Anti-IgLON 5 Disease

This review aims to give an overview about the current knowledge of this novel neurological disorder associated to IgLON-5 antibodies and its treatment. Anti-IgLON5 disease was first formally described in 2014. This newly discovered disorder recaps a complex neurological disorder with sleep, movement, and neuroimmunological and neurodegenerative aspects. The clinical manifestation of the anti-IgLON5 disease is very heterogeneous mostly including a sleep disorder with non-rapid eye movement (REM) sleep parasomnia and REM behavior disorder besides obstructive sleep apnea syndrome and stridor. Other neurological features (bulbar symptoms, gait abnormalities, cognitive dysfunction) are common. Until today, the mean age of diagnosis was mostly above the age of 60 with a balanced distribution of sex. Neuropathological examination showed neuronal loss and gliosis associated with an atypical tauopathy mainly involving the tegmentum of brainstem and hypothalamus. Although the function of the antibodies stays unclear so far, the evidence for the pathogenetic role of the antibody becomes more evident. Among the association to HLA-DRB1*10:01 and HLA-DQB1*05:01 as a potential factor for susceptibility, immunopathological findings are promising. So far, the pathophysiology of anti-IgLON5 disease is not sufficiently enlightened and needs more interdisciplinary approach to a better understanding of this interesting disorder at the border of autoimmunity and neurodegeneration. Immunotherapy has been frequently used but its therapeutic effect is limited.