Thompson Square cancelled a string of tour dates because Keifer Thompson is suffering from a "very serious vocal condition."

The duo, composed of Keifer and his wife Shawna, cancelled Thursday night's headlining show in Glen Allen, Virginia and four of their shows opening for Luke Bryan.

Keifer's vocal condition has been an issue for several weeks.  In a letter to fans he wrote:

"I was urged by doctors to cancel Thompson Square's appearances and go on complete vocal rest several weeks ago; however, neither Shawna nor I wanted to disappoint our fans, which we love and respect dearly. So we chose to continue performing our scheduled shows while I remained completely silent offstage in an effort to heal. Unfortunately, at this time, I have been ordered by doctors to take the next step and to cancel this weekend’s shows in an effort to heal internally."

Thompson Square is scheduled to play Charlotte with Luke Bryan on July 12th.