Colonic Malakoplakia With an Adenomatous Appearance on Magnification Endoscopy: A Case Report

Malakoplakia is a rare chronic granulomatous disease associated with impaired macrophage phagocytosis of bacteria. Because colonic malakoplakia presents with varied endoscopic appearances, its characteristic features have not been clearly defined, and differentiation from colorectal neoplasms during endoscopy may be difficult. We report a case of colonic malakoplakia with adenomatous features evaluated using magnifying narrow-band imaging (NBI). A patient receiving hemodialysis and corticosteroid therapy for immunoglobulin A nephropathy underwent total colonoscopy after a positive fecal immunochemical test. Two reddish polyps were identified in the ascending colon. Magnifying NBI showed either absent or regular surface patterns with fine, thread-like vessels, along with areas resembling adenomatous changes. Although malignant features were not observed, a definitive diagnosis could not be established endoscopically. Consequently, both lesions were resected using cold snare polypectomy. Histopathological examination revealed a granulation tissue-like inflammatory lesion composed of histiocytes containing Michaelis-Gutmann bodies in the lamina propria and submucosa, leading to a diagnosis of malakoplakia. Based on this diagnosis, a surveillance colonoscopy was scheduled for 1 year later.