A mysterious patient listed as "John Doe" faces the possibility of death alone at UC Irvine Medical Center because his friends and relatives may be afraid to see him, an official said. The man, who understands Spanish, may be an illegal immigrant and acquaintances may fear arrest if they try to contact him, said Julie Christina, a public safety officer for UC Irvine. The man, about 20, was brought unconscious to the medical center Jan. 6, and because of subsequent throat surgery cannot tell authorities his name, she said. "A woman brought him here in a car . . . but she never came back," Christina said. He underwent surgery to relieve pressure on his brain, and on Monday is to have an operation to repair a brain aneurysm, a potentially fatal condition caused by a weakened blood vessel in the brain. Relatives who wish to contact him will not be turned over to immigration authorities, Christina said.