In 2022, a 48-year-old male presented 8-year history of progressive abnormal movements, including chorea, dystonia, and tics, accompanied by irritability, sleep disturbance, and cognitive complaints. He was diagnosed with Huntington’s disease, started on tetrabenazeine and referred for subspecialty evaluation. Genetic testing was negative (16 CAG repeats). He was treated with high dose steroids with minor improvement, leading to further investigations. CSF showed no pleocytosis, mildly elevated protein and normal CSF cytology. A Mayo antibody panel was positive for anti-CASPR2 antibody. He was treated using steroids and PLEX resulting in 80% improvement in chorea. He was able to discontinue tetrabenazine. Maintenance immunotherapy was started with rituximab, and mycophenolate was added as he did not feel rituximab was adequate. On the combination, he has had near-complete resolution of his abnormal movements.