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(TMZ) - Rihanna has just cancelled her Grammy performance ... TMZ has learned.

The singer arrived at the Staple's Center but did not walk the red carpet.  She went to rehearsals and left.

Sources connected to the production tell TMZ, Rihanna has been struggling with bronchitis and is on meds. TMZ reported that a doctor on site recommended that she pull the plug on the performance because it could permanently damage her vocal cords.

TMZ sources say Rihanna wanted to perform but reluctantly decided she had to listen to her doctors.  She left Staple's and is going home. She was going to sing "Kiss It Better." She even rehearsed twice but in the end the show just could not go on. 

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