Li Liu, MD
Last Modified: November 1, 2001
Dear OncoLink "Ask the Experts,"
What does toxoplasmosis have to do with brain lymphoma? Are they related?
Li Liu, MD, OncoLink Editorial Assistant, responds:
Thank you for your interest and question.
Toxoplasmosis and primary central nervous system (CNS) lymphoma are unrelated problems which may affect the brain. They are often discussed together because they can both cause "ring-enhancing" brain lesions in immunocompromised patients.
Toxoplasmosis is caused by Toxoplasma gondii, the protozoan parasite that lives in animal feces and soil. Approximately 50% of the general population have been infected with Toxoplasma gondii. In a healthy person, this infection will remain latent. However, the infection can be reactivated in patients with an immunocompromised condition, such as AIDS. Toxoplasmosis in AIDS patients commonly involves the central nervous system (CNS), lung, and eye. A brain biopsy is the only method for definitive diagnosis. A positive toxoplasma antibody only indicates past infection. The standard treatment regimen consists of pyrimethamine, folic acid and sulfadiazine. Response rate is approximately 80 to 90%, in 2 to 21 days.
Primary CNS lymphoma is a malignant lymphoproliferative disease originating in the CNS. It occurs more often in AIDS patients. An MRI of the brain is commonly used in the work-up of these patients. However, MRI sometimes can not tell the difference between CNS toxoplasmosis and CNS lymphoma. For AIDS patients who are debilitated and have low CD4 count empirical anti-toxoplasmosis treatment is sometimes utilized. If the patients do not respond to the treatment in 2-3 weeks, brain radiation with or without biopsy is often recommended.