Well, a rare neurological disorder that affects one in a million people, leading to muscle stiffness and painful spasms, even at the slightest over-exposure to touch, noise, and emotional distress. But what hurt her the most was that the disease struck her most powerful tool. HER MAGICAL VOICE! The live performance marks the superstar entertainer’s first concert performance since revealing that she is living with stiff person syndrome, “a rare, progressive syndrome that affects the nervous system, specifically the brain and spinal cord,” according to the National Institute of Neurological Disorders and Stroke.