Singer Johnny Cash has Parkinson's disease October 27 Web posted at: 9:57 p.m. EST (0257 GMT) NEW YORK (CNN) - Country singer Johnny Cash announced Monday through his publicist that he has developed Parkinson's disease. The publicist, promoting "Cash: The Autobiography," released a statement saying the singer has cancelled his national book-promotion tour because the disease has progressed. "Johnny and his wife, June Carter Cash, are sorry to have to postpone personal appearances," the statement said. "Johnny feels confident that once the Parkinson's is medically stabilized, he can resume his normal work schedule," Cash's manager, Lou Robin, said through the statement. An upcoming concert tour also had to be cancelled because of the 65-year-old singer's worsening medical condition, according to an ABC News radio report.