Despite a lack of definitive autopsy data, the clinical features in the present case were as follows: (1) person DMS as an initial symptom appeared during the progressive course of a patient with a V180I mutation in PRNP; (2) the slow progression was similar to the clinical presentation of DLB; and (3) the genetic mutation V180I provided a conclusive diagnosis of genetic CJD. The gene discussed is PRNP; the disease is Lewy body dementia.