We report a patient who developed reactivated toxoplasmic encephalitis due to human immunodeficiency (HIV)-associated immune compromise, resulting in a breakdown of the balance between the host immunity and toxoplasma cyst. Through detailed pathological analysis, spilling of tachyzoites from the ruptured wall of toxoplasma cyst can be identified. It was also proved that Toxoplasma gondii would infect endothelial cells of blood vessels, leading to vasculitis and brain ischemic necrosis. By transmission electron microscope (TEM), apical complex of the parasite can be identified, as well as tachyzoites in rapid reproduction through fission. Rhoptry, a club-shaped specialized organelle, which is characteristic of the motile stages of Apicomplexa protozoans, was also identified. The prevention of toxoplasma infection is still an issue to be emphasized in public health. This article is special in its pathophysiology-based description of the morphology. 'Form ever follows function' is a famous quote from the architect Louis Sullivan. In this case report, we make effort to depict a pathophysiology-based or a 'form-function correlation' interpretation of the histopathological findings by light microscope, IHC and ultrastructural examination. We believe such an approach should also be included in the daily pathology resident training program.
Keywords: Electron microscope; Toxoplasma gondii; encephalitis; toxoplasmosis.