Successful Treatment of Delusional Infestation with Dupilumab: Case Report

Abstract

Delusional infestation (DI) is a psychodermatologic disorder marked by fixed, false belief of parasitic infestation, often accompanied by significant distress. The pathogenesis remains incompletely understood. Currently, the standard of care is antipsychotic medication. We report the case of a 71-year-old man with Parkinson’s disease and a four-year history of treatment-resistant DI, who experienced complete symptom resolution following the initiation of dupilumab. The patient presented with sensations of worms, bugs, and fibers invading his body, severely impacting his quality of life. Skin findings were absent, and blood work revealed persistent peripheral eosinophilia. Multiple treatments had been trialed, including antiparasitics, antihistamines, topical steroids, antifungals, and immunosuppressants, which were unsuccessful or discontinued due to side effects. Following the initiation of dupilumab, the patient reported near-complete relief from DI symptoms. This case demonstrates dupilumab’s potential to act as a novel treatment for DI. Dupixent blocks interleukins 4 and 13, key contributors for Th2 inflammatory pathways, which may indirectly reduce delusional ideation by resolving symptoms of formication and itch. To our knowledge, this is among the first reported cases to describe complete symptom resolution of DI with dupilumab. These findings suggest that immunomodulatory therapy may be an effective treatment in managing select cases of DI, especially in the presence of peripheral eosinophilia. Further research is warranted to explore the neuroimmunologic underpinnings of DI and expand therapeutic options for this challenging condition.