A rare delusional disorder of mistaken identity, in which a person is convinced that different people are actually the same person, changing their appearance or disguising themselves. Often accompanied by paranoid ideas, such as that a masked person is harassing or harming. The condition is usually associated with psychiatric illnesses such as schizophrenia, schizoaffective disorder, or mood disorders with psychotic symptoms, and can also occur after brain injuries, especially those involving the right hemisphere or frontal lobes. Treatment includes antipsychotic medications and psychotherapy.