NOTE Pathology

Progression of to End-Stage Disease in a Cat with Nephrotic Syndrome

Junichi KAMIIE1), Atsuko HAISHIMA2), Kaoru INOUE2), Kikumi OGIHARA3), Mihoko ONO2), Kyohei YASUNO2), Ryosuke KOBAYASHI2), Naoyuki AIHARA1), Tamio OHMURO4) and Kinji SHIROTA1,2)*

1)Laboratory of Veterinary Pathology, School of Veterinary Medicine, 2)Reseach Institute of Biosciences and 3)Laboratory of Environmental Pathology, Azabu University, 1–17–71 Fuchinobe, Sagamihara, Kanagawa 252–5201 and 4)Ohmuro Veterinary Clinic, Machida, Tokyo 194–0212, Japan

(Received 28 May 2010/Accepted 20 August 2010/Published online in J-STAGE 3 September 2010)

ABSTRACT. A percutaneous was performed on a 3-year-old female Japanese domestic cat with pleural effusion, mild azotemia, , hypercholesterolemia, and proteinuria. Glomerular lesions included mild diffuse hypercellularity and numerous cap- sular adhesions with segmental sclerosis/hyalinosis of glomerular tufts. Electron microscopy revealed many subendothelial dense depos- its with characteristic outer protrusion of glomerular basement membrane. Diffuse and global granular deposits of IgG and C3 were detected along the capillary walls. Tubulo-interstitial changes were mild at the time of biopsy, but progression of the disease was pre- dicted because of the many capsular adhesions of the glomerular tufts. The cat was fed a prescription diet without any other specific or symptomatic therapy after renal biopsy, and died 43 weeks after the biopsy. At necropsy, extensive tubulo-interstitial fibrosis and mono- nuclear cell infiltration had developed throughout the cortex and outer medulla, and most glomeruli had extensive global sclerosis or obsolescence with less prominent depositions of IgG and C3. KEY WORDS: chronic renal failure, feline, glomerulonephritis, nephrotic syndrome, renal biopsy. J. Vet. Med. Sci. 73(1): 129–132, 2011

Glomerulonephritis is a common renal disease in dogs antibody against feline coronavirus was detected by ELISA and cats and a major cause of chronic renal failure [5]. Uri- in a reference laboratory (IDEXX Laboratories Inc., Tokyo, nalysis and biochemical examinations are useful in Japan). monitoring the disease, but definitive diagnosis and classifi- A percutaneous renal biopsy specimen, performed to con- cation of glomerulonephritis is not possible without histo- firm the presumptive diagnosis of glomerulopathy, was logic examination. The World Health Organization (WHO) fixed in 10% formalin. Paraffin-embedded sections were classification for human glomerular diseases [1] cannot be stained with HE and periodic acid-Schiff (PAS). Immuno- applied to veterinary species unless clinical parameters are histochemistry to detect C3 or IgG was performed on paraf- correlated with pathologic findings through the progression fin sections by the streptavidin-biotin peroxidase method of the disease. We report a case of protein-losing glomerul- (Histofine Kit, Nichirei Corp., Tokyo, Japan) using primary opathy in a cat, in which glomerular, tubular and interstitial antibodies against cat IgG (Kirkegaard & Perry Laborato- lesions progressed considerably over the course of the dis- ries, Inc., Gaithersburg, MD) or cat C3 (Biogenesis, Poole, ease. UK). The chromogen was diaminobenzidine. Sections A 3-year-old female Japanese domestic cat was pre- were counterstained with hematoxylin. sented with mild dyspnea and anorexia. Pleural effusion One biopsy specimen containing more than 10 glomeruli was evident radiographically, and 100 ml of transparent was evaluated. All glomeruli had mild hypercellularity, at fluid was removed by thoracocentesis. chemistry least partially attributed to mesangial hyperplasia. Glomer- indicated mild azotemia, , hypoalbumine- ular tufts were adhered multifocally to Bowman’s capsule mia, and hypercholesterolemia with the following abnormal indicating previous damage with desquamation of glomeru- results (laboratory in parentheses): blood lar epithelial cells (Fig. 1). Focal glomerulosclerosis or nitrogen (BUN), 35.4 mg/dl (10–30 mg/dl); , hyalinosis was noted at many adhesion sites. Thickening of 1.9 mg/dl (0.8–2.0 mg/dl); total protein, 3.8 g/dl (5.5–7.9 g/ the glomerular basement membrane (GBM) was not promi- dl); albumen,1.3 g/dl (2.1–3.4 g/dl); and , 206 nent in the PAS-stained sections. Patchy hypertrophy and mg/dl (90–200 mg/dl) [8]. Urinalysis by reagent strips indi- hyperplasia of the parietal epithelial cells were also noted in cated proteinuria (4+). Blood was negative for feline leuke- the glomeruli. Interstitial mononuclear cell infiltration was mia virus antigen and feline immunodeficiency virus minimal, and interstitial fibrosis was not recognized in the antibody by ELISA (SNAP FIV/FeLV Combo Test, biopsy specimen. By immunohistochemistry, diffuse and IDEXX Laboratories Inc., Westbrook, ME, U.S.A.). No global granular deposition of feline IgG and C3 was detected along the capillary walls (Fig. 2). An epon-embed- *CORRESPONDENCE TO: SHIROTA, K., Laboratory of Veterinary Pathology, Azabu University, 1–17–71 Fuchinobe, Sagamihara, ded block for electron microscopic examination was made Kanagawa 229–8501, Japan. from the paraffin-embedded tissue. With transmission elec- e-mail: [email protected] tron microscopy, many electron-dense deposits were in the 130 J. KAMIIE ET AL.

Fig. 1. Renal cortex; cat. Biopsy specimen. The glomerulus has mesangial expansion with moderate hypercellularity and focal adhesions between the glomerular tuft and Bowman’s capsule (small arrows) with segmental sclerosis (large arrow). PAS. Bar=50 m.

Fig. 3. Transmission electron micrograph. Renal glomerulus; cat. The specimen was prepared from paraffin-embedded biopsy tis- sue. Many subepithelial electron-dense deposits (arrow). Inset: A portion of the capillary wall with subepithelial electron-dense deposits (asterisks) covered by foot process (arrowhead), and the spike-like protrusion of the glomerular basement membrane (arrows). Foot processes of glomerular epithelial cells are fused. C = capillary lumen; U = urinary space. Bar=500 nm.

Fig. 2. Renal cortex; cat. Biopsy specimen. Granular deposits of feline C3 are distributed along the glomerular capillary walls. Streptavidin-biotin peroxidase method, Mayer's hematoxylin counter stain. Bar=50 m. subepithelial regions of glomerular capillary walls (Fig. 3). Thickening of the GBM was obvious but mild; many small projections between the subepithelial dense deposits pro- truded from the GBM. Loss or fusion of foot processes of the glomerular epithelial cells was evident. The cat had been fed a prescription diet (Feline k/d cat Fig. 4. Changes in concentration of (BUN) food, Hill’s-Colgate Japan, Tokyo) for renal disease but no and serum creatinine in a cat with glomerulonephritis during the other specific or symptomatic therapy was provided. Pro- 43 weeks from renal biopsy to death. teinuria was persistent during the first 4 months after the renal biopsy, but was not evaluated afterward. The global sclerosis or obsolescence, but approximately 2% of azotemia progressively increased in severity until the cat’s the 270 glomeruli evaluated had only minimal to mild scle- death 43 weeks after the biopsy (Fig. 4). rosis, but diffuse and global GBM thickening and moth- At necropsy, both kidneys were firm with a fine granular eaten appearance in PAS-stained sections (Fig. 5). With surface. Histologically, renal lesions were more severe than Masson’s trichrome stain, orange to red deposits were scat- at the time of the initial biopsy (Fig. 5). Most glomeruli had tered along capillary walls in nonsclerotic glomeruli. No PROGRESSIVE GLOMERULONEPHRITIS IN A CAT 131

consistent with renal secondary hyperparathyroidism. Histologically, the lesion in the renal biopsy specimen could be classified as membranous nephropathy because there were prominent granular IgG and C3 deposits in the glomeruli and many subepithelial electron-dense deposits with protrusion of GBM around them as described in human [1] as well as feline cases [8, 12]. Segmental capsular adhe- sion was associated with glomerulosclerosis in this case, but was not consistent with focal segmental glomerulosclerosis according to the criteria for classification of human glomer- ular diseases [1]. Segmental sclerosis and capsular adhesion can develop in membranous glomerulonephropathy, espe- cially in the advanced stage in cats [8, 12]. However, marked thickening of GBM suggestive of advanced mem- branous glomerulopathy was not seen in the original biopsy specimen from this case. Ultrastructural changes of GBM in Fig. 5. Renal cortex; cat. Necropsy specimen. Most glomeruli the biopsy specimen resembled those of stage I membranous have global sclerosis. The arrow indicates a glomerulus with relatively mild change. Interstitial cellular infiltration, fibrosis, nephropathy based on WHO classification of human dis- and tubular atrophy or dilatation with hyaline casts or protein- eases [1]. However, in previous studies, sequential ultra- aceous fluid is also prominent. PAS. Bar=100 m. structural staging (I~IV) of the development of electron- dense GBM deposits, as done in human membranous glom- erulopathy, was unrewarding for the disease in dogs and cats [8, 12]. The glomerulopathy in this cat progressed from nephrotic syndrome at the time of renal biopsy to end-stage chronic renal failure in 43 weeks. In human medicine, the classifi- cation of glomerular disease reflects the clinical and histo- pathological characteristics of each category [1]. In cats, only membranous glomerulopathy has been well studied; the morphologic characteristics have prognostic value [7, 8, 12]. In the present case, despite the mildness of GBM lesions, the prognosis was poor because of many irrevers- ible glomerular changes such as capsular adhesions, focal sclerosis/hyalinosis, and extensive GBM deposits. These irreversible glomerular changes might be an indication for treatments to minimize or delay the progression of the dis- ease. Wright et al. [12] stated that the most important factor Fig. 6. Renal cortex; cat. Necropsy specimen. Higher magnifica- tion of the glomerulus marked with an arrow in Fig. 5. There is influencing the outcome of glomerular disease was not sim- diffuse moderate thickening of glomerular basement membrane ply thickening of GBM, but the occurrence of progressive with many spike-like projections (small arrow). The large arrow glomerular sclerosis. The persistent proteinuria in this case indicates proteinaceous material in Bowman’s space. PAS. may have contributed to the development of tubulointersti- Bar=20 m. tial changes; proteinuria has been implicated in tubular injury in human patients as well as in experimental models amyloid deposition was detected with Congo red stain. of protein-losing glomerulonephropathy [2]. Deposition of IgG and C3 was less prominent than in the It is not clear whether the WHO classification of human original biopsy specimen. With electron microscopy, accu- glomerular diseases [1] could be applied to feline diseases, mulation of basement membrane-like matrix and capillary because there are few reports on other types of glomerulone- collapse were observed in the sclerotic or obsolescent glom- phritis in cats [4]. Renal biopsy is a relatively safe proce- eruli. Renal tubules were atrophied; tubular and vascular dure [3, 10]; its use in cases of suspected glomerular disease, walls through the cortex and outer medulla were mineral- especially before azotemia has developed, is needed to ized; the renal interstitium was expanded by fibrosis and establish the clinico-pathological classification of glomeru- mononuclear cell infiltration. These renal changes were lar diseases in animals. The diagnosis should be based on consistent with sclerosing glomerulonephritis with progres- light and electron microscopic and immunohistochemical sion to end-stage kidney. The main extra-renal lesions findings [11]; clinical and histopathological changes of the included cutaneous and pulmonary ; mild hypertro- cases need to be monitored throughout the course of the dis- phy and hyperplasia of the parathyroid glands; and calcifica- ease. 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