Case Presentation: A 65 year old male presented to our emergency department with rectal pain. One month prior to presentation, he had a perirectal abscess which was incised and drained. The patient had persistent rectal pain post surgery. Two weeks prior to admission, the rectal pain increased. He went to see his primary care physician who subsequently sent the patient to the emergency department.The patient’s past medical history is significant for chronic kidney disease status post renal transplant one year prior. Since transplant, he has had no significant events and has been on maintenance immunosuppression of mycophenolate mofetil, prednisone, and tacrolimus. His family history was negative for cancer. The patient is retired and on disability and lives with his wife. He normally ambulates with a cane. He denies tobacco, alcohol, and recreational drugs. On physical exam, a 5 cm tender erythematous indurated fluctuant mass was noted on the right perirectal area with purulent drainage. The rest of the physical exam was insignificant. A CT of the abdomen showed asymmetric thickening of the right rectal wall. The patient had a tru-cut biopsy of the right rectal mass. Final pathological diagnosis revealed perirectal collection of macrophages with Michaelis-Gutmann bodies, consistent with rectal malakoplakia.The patient had surgical resection of the mass with concurrent ciprofloxacin 500mg daily for 6 months. Immunosuppression was decreased during this treatment regimen. The patient is doing well 7 months after surgical resection without symptoms of disease.

Discussion: Malakoplakia (“soft plaque” in greek) is a rare granulomatous disease first described in 1902. Since then, approximately 450 cases have been reported in the English literature, with over 75% involving the genitourinary tract and less than 10% involving the gastrointestinal tract. GI malakoplakia, as seen in our patient, is extremely rare with less than 50 reported cases in the English literature. Lesions usually present as soft yellowish plaques or nodules. Patients are typically immunosuppressed. Malakoplakia results from inadequate macrophage destruction of bacteria secondary to defective phagolysosomal activity. The partially digested bacteria accumulate in the macrophages, leading to deposition of calcium and iron on the residual bacterial glycolipid. This results in basophilic inclusion structures, or Michaelis-Gutmann bodies, which are pathognomonic for malakoplakia and required for diagnosis. Treatment of malakoplakia includes a combination of surgery, antibiotics, and decrease/cessation of immunosuppressive therapy. Appropriate antibiotics include those that concentrate in macrophages (i.e. quinolones, TMP-SMX). Our patient had surgical resection with concurrent ciprofloxacin therapy. At the time of writing this report, lesions almost disappeared as of 7 months after presentation.

Conclusions: Malakoplakia is a rare granulomatous disease that may present as a rectal mass and be misdiagnosed as an abscess or tumor. Diagnosis requires biopsy demonstrating Michaelis-Gutmann bodies.