Anti-Yo antibody associated axial movement disorders - a novel phenotype in ANNS

Movement disorders, as an anti-neuronal antibody mediated neurological syndrome(ANNS), is usually associated with anti-CV2/CRMP5,Hu/ANNA1 and Contactin-associated protein-like 2 (CASPR2) antibodies. Anti-Yo antibody associated movement disorders are extremely rare.

We analysed the data of 47 patients with anti -Yo antibodies who presented over a period of 5 years (2019-2024) in a tertiary care institute. Those with movement disorder phenotype, without ataxia, were included. Other etiologies were excluded with relevant work up.

We report two elderly males in their sixties who presented with a subacute onset isolated progressive axial movement disorders, with positive anti-Yo antibody. One patient with axial myoclonus and camptocormia who did not initially respond to intravenous methylprednisolone had remarkable improvement with intravenous immunoglobulin and rituximab, while in the other treatment response was suboptimal.

Movement disorders due to anti-neuronal antibodies should be suspected when they develop subacutely, in older patients (> 50 years), have a progressive course beyond 3 months, associated with pain and constitutional symptoms like weight loss, all of which were present in our cases. Such intracellular Yo antigen induced ANNS usually have guarded response to immunomodulatory therapy compared to those mediated by antibodies against surface antigens, though one patient of ours had a remarkable improvement.