This study will explore the role of various immune factors involved in producing the disease symptoms in stiff-person syndrome (SPS) and follow disease progression in patients. SPS is a progressive disease in which unexpected noises, touches or stressful events set off muscle spasms and stiffness. It is thought to be an autoimmune disease in which the body produces antibodies that attack certain healthy tissues. A better understanding of the disease may help researchers design new therapies.