Hidden in Granulomatous Inflammation: Histopathologic Challenges of Cutaneous Balamuthia mandrillaris Infection—A Canadian Case Report

Balamuthia mandrillaris is a rare cause of cutaneous amebiasis that can progress to central nervous system infection, almost always resulting in death. It is a free-living, opportunistic ameba found globally in dust, soil, and freshwater that can infect people of all ages regardless of the status of the host immune system. Herein, we report a case of B. mandrillaris infection in Canada in an 83-year-old man presenting to the hospital with altered mental status and a chronic wound of 4-year duration. A skin biopsy of the chronic wound revealed extensive dermal granulomatous and mixed inflammatory infiltrate with abundant multinucleated giant cells. Inspection of multiple level sections revealed structures concerning for amebic trophozoites. After the patient's death, lesional tissue from the skin and brain was sent to the Centers for Disease Control (CDC) for further subtyping, which confirmed B. mandrillaris as the causative organism. This case raises awareness for this organism as a possible cause of cutaneous infections and highlights the necessity for dermatopathologists and pathologists alike to have a heightened suspicion for amebic infections when non-specific granulomatous inflammation is identified in the skin.