"The X-Files" star Gillian Anderson was honored at a Senate lunch yesterday for her work in the fight against neurofibromatosis, a genetic order that affects 100,000 Americans, including her 19-year-old brother, Aaron. "It's a little-known but relatively common disease," Anderson, 31, told The Washington Post. "And it's often misdiagnosed." The disfiguring disorder causes tumors to grow on nerves all over the body, and her brother was diagnosed at the age of three. "Right now he seems to have one of the lighter cases," she said. "But the thing about NF is that it is a progressive disease." Anderson has raised about $250,000 for the nonprofit Neurofibromatosis Inc., reports the Post, mostly by auctioning off "X-Files" memorabilia on the Web.