Seven patients presenting diverse neural autoantibodies in serum (n = 2 neuropil antibodies, n = 2 IgLON5 antibodies, n = 1 GFAP antibodies, n = 1 flotilin 1/2 antibodies, and n = 1 neurexin 3alpha antibodies) were identified who exhibited a cognitive impairment (n = 3 with dementia, n = 4 with MCI). Here, IGLON5 is linked to dementia.