Positive immunostaining for feline infectious peritonitis (FIP) in a Sphinx cat with cutaneous lesions and bilateral panuveitis

Abstract

Feline infectious peritonitis (FIP) is a common, fatal, systemic disease of cats. This case report describes the antemortem diagnosis of FIP in a 2-year-old spayed female Sphinx cat that presented with a bilateral panuveitis and multiple papular cutaneous lesions. Histopathologically, the skin lesions were characterized by perivascular infiltrates of macrophages, neutrophils, with fewer plasma cells, mast cells, and small lymphocytes in the mid- to deep dermis. Immunohistochemistry for intracellular feline coronavirus (FeCoV) antigen demonstrated positive staining in dermal macrophages providing an antemortem diagnosis of a moderate, nodular to diffuse, pyogranulomatous perivascular dermatitis due to FIP infection. Obtaining an antemortem diagnosis of FIP can be a challenge and cutaneous lesions are rare in the disease. Recognition and biopsy of any cutaneous lesions in cats with panuveitis and suspected FIP can help establish an antemortem diagnosis of the disease.

Keywords: feline infectious peritonitis; immunohistochemistry; panuveitis; skin.

Figure 1

Clinical photograph of OD (a) and OS (b) upon initial presentation. Note the hyphema OD and chemosis and prolapse of the third eyelids OU.

Figure 2

Left lateral thoracic wall, cat. Note multiple cutaneous papules.

Figure 3

(a) Histopathology of skin lesion demonstrating nodular inflammatory infiltrate in mid‐ to deep dermis. Hematoxylin and eosin stain, 20× (b) Histopathology of skin lesion demonstrating pyogranulomatous perivascular inflammatory reaction. Hematoxylin and eosin stain, 600× (c) Immunohistochemical staining of skin lesion. Macrophages within the inflammatory infiltrate express feline coronavirus (FCoV) antigen. Streptavidin‐biotin complex technique following protease pretreatment, 600×.