Objective: This is a case of steroid-responsive, autoimmune orofacial dyskinesia associated with extremely elevated striational [striated muscle] antibody. We present this instructive case to add to the expanding field of autoimmune movement disorders.

Background: A 71-year-old man with a past medical history of idiopathic monophasic transverse myelitis, hyperlipidemia, nephrolithiasis presented to our clinic for evaluation of 5 months of involuntary lingual movements. He endorsed a subacute onset of symptoms over 2 weeks with slurred speech, followed by involuntary movements of the tongue and infrequent jaw clenching. There were no preceding medication changes or illnesses. He reported a distant history of brief exposure to low dose compazine. On exam he exhibited persistent dyskinetic movements of the tongue. While undergoing workup, he was initiated on symptomatic therapy, deutetrabenazine, for a possible tardive phenomenon. This therapy partially suppressed his movements.

Method:
His extensive workup was notable for serum ANA positivity [1:320], low titer GAD 65 antibody [0.08] and extremely elevated striational antibody [1:61440]. Other indicative antibodies, including serum paraneoplastic panel, were negative. No metabolic abnormalities were discovered. EMG was normal. MRI brain was reassuring. MRI C-spine demonstrated decreased conspicuity of his established T2/STIR cord lesions from prior myelitis. PET brain and body were unrevealing.

Results: Given the subacute onset, nonspecific antibody positivity, prior transverse myelitis history, in addition to the lack of structural or metabolic etiologies, we suspected a primary autoimmune etiology and started him on an oral prednisone taper starting at 60 mg daily. On 1-month follow-up examination the tongue movements were no longer observed. Upon tapering his prednisone to 15mg daily, the movements reemerged. Given the steroid-responsiveness of his symptoms, he was commenced on mycophenolate.

Conclusion: This case illustrates an esoteric presentation of autoimmune orofacial dyskinesia. The exceedingly high striational antibody and unequivocal response to steroid therapy support an autoimmune etiology. Literature on movement disorders and striational antibody is limited. In this case, we contend that the striational antibody is likely a biomarker of autoimmunity rather than pathogenic.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-case-of-autoimmune-orofacial-dyskinesia-associated-with-striational-antibody/