Stiff Person Syndrome (SPS) is an uncommon disease. Due to the ability to mimic degenerative, immune-mediated, or neoplastic diseases with motor manifestations, it should remain on the differential in many diseases.

A previously healthy 44-year-old right handed woman presented with progressive dysarthria and left sided stiffness. She had a history of low back pain. She noticed smaller handwriting, motion sickness, double vision when looked to the left and moving globally slower. Denied cognitive or mood changes.  On examination she had normal higher cortical function, had a slow rate of speech with impaired lingual and guttural phonemes. Extraocular movements showed full pursuits and saccades. Optokinetic response and ocular pursuits were slowed in vertical and horizontal directions. Her left arm and left leg were rigid. Finger and toe tapping were slow on the left. Motor strength was full. There was no tremor or ataxia. She was hyperreflexic throughout. Gait was slow and stride length was reduced on the left leg. Her left arm did not swing and adopted a dystonic elbow flexion posture. Pull test was normal (Video). Levodopa trial showed no benefit. Serologic testing resulted positive for GAD65.