Renal malakoplakia with invasion of the liver and diaphragm: a patient case and literature review

Background

Malakoplakia, Latin for ‘soft plaque’, is a chronic and rare inflammatory disorder that most commonly presents in immunocompromised patients. First delineated in the early 20th century by Michaelis and Gutmann, the pathogenesis is still not well understood.1 This inflammatory reaction is thought to occur due to phagocyte function defects in response to bacterial infections. Primarily, the bacterial instigator is Escherichia coli as coliform bacteria have been found in nearly 90% of patients, more rarely the Proteus sp has been found as well.2 3 It has been described in numerous case reports but occurs most commonly in the genitourinary (GU) tract.1 On microscopic examination, this disorder is characterised by ‘von Hansemann cells’ or sheets of foamy macrophages that present along with ‘Michaelis-Gutmann bodies’, which are round basophilic scattered intracytoplasmic inclusions.1

Since the 1902 description of malakoplakia in a patient’s bladder, there have been over 400 case descriptions ranging from the most common GU occurrences to those in the pancreas, thyroid gland, lung, bone, skin and brain.1 This disease is more common in men and presents at a median age of 53 years. The large majority of patients are immunodeficient due to causes such as HIV infection, neoplasia and kidney transplantation; there have been reported cases in healthy patients.4 The most common symptom of malakoplakia is a recurring urinary tract infection (UTI), haematuria or renal failure occurring at presentation.5 Typically, E. coli would be grown in urine cultures or evidence could be seen on cystoscopy.

The clinical picture of those diagnosed with malakoplakia widely varies, and diagnosis is usually made after scrupulous workup. Culture, histopathology and 18-fluorodeoxyglucose positron emission tomography scan are critical to establish diagnosis and determine need for follow-up.6 Additionally, the same characteristics that are pathognomonic for malakoplakia, Michaelis-Gutmann bodies, are why the von Kossa calcium stain is so critical. The von Kossa stain is a widely used histological technique which detects the presence of abnormal calcium deposits. This occurs from the breakdown of calcium salts into silver salts. Once placed under an ultraviolet source, the silver phosphates degrade and allow for counterstaining with nuclear red. In malakoplakia, the histiocytic inclusions stain positive for calcium, an important finding in malakoplakia.

The prognosis is positive as death has occurred very infrequently and individuals are cured in over 80% of cases. The primary treatment has been antibiotics with quinolones and trimethoprim/sulfamethoxazole with other modifying therapies including immunosuppressant discontinuation or bethanechol administration.3 7 Importantly, these outcomes are derived from the common malakoplakia which is often benign. Here, we report a case of malakoplakia with unusual invasive features. The diagnostic workup, including specific pathological characteristics, and the management of the case are described.

Case presentation

A female patient in her 50s had a history of tobacco use for over 30 years and no known immunodeficient conditions. She was previously admitted to the hospital 4 years prior for flank pain, haematuria and dysuria. Workup revealed a benign renal polyp with concurrent UTI. After that, she experienced intermittent haematuria every 2–3 months, and each episode would receive an antibiotic regimen from an outpatient physician without a standard UTI workup. Her last episode began 5 days prior to admission. She experienced haematuria and right upper abdominal pain with subsequent spread of pain to the right anterior groin and right flank.

Investigations

Her creatinine level was 0.6 mg/dL (estimated glomerular filtration rate was >60 mL/min/1.73 m²) and her white cell count was 8500/µL (neutrophil count was 82.0%). Urine culture grew E. coli organisms.

The heterogeneously enhancing mass (8.1×5.4×8.0 cm in size) at the right upper pole with extension to the renal pelvis causing renal pelvis dilation and extension into the diaphragm superiorly was noted on the enhanced MRI of the abdomen (figures 1 and 2); rupture of the right upper pole calyx with mixture of cystic and solid lesion within the perirenal fat and liver was noted (6.6×3.2 cm in size).

Differential diagnosis

This was suspected to be an infected urinoma with tumour involvement and biopsy was performed. Biopsy for the lesion was performed, and pathological analysis revealed numerous macrophages with basophilic and eosinophilic granular cytoplasm containing intracellular and extracellular bacteria mixed with acute inflammatory cells and nearby fibrotic tissue containing abundant plasma cells and lymphoid cells (figure 3). By special von Kossa stains, rare Michaelis-Gutmann bodies were identified as well as many eosinophilic globules (figure 4). These findings were consistent with malakoplakia.

Treatment

Radical nephrectomy was indicated due to the suspected permanent renal damage and concern for invasive damage to other tissues. After discussing with the patient and her family, right robotic radical nephrectomy with adrenal sparing was performed. The tumour was inflammatory and dissected off the liver capsule and diaphragm. The final pathology report was malakoplakia; the Gerota fascia was congested. The specimen weighed 495 g and measured 17.0×10.0×7.0 cm. The mass was 8.0×7.5×6.5 cm in the superior pole of the kidney and contained a cyst measuring 2 cm, filled with fibrinopurulent material (figure 2). Within the mass, diffuse histiocytic inflammation (highlighted by immunostaining CD68) was noted, with the histiocytes containing eosinophilic cytoplasm and round intracytoplasmic inclusions consistent with Michaelis-Gutmann bodies (figure 3).

Outcome and follow-up

After the surgical treatment, her clinical recovery and laboratory outcomes were satisfactory, and she no longer suffered from urosepsis. There was no adverse event or recurrence noted on follow-up images. The patient remained alive and free of disease 6 months after treatment (figure 5).