Iglon5-antibody disease: a case series

IgLON5-antibody disease is a rare disorder first described in 2014 with features which interfaces both autoimmune and neurodegenerative pathophysiological processes. It has a strong HLA association, and the diagnosis is confirmed by the presence of antibodies which bind the extracellular domain of a neuronal cell adhesion protein, Iglon5. Post-mortem findings reveal this correlates with a tauopathy and subsequent neurodegeneration affecting the hypothalamus and tegmental brainstem. We present three cases and describe their history, disease progression, management and treatment responses. We found a remarkably consistent clinical phenotype which was characterised by REM and NREM parasomnias, bulbar dysfunction causing distinctive inspiratory noises, and mixed movement disorders. Our cases were diagnosed between 1.5-2 years from symptom onset. One patient died following treatment with IVIg, whilst two have been diagnosed within the last month and started on plasma exchange and immunotherapy. We will report their clinical follow up. IgLON5-antibody disease is often diagnosed late, it is thought after irreversible neurodegeneration has occurred and symptoms are advanced. We hope to raise awareness of the classical myriad of presenting symptoms and lead to earlier diagnosis, within which a window of opportunity may exist to instigate immunotherapy and arrest ongoing autoimmune processes.