Which of the following conditions is a known acquired cause of epilepsy?

Cysticercosis is indeed recognized as an acquired cause of epilepsy. This condition arises from infection with the larvae of the pork tapeworm, Taenia solium, which can lead to the formation of cysts in the central nervous system. When these cysts disrupt normal brain function, they can provoke seizures, leading to the development of epilepsy. The relationship between cysticercosis and epilepsy is well-documented in medical literature, particularly in regions where this parasitic infection is prevalent.

The other conditions listed—neurofibromatosis, Fragile X syndrome, and Down syndrome—are primarily genetic disorders rather than acquired. While they can be associated with seizures and epilepsy, they are not classified as acquired causes of epilepsy. Neurofibromatosis can lead to brain tumors, which may cause seizures, but this is not an acquired infection. Fragile X syndrome and Down syndrome also predispose individuals to various neurological conditions, but they stem from chromosomal abnormalities rather than an external acquired factor.

Thus, in the context of the question, cysticercosis stands out as a clear example of an acquired cause of epilepsy.