BACKGROUND Delusional parasitosis is characterized by a false belief of being infested with parasites, insects, or worms. This illness is observed in patients with Parkinson’s disease and is usually related to dopaminergic treatment. To our knowledge, no cases of delusional parasitosis have been reported as a premotor symptom or non-motor symptom of Parkinson’s disease. CASE SUMMARY A 75-year-old woman presented with a complaint of itching that she ascribed to the presence of insects in her skin, and she had erythematous plaques on her trunk, arms, buttocks, and face. These symptoms started two months before the visit to the hospital. She took medication, including antipsychotics, with a diagnosis of delusional parasitosis, and the delusion improved after three months. A year later, antipsychotics were discontinued, and anxiety and depression were controlled with medication. However, she complained of bradykinesia, masked face, hand tremor, and mild rigidity, and we performed fluorinated N-3-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropane positron emission tomography (PET), which showed mildly decreased DAT binding in the right anterior putamen and caudate nucleus. Parkinson’s disease was diagnosed on the basis of PET and clinical symptoms. CONCLUSION In conclusion, delusional parasitosis can be considered a non-motor sign of Parkinson’s disease along with depression, anxiety, and constipation.

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