This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunodeficiency Disorders, Subject name: Pathology
[{'content': 'In an AIDS patient chorioretinitis is typically caused by: \nSelect and explain. \nA. Cytomegalovirus, B. Toxoplasma gondi, C. Cryptococcus neoformans, D. Histoplasma capsulatum', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Cytomegalovirus It may cause disseminated disease, although, more commonly, it affects the eye and gastrointestinal tract. Chorioretinitis was seen in approximately 25% of patients before the advent of HAA, but this has decreased dramatically after the initiation of HAA. Cytomegalovirus retinitis occurs almost exclusively in patients with CD4+ T cell counts less than 50 per microliter. Cryptococcosis Meningitis is the major clinical manifestation of cryptococcosis Toxoplasma gondii It causes encephalitis and is responsible for 50% of all mass lesions in the central nervous system.', 'role': 'assistant'}]