New York CNN  —  UnitedHealth Group, one of America’s biggest corporations and a member of the exclusive Dow Jones Industrial Average, is suddenly unraveling. The crisis engulfing UnitedHealth hit a crescendo this week when CEO Andrew Witty stepped down abruptly for “personal reasons.” UnitedHealth also swiftly abandoned its financial guidance , blaming skyrocketing medical costs. And then The Wall Street Journal dropped the hammer, revealing that UnitedHealth is under federal criminal