Capgras delusion for animals and inanimate objects in Parkinson's Disease: a case report

Capgras delusion is a delusional misidentification syndrome, in which the patient is convinced that someone that is well known to them, usually a close relative, has been replaced by an impostor or double. Although it has been frequently described in psychotic syndromes, including paranoid schizophrenia, over a third of the documented cases of Capgras delusion are observed in patients with organic brain lesions or neurodegenerative disease, including Parkinson's Disease. Variants of Capgras involving animals or inanimate objects have also been described. The etiology of Capgras in Parkinson's remains unclear, but may arise from a combination of factors, such as frontal lobe dysfunction and dopaminergic medication.

We present the case of a 53-year old right-handed female with Parkinson's disease who developed Capgras delusion during treatment with dopamine agonists and Levodopa/Carbidopa. She became convinced that her pet dogs and the plants in her garden had been substituted by identically looking ones. Our patient was initially treated with Quetiapine, with no improvement, and subsequently treated with Clozapine, which lead to partial regression of her symptoms. Neuropsychological Evaluation showed Mild Cognitive Impairment in Executive Functions.

Given the clinical history, onset and evolution of symptoms we believe our patient's delusion resulted from the overlap of dopaminergic medication and Mild Cognitive Impairment in executive functions. Zoocentric Capgras, the variant we describe, has been rarely described in scientific literature, and we believe it is of interest due to its unusual characteristics.