(057) A Picture Worth a Thousand Worms: A Case of Folie à Deux of Parasitosis in an Early-Onset Parkinson's Patient and Significant Other

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Background: Primary delusional parasitosis (delusional infestation or DI) is a somatic subtype of delusional ‎disorder, with delusion of infestation being the sole psychotic symptom. Secondary DI stems from another psychiatric ‎disorder or medical illness, and although rare, is associated with anti-Parkinson medications, antidepressants, and ‎antiepileptics, among others (Kemperman et al., 2022). Folie à deux (FAD) is a rare psychotic disorder in which two ‎intimately associated individuals simultaneously share similar or identical delusions. We present a rare case of FAD with ‎secondary DI in the context of early-onset Parkinson's and OCD.‎

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Case: D.A. was a 49-year-old woman with OCD, early-onset Parkinson's, hypothyroidism, Ehlers-Danlos, ‎Raynaud's, adrenal adenoma, and, recently, COVID-19, admitted to medicine for work-up of DI. She endorsed tactile ‎and visual hallucinations of worms, insects, larvae and biofilm, insomnia and fatigue. She exhibited "matchbox sign", ‎i.e., containers of urine and stool for testing and over 40 photographs of her tongue, extremities, saliva and urine, ‎allegedly capturing the parasites. Patient's partner endorsed seeing these living specimens and believed that D.A. was ‎experiencing true parasitosis. The disease was debilitating, causing D.A. to reside at a hotel to prevent transmission to ‎her child. Patient was prescribed fluvoxamine, atomoxetine, rasagiline, pramipexole, carbidopa-levodopa and ‎marijuana. Zonisamide was a newly added anti-Parkinson adjunct prior to her admission.‎

Medical workup was unremarkable. D.A. maintained frustration regarding dismissal of parasitosis. She had poor insight ‎and was nonadherent with quetiapine prescribed for insomnia and psychotic symptoms. She requested an infectious ‎disease consultation. D.A. was discharged with instructions to follow up at an integrated care program.‎

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Discussion: The two had a "codependent" relationship, which may precipitate the development of FAD, as ‎these patients are typically close relatives (Reich et al., 2019). D.A. was taking several DI-associated medications. We ‎recommended discontinuing zonisamide, as well as atomoxetine, which has documented association with DI (Howes, ‎et al., 2018). We posit that this is the first reported case of folie à deux with secondary delusional parasitosis, and ‎thereby enriches studies on both phenomena.‎

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Conclusion: We discuss the literature on FAD and medication-induced DI. We discuss identification and ‎management of FAD with secondary DI, emphasizing risk factor recognition and referral to integrative care, as patients ‎with DI are unlikely to accept antipsychotics or psychiatry referrals due to their steadfast delusions (Kemperman et al., ‎‎2022). We postulate that D.A.'s obsessions of betrayal by a significant other and "codependence" with her partner ‎increased their vulnerability to developing FAD. The treatment for FAD is to separate the patients and/or initiation of ‎an antipsychotic; we discuss barriers to management and the importance of collaborative care.‎

‎References‎
‎1. Kemperman PMJH, Bruijn TVM, Vulink NCC, Mulder MMC. Drug-induced Delusional Infestation. Acta Derm ‎Venereol. 2022 Mar 8;102:adv00663. doi: 10.2340/actadv.v102.183. PMID: 35170743; PMCID: PMC9558340.‎
‎2. Howes CF, Sharp C. Delusional infestation in the treatment of ADHD with atomoxetine. BMJ Case Rep. 2018 Sep ‎‎23;2018:bcr2018226020. doi: 10.1136/bcr-2018-226020. PMID: 30249731; PMCID: PMC6157501.‎
‎3. Reich A, Kwiatkowska D, Pacan P. Delusions of Parasitosis: An Update. Dermatol Ther (Heidelb). 2019 Dec;9(4):631-‎‎638. doi: 10.1007/s13555-019-00324-3. Epub 2019 Sep 13. PMID: 31520344; PMCID: PMC6828902.‎