The overlap between these disorders can best be seen as a pathological continuum with dopamine cell loss and widespread LRP observed in both PDD and DLB, with additional β-amyloid deposition and mild cortical and hippocampal atrophy observed in pure DLB, and with greater hippocampal and cortical degeneration associated with additional tau deposition observed in mixed DLB with AD, while AD has the β-amyloid and tau deposition without the widespread LRP. The gene discussed is MAPT; the disease is hippocampal atrophy.