Aretha Franklin has canceled a pair of upcoming appearances to undergo treatment for an undisclosed condition.

The soul icon was set to perform in Chicago, Illinois, on Monday with members of the Chicago Symphony Orchestra (CSO) and at the Foxwoods Resort & Casino in Ledyard, Connecticut, on May 26, but her doctor recommended that she cancel the shows for treatment of whatever is ailing her.

Franklin canceled shows in 2010 to have a tumor removed -- something she kept secret for two years before revealing it in 2012 -- and she has also battled issues with her legs and feet in the past. She was also forced to pull out of her performance at late singer Whitney Houston's funeral last year.

Janelle Monae is set to replace her at the Chicago show, which celebrates the city's 24th annual Corporate Night.

Further details of the singer's illness haven't been released.