What condition is indicated by ring-enhancing lesions on a CT scan in an HIV patient?

In patients with HIV, ring-enhancing lesions on a CT scan are most commonly associated with Toxoplasmosis. This parasitic infection is caused by Toxoplasma gondii, which can reactivate in immunocompromised individuals, such as those with HIV/AIDS. The lesions typically appear as multiple ring-enhancing areas due to the inflammatory response surrounding necrotic tissue caused by the infection.

Toxoplasmosis is particularly noted for causing these distinctive imaging findings, often in a context where a patient’s CD4 count is significantly low, predisposing them to opportunistic infections. In most cases, these lesions are located in the basal ganglia and corticomedullary junction.

While primary CNS lymphoma can also produce ring-enhancing lesions, it tends to present as single, rather than multiple lesions, and has different imaging characteristics. Brain abscesses can appear similar but typically arise from bacterial infections and are often associated with a history of head trauma or other predisposing factors. Neurocysticercosis, caused by the larval form of the pork tapeworm, generally presents with cystic lesions rather than the classic ring-enhancing appearance seen in Toxoplasmosis.

In summary, the presence of ring-enhancing lesions in