A Case of Sensory Ataxia and Cardiac Hypertrophy Associated with Anti-Voltage Gated Potassium Channel (VGKC) Autoantibodies.

Objective: To describe laboratory findings in a teenager with progressive ataxia and hypertrophic cardiomyopathy (HCM). Background: There are reported cases of ataxia linked to VGKC autoantibodies, however they are typically related to cerebellar dysfunction. Cases of limbic encephalitis, Morvan’s syndrome and acquired neuromyotonia have been described in the setting of VGKC autoantibodies. Design/Methods: Here we describe a 19 year old male with history of scoliosis, concussion, and myopic astigmatism, who presented for an evaluation of abnormal gait, which progressively got worse over a course of 6 months. Neurologic exam revealed bilateral finger-to-nose dysmetria, decreased vibration sense over the lower extremities, Romberg (+) with an ataxic gait. Results: A brain and spine MRI was suggestive of non-specific white matter hyperintensities in the brain, without evidence of cerebellar dysfunction and syrinx over T5 through T9. Electromyography (EMG) testing revealed an acquired demyelinating generalized peripheral neuropathy, affecting sensory fibers, consistent with sensory ataxia. Echocardiogram was consistent with HCM. Whole exome sequencing was unrevealing. Laboratory work up including CBC, BMP, LFT, lipid panel, AFP, heavy metal, hepatitis panel, HIV, VLCFA, alpha galactosidase, anti-GALOP, anti-GM1, anti-asialo GM1, anti-GD1b, anti-GD1a, anti-sulfatide, anti-SGPG and anti-MAG were all found to be normal, except mildly low vitamin E levels, which were treated. Paraneoplastic panel identified VGKC antibodies at a level of 6250 pmol/L. PET/CT whole body scan was normal. Patient received monthly IVIG therapy. On a 6 month follow-up, VGKC antibodies decreased to 425pmol/L, EMG was unchanged, and gait significantly improved. Conclusions: There are no reported cases in the literature with co-existent findings of sensory ataxia, HCM, and positive VGKC autoantibodies to the best of our knowledge. The spinal syrinx in this patient was an incidental finding, unlikely to have contributed to his symptomatology. However, good response to IVIG therapy is more suggestive of an underlying autoimmune process. Disclosure: Dr. Alessi has nothing to disclose. Dr. Kaur has nothing to disclose. Dr. Manganas has nothing to disclose. Dr. Bindra has nothing to disclose.