Two Cases of Delusion of Inanimate Doubles, a Variant of Capgras Syndrome

Objective: The delusion of inanimate doubles (DID) is a misidentification syndrome characterized by a belief in inanimate doubles. A variant of Capgras syndrome (CS), research suggests that it occurs in 10% of cases. Typically, CS involves the delusion that a familiar person has been replaced by an imposter. Reduplicative paramnesias (RP) are delusions about a place being doubled. CS and RP are found after a variety of neurologic insults, most commonly neurodegenerative disease, and are hypothesized to involve right frontal lesions. We describe two cases (B and K) of DID also suspicious for frontal lobe pathology. Method: Both women were in their 70s and had a long (~5 years), insidious history of decline with recent worsening. Both experienced sleeplessness and had normal blood work, with the exception of high cholesterol levels for K. MRI was unavailable. Both showed delusions of duplicated objects in the home (S, water heater; B, dishes and furniture replaced with a nearly identical one by acquaintances), whereas K also evidenced CS for her daughters, RP for cities, visual hallucinations, misperceptions, falls, and periods of confusion. Results: On exam, both women evidenced executive dysfunction, with anxiety about the delusions. K also had memory, visuospatial, and mild language impairments. K was diagnosed with Lewy Body Dementia and B with non-amnestic Mild Cognitive Impairment. Conclusion: Absent of their delusions, both women would have been able to remain living independently. These cases of DID support a relationship with frontal pathology. If diagnosed sooner, appropriate treatment may have allowed them to remain independent for longer.