Granulomatous nephritis consistent with malakoplakia in a cynomolgus monkey

Area of Science:

• Veterinary Pathology
• Primate Medicine
• Inflammatory Diseases

Background:

• Malakoplakia is a rare chronic granulomatous inflammation typically affecting the urinary tract in humans.
• It is characterized by the presence of specific cellular inclusions and inflammatory infiltrates.

Purpose of the Study:

• To document and characterize a case of granulomatous nephritis consistent with malakoplakia in a non-human primate.
• To contribute to the understanding of malakoplakia in mammalian species beyond humans.

Main Methods:

• Gross examination of the affected kidney.
• Histopathological analysis including Periodic Acid-Schiff (PAS) and iron staining.
• Ultrastructural examination using electron microscopy.

Main Results:

• The kidney exhibited marked enlargement and adherence to surrounding organs.
• Histology revealed diffuse interstitial infiltration by histiocytes (von Hansemann cells) with characteristic cytoplasmic inclusions.
• Electron microscopy confirmed abundant lysosomes and phagolysosomes, though Michaelis-Gutmann bodies were not definitively identified.

Conclusions:

• The findings support a diagnosis of granulomatous nephritis consistent with early malakoplakia in the cynomolgus monkey.
• This represents the first reported case of a renal lesion resembling malakoplakia in a monkey, expanding its known mammalian hosts.