Toxoplasma Gondi

Epidemiology and Etiology:

• protozoan
• acquisition:
• Oocyst-shedding cats
• Eating cyst-ridden, undercooked meat
• AIDS patients - one of the most common causes of neurologic symptoms and morbidity in patients with AIDS
• Neonates (TORCH infection)

Common sites:

• Cerebral cortex (gray-white junction)
• Deep gray nuclei
• Chorioretinitis

Gross features:

• multiple frequently
• necrotic

Histologic features:

• necrotizing encephalitis
• central necrosis
• surrounding acute and chronic inflammation
• macrophages
• microglial nodules
• vascular proliferation
• May see intimal proliferation
• may see vasculitis with fibrinoid necrosis and thrombosis
• organisms found at the periphery of necrosis
• free tachyzoites
• encysted bradyzoites
• after treatment:
• large, well-demarcated areas of coagulation necrosis
• surrounding lipid-laden macrophages
• cysts and free tachyzoites reduced in number or absent
• dystrophic calcification

Immunophenotype:

Marker:	Sensitivity:	Specificity:
Specific immuno available

Molecular features:

Other features:

• subacute onset (1-2wks)
• ring-enhancing lesions on CT and MRI

References:

• Robbins 2005
• Essentials of AP 2006