Legendary Australian rock band AC/DC's founding guitarist Malcolm Young will not be returning to the line-up for its new record, Rock or Bust, because he's suffering from dementia.
"Malcolm is suffering from dementia and the family thanks you for respecting their privacy," his family said in a statement, according to Rolling Stone magazine.
The high-voltage group, one of the highest grossing bands of all times, was founded by Malcolm and his brother Angus in Sydney in 1973 and went on to sell more than 200 million albums, the ABC reports.
In announcing a new record, Rock or Bust, last week, the band confirmed 61-year-old Young would not be returning to the line-up.
He had taken a break earlier this year due to unspecified ill health.
"Unfortunately, due to the nature of Malcolm's condition, he will not be returning to the band," AC/DC said on its website at the time.
"AC/DC will undertake a world tour in support of Rock or Bust in 2015."
The band said Stevie Young, the nephew of Angus and Malcolm Young, would perform on the album and join them on the tour.
The band has withstood the loss of key members in the past, in particular when lead singer Bon Scott died in 1980.
AC/DC most recently completed a 20-month world tour in 2010 in support of its 2008 album Black Ice. Rock or Bust is due to be released on December 2.