A 30-year-old immunocompromised woman living in the northeastern United States was found unresponsive by her boyfriend. She had never traveled outside of the area and worked as a retail clerk Autopsy reveals the following microscopic findings (see figures).
The correct answer is ...
All four of the following organisms can involve myocardium but can be distinguished based on morphology.
Trichinella spiralis larvae are able to be distinguished on low-power microscopic examination, but distinction between Toxoplasma, Trypanosoma, and Sarcocystis requires high-power examination under oil.
Sarcocystis hominis have a more tubular appearance, and Trypanosoma cruzi amastigotes are remarkable for the presence of kinetoplasts, a rod-shaped structure situated close to the nucleus.
Toxoplasma gondii can be seen in the form of encysted bradyzoites as well as individual tachyzoites. This case is an example of a single cyst within myocardium, containing organisms morphologically consistent with Toxoplasma gondii.
Michael Kritselis, D.O.
Fellow, Cardiovascular Pathology
Melanie Bois, M.D.
Consultant, Anatomic Pathology
Associate Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science