Our patient was treated with corticosteroids and with plasma exchange: after the latter treatment, her cognitive deficits improved dramatically and her anti-IgLON5 serum titer decreased from 1:10,000 to 1:320: this suggests that in our patient cognitive decline could be related to the titer of anti-IgLON5 antibodies and that the antibodies play a role in the pathogenesis. Here, IGLON5 is linked to Mental deterioration.