An HIV-positive patient presents with fever, headache, and right hemiparesis, with MRI showing 6 ring-enhancing lesions. What is the treatment of choice?

The treatment of choice for a patient with HIV presenting with neurological symptoms and MRI findings of multiple ring-enhancing lesions is sulfadiazine and pyrimethamine. These lesions are most commonly associated with toxoplasmosis, which occurs frequently in immunocompromised patients, such as those with HIV/AIDS.

Sulfadiazine is a sulfonamide antibiotic that acts against the parasite Toxoplasma gondii, while pyrimethamine functions as a folate antagonist that inhibits dihydrofolate reductase, further enhancing the efficacy of the treatment against the parasite. This combination is specifically recommended for the management of toxoplasmosis because it targets the organism effectively and helps control the associated inflammation.

In cases of CNS toxoplasmosis, it is essential to initiate treatment promptly due to the risk of significant morbidity and the potential for rapidly worsening symptoms. Supporting this choice is also the common clinical practice guidelines which endorse sulfadiazine and pyrimethamine as first-line therapy for this condition.

The other treatment options listed have specific indications but do not address the underlying infection. Trimethoprim-sulfamethoxazole is primarily used for prophylaxis against Pneumocystis pneumonia rather than treating toxoplasmosis. Radiation therapy