This mutation was described by Karen Hsiao et al in two patients from a Swedish-American family. The disease manifests itself as psychotic manic-depression disturbances (responding to antidepressant treatment, lithium and neuroleptics), cognitive alterations leading to dementia, ataxia and parkinsonian features. The neuropathological picture is similar to that of IK; numerous PrP plaques and NFT composed of PHF (paired helical filaments) are visible. PrPd in plaques coexists with Aβ peptide.