Granulomatous nephritis consistent with malakoplakia in a cynomolgus monkey

A case of canine intestinal malakoplakia

Malakoplakia is a rare chronic granulomatous disease usually affecting the urinary bladder and other locations. In humans, the gastrointestinal tract is the second most common location but there are no reports of intestinal malakoplakia in animals. A 10-month-old female French Bulldog was presented with chronic haemorrhagic diarrhoea and anorexia with normochromic-normocytic anaemia and hypoalbuminaemia. Grossly, there was mucosal thickening and ulceration of the caecum, colon and rectum. Microscopically, transmural sheets of foamy macrophages were seen in these tissues. Macrophages were periodic acid-Schiff, vimentin and ionized calcium-binding adaptor molecule 1 positive and contained von Kossa- and Prussian blue-positive Michaelis-Gutmann bodies. Giemsa staining revealed rod-shaped bacterial colonies and fluorescence in-situ hybridization demonstrated Escherichia coli within macrophages. This is the first reported case of intestinal malakoplakia in domestic animals. Pathological features of intestinal malakoplakia share many similarities with ulcerative histiocytic colitis in dogs but it is unclear if they are different forms of the same pathological process or distinct entities.

Malakoplakia of the urinary bladder in a young French Bulldog

CASE DESCRIPTION

A 4-month-old 5.9-kg sexually intact female French Bulldog was presented because of recurrent urinary tract infections in combination with pollakiuria, hematuria, and urinary incontinence.

CLINICAL FINDINGS

A diagnosis of malakoplakia was made on the basis of results of hematologic and serum biochemical testing, abdominal ultrasonography, bacterial culture, and cystoscopic biopsies of the urinary bladder wall. Biopsy samples were sent for routine histologic examination and fluorescence in situ hybridization to confirm the presence of intracellular and subendothelial bacteria.

TREATMENT AND OUTCOME

Treatment with enrofloxacin was started after the diagnosis of malakoplakia was confirmed. During treatment, polypoid changes in the urinary bladder decreased dramatically but did not disappear. On follow-up ultrasonography after 12 weeks of treatment, marked improvement was visible and results of repeated bacterial culture and fluorescence in situ hybridization of bladder wall samples were negative. The patient was free from clinical signs and had an ultrasonographically normal urinary bladder 59 weeks after antimicrobial treatment was discontinued.

CLINICAL RELEVANCE

Malakoplakia, a granulomatous disease characterized by impaired histiocytes that are unable to completely digest phagocytized bacteria, is a very rare disease in dogs, but early suspicion of the condition is essential to allow timely diagnosis and avoid disease progression and the need for prolonged treatment. Malakoplakia should be considered in young dogs with chronic urinary tract infections; the diagnosis can be made through a combination of histologic examination and fluorescence in situ hybridization of bladder wall biopsy samples.

Malakoplakia in the Urinary Bladder of 4 Puppies

Malakoplakia in humans most often affects the urinary bladder and is characterized by inflammation with von Hansemann-type macrophages, with or without Michaelis-Gutmann bodies, and is frequently associated with Escherichia coli infection. We describe the microscopic features of malakoplakia in the urinary bladder of 4 puppies. In all cases, the lamina propria of the urinary bladder was markedly expanded by sheets of large, round to polygonal macrophages with intracytoplasmic, periodic acid-Schiff-positive granules and granular inclusions, and rare Prussian blue-positive inclusions. Macrophages were positive for CD18 and Iba1. In 2 cases, Michaelis-Gutmann bodies were detected with hematoxylin and eosin stain and were best demonstrated with von Kossa stain. E. coli infection was confirmed in 2 cases with bacterial culture or polymerase chain reaction (PCR) and sequencing of the bacterial 16S ribosomal RNA gene. Transmission electron microscopy of one case demonstrated macrophages with abundant lysosomes, phagolysosomes, and rod-shaped bacteria. Microscopic features were similar to human cases of malakoplakia. In dogs, the light microscopic characteristics of malakoplakia closely resemble granular cell tumors and histiocytic ulcerative colitis.

Successful treatment of vaginal malakoplakia in a young cat

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.