Successful treatment of vaginal malakoplakia in a young cat

Abstract

Case summary: A 3-year-old, female, spayed, domestic shorthair cat presented for dysuria and haematuria, unresponsive to antibiotic treatment. A small, fleshy, erythematous mass protruded from the vaginal vault. Ultrasound identified a vaginal mass effect with mixed echogenicity measuring in excess of 3 cm. Vaginoscopy confirmed an extensive, fleshy, irregular mass that was characterised histologically as pyogranulomatous vaginitis, with periodic acid-Schiff-positive macrophages containing gram-negative bacteria. Fluorescence in situ hybridisation analysis demonstrated invasive intracellular Escherichia coli. Vaginal malakoplakia was diagnosed. Tissue culture and antimicrobial susceptibility of E coli was used to guide treatment. A 6 week course of enrofloxacin 5 mg/kg q24h resulted in complete resolution of the mass and clinical signs.

Relevance and novel information: Malakoplakia is a rare chronic inflammatory condition that has been previously reported in the bladder of two cats. The pathogenesis of malakoplakia is thought to involve ineffective killing of bacteria (eg. E coli), similar to granulomatous colitis in Boxers and French Bulldogs. The literature on malakoplakia in cats is sparse. This is the first reported feline case with vaginal involvement, intracellular E coli and successful treatment with a fluoroquinolone. Malakoplakia is an important, non-neoplastic differential diagnosis when a mass is identified in the urogenital system of a young cat.

Figure 1

Longitudinal view of the vaginal mass, with calipers demonstrating the craniocaudal extent of the lesion. White arrows indicate the location of the lesion

Figure 2

Pyogranulomatous inflammation composed predominantly of neutrophils and macrophages. Faint basophilic objects consistent with bacterial rods are visible in macrophages (see inset, indicated by white arrow). Haematoxylin and eosin, × 50

Figure 3

Macrophages contain variably prominent periodic acid–Schiff-positive granules (PAS, × 50)

Figure 4

Macrophages contain gram-negative bacterial rods (see inset, indicated by white arrow). Gram stain, × 100

Figure 5

Fluorescence in situ hybridisation (FISH) analysis of vaginal mucosa. Eubacterial FISH revealed multifocal clusters of intracellular rods within the vaginal mucosa (arrows). These bacteria hybridised with an Escherichia coli/Shigella species probe (inset). Bacteria (Cy3) are red/orange. Nuclei (4′,6-diamidino-2-phenylindole) are blue