Stiff Person Syndrome (SPS) is a rare neurological disorder of unclear cause characterized by progressive muscular rigidity and stiffness. The stiffness primarily affects the truncal muscles and is superimposed by spasms, resulting in postural deformities. Early symptoms include limb stiffness, stiff muscles in the trunk, posture problems from a rigid back muscles (this can cause you to hunch over), painful muscle spasms, walking difficulties, and sensory issues.
SPS is a rare autoimmune neurological disorder with no cure at the time of this writing. It causes severe muscle spasms, most notably with muscles locking up and becoming "stiff as a board" no matter how the patient tries to move them. Spasms can generate enough force to fracture bone.
Here's an example: A person with SPS may have difficulty walking due to stiffness in their legs. They may also have difficulty standing up straight due to stiffness in their back muscles. In addition, they may experience painful muscle spasms that can be triggered by noise, touch, or emotional distress.
