Silent Colonic Malakoplakia in a Living-Donor Kidney Transplant Recipient Diagnosed during Annual Medical Examination
A 55-year-old female visited the outpatient clinic of the Samsung Medical Center for routine cancer surveillance in May 2011. The patient received a living-donor kidney transplant eleven years ago for end-stage renal disease secondary to IgA nephropathy at Kyunghee University Medical Center. She was on stable doses of immunosuppressive drugs, including prednisone, tacrolimus, and mycophenolate, at the time of the current visit. She had no rejection or other complications of transplantation to date, and was asymptomatic. Her routine cancer surveillance included complete blood counts, a liver function test, abdominal sonogram, gynecologic exam, upper gastrointestinal endoscopy, and colonoscopy. Results were all unremarkable, except or the colonoscopy findings. The colonoscopy revealed several depressed flat lesions and elevated polyps, which were 0.3 to 0.4 cm in size and accompanied by whitish exudates (). The differential diagnosis for the endoscopic lesions included graft-versus-host disease, cytomegalovirus colitis, and amoebiasis. Multiple biopsies were obtained from several sites. Microscopic findings from all biopsy materials revealed the infiltration of many histiocytes with ample granular eosinophilic cytoplasm with some lymphocytes and plasma cells. Many histiocytes had the characteristic morphology described as Michaelis-Gutmann bodies (): one or several round basophilic structures of approximately 1 to 10 µm in size, with some being laminated, some appearing homogeneous, and others having a dense central core with a targetoid appearance. These Michaelis-Gutmann bodies were positively stained on von Kossa stain, and were diagnostic for malakoplakia (). The patient did not receive any treatment. After 1 year, she underwent an annual health examination at Samsung Medical Center in May 2012. She still did not have any symptoms, and had been taking immune suppressive medication. This time she did not receive a colonoscopy. Aspects of the check-up showed results within normal ranges.