The Hornets said in a press released there is no timetable for Clifford's return. The team did not provide any additional details on the situation "out of respect for Clifford's privacy."
The 56-year-old Clifford missed Monday's victory against the Orlando Magic for what the team said was an illness. He also was not at Tuesday's practice.
This is the Clifford's fifth season with the Hornets. He missed some time in his first season after experiencing chest pains.
Hornets associate head coach Stephen Silas will serve as acting head coach during Clifford's absence.
The Hornets are 9-13 this season and host the Golden State Warriors on Wednesday night.