Abdominal Malakoplakia Secondary to Disseminated Mycobacterium Avium Complex after Lung Transplant

Abstract

Introduction Malakoplakia is a rare granulomatous inflammation in response to a bacterial infection. It is incited by incomplete macrophagic degradation of bacteria. The presence of these remnant phagosomes on pathology is considered pathognomonic for malakoplakia and known as Michaelis-Gutmann bodies (MGB). There are few case reports describing malakoplakia after lung transplant and none of which describe disseminated Mycobacterium avium Complex (MAC) induced malakoplakia. Case Report A 60-year-old female, with history of hypogammaglobulinemia and double lung transplant for bronchiectasis, presented with abdominal pain 6 months after transplant. She was diagnosed with acute diverticulitis and treated with IV antibiotics. Subsequently, she was readmitted with perforated diverticulum and a new complex phlegmon by CT imaging. In spite of antibiotics, the phlegmon enlarged. She underwent exploratory laparotomy that revealed a dense abdominal mass. The histopathologic exam of this mass showed MGB, by PAS and Von Kossa stains, diagnostic of malakoplakia. Tissue cultures grew VRE and E. coli, but intra-peritoneal fluid cultures grew MAC. However, tissue PCR and blood cultures were negative. MAC was deemed a contaminant and no treatment was rendered. The malakoplakia was thought to be secondary to VRE and E. Coli infection for which she was treated appropriately, and immunosuppression was lowered. She was readmitted with ongoing pain, and CT of abdomen showed further increase in size of mass. Repeat AFB blood cultures were positive for MAC. She was started on MAC therapy with clinical and radiographic improvement. Summary Since differential of malakoplakia could include malignancy, it is imperative to obtain tissue sampling. In this case, despite early sampling, diagnosis was delayed due to the uncertainty surrounding the isolated growth of MAC with above negative testing. This discordance could be explained by only a 70% sensitivity of PCR with negative AFB smear. Notably, false negatives may occur if organisms are present in low numbers. Patient had positive AFB blood cultures with negative respiratory cultures suggesting an extrapulmonary etiology of disseminated MAC. This in combination with continued growth of the mass despite culture directed antibiotics and improvement following initiation of MAC therapy supports the diagnosis of MAC induced malakoplakia.