuria 5 . There are occasional reports of immune‐mediated glomerular disease in cats, with invariably poor outcomes 6–8 . With the exception of amyloidosis, non‐immune‐mediated glomerulonephropathies are rarely reported in cats.…”

Glomerular Injury in Domestic Cats and the Iberian Lynx (Lynx pardinus): A Comparative Review

“…The first step for diagnosis is to differentiate amyloid from other fibrillary deposits with either specific stains such as Congo red or ultrastructural evaluation (Korbert et al, 1994). To date glomerular amyloidosis, collagenofibrotic glomerulopathy and noncongophilic fibrillary glomerulopathy have been described in the domestic cat (Boyce et al, 1984;DiBartola et al, 1986;Nakamura et al, 1996;Cavana et al, 2008).…”

“…The exact chemical nature of the fibrils remains unknown (Alpers, 1992;Schwartz et al, 2002;Hvala et al, 2003). A single case of noncongophilic fibrillary glomerulonephritis has been reported in an adult female European shorthair cat with clinical evidence of renal disease (Cavana et al, 2008). The renal lesions consisted of thickened glomerular capillary basement membranes and Bowman´s capsules.…”