Stiff Person Syndrome is caused by an autoimmune reaction where antibodies disrupt nerve signals that control muscles, leading to stiffness and painful spasms. Symptoms usually start with stiffness in the trunk and gradually spread to the limbs, worsening over time and affecting movement and balance. Although there is no cure, treatments like muscle relaxants, anti-anxiety medications, immunotherapy (such as IVIG), and physical therapy can help manage symptoms and improve quality of life, so early medical evaluation is important if symptoms appear.