Horizon Group Management LLC filed a lawsuit Tuesday claiming Amanda Bonnen of Chicago defamed the company in a May message on Twitter.
The microblogging service lets account holders give status updates in 140 characters or less.
Horizon attorney Jeff Michael says that on May 12, Bonnen messaged another accountholder: "Who said sleeping in a moldy apartment was bad for you? Horizon realty thinks it's OK."
The lawsuit, which seeks $50,000, claims that because Bonnen's Twitter account was public, her comment was published "throughout the world."
Telephone calls to Bonnen and her attorneys were not immediately returned. Her Twitter account has been deactivated.