Malakoplakia of the Bladder in a 4-Month-Old Puppy

Abstract

A 4 mo old female Staffordshire bull terrier puppy was presented with chronic Escherichia coli cystitis. Ultrasound and cystoscopic examination revealed innumerable, intraluminal, finger-like proliferations arising from the dorsal urinary bladder (UB) wall. Histological examination of mucosal biopsies obtained by cystoscopy was suggestive of granulomatous cystitis. The proliferative lesions were removed surgically and submitted for histological examination. The UB submucosa was heavily infiltrated by macrophages with periodic acid-Schiff-positive cytoplasm exhibiting rare Michaelis-Gutmann bodies, leading to the diagnosis of malakoplakia. The puppy was prescribed with sulfamethoxazole-trimethoprim. The urinary signs disappeared despite the persistent UB wall thickening revealed by abdominal ultrasound. Urine culture performed during the ninth week of treatment showed a persistent infection by E coli resistant to sulfamethoxazole-trimethoprim. The dog was switched to doxycycline but was then lost to follow-up. Malakoplakia is a chronic granulomatous inflammation well documented in humans. Its pathophysiology is not fully understood, but bacterial infection, immunodepression, and a defective lysosomal function may lead to the intracytoplasmic accumulation of partially degraded bacteria that can subsequently mineralize to form the Michaelis-Gutmann bodies. Malakoplakia should be suspected when UB mass lesions are identified in a young dog with bacterial cystitis.