What Happened To Old Biff In Back To The Future 2?

When the original model of Biff Tannen returns in 2015 following an adventure in time Back to the Future Part II

He is sick without explanation, with only one deleted sequence will reveal what happened to the old Biff. 

Back to the Future Part II is the sequel of the Back to the Future trilogy that follows 

what happens to Marty McFly and Doc Brown who travel through time via the DeLorean the time machine. 

The antagonist in the series is Biff Tannen which is who is played by Thomas F. Wilson. 

The film Back to the Future, Biff is introduced in 1985 as an older man who pushes on Marty's father George. 

In 1955 the year he's a high-school bully who mocks George and scolds Marty's wife, Lorraine.