Why Did Kelly Osbourne Have a Seizure?

Kelly Osbourne remains hospitalized as her doctors try to figure out what caused her to have a seizure on the set of Fashion Police Thursday.

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Osbourne tweeted a picture of herself hooked up to an IV Saturday with the caption, "Thank U all 4 UR beautiful well wishes. yes I did have a seizure they are just trying to figure out why?"

One possibility is that the commentator may be epileptic, sources tell TMZ. No official diagnosis has been made, but the incident may have been more serious than doctors initially thought, and Osbourne remains on anti-seizure medication, according to the report.