Delusional Infestation and Chronic Pruritus: A Review

Abstract

The literature on chronic pruritus, paresthesia and delusional infestation indicates that a wide variety of conditions ranging from AIDS to vitamin deficiencies may cause these symptoms. In many, or perhaps most of these cases, activation of itch pathways seems to be the underlying cause of the skin sensations and perhaps even the visual hallucinations characteristic of delusional infestation. The principle difference between diagnoses of chronic pruritus and delusional infestation appears to lie in the patient's interpretation of the cause of the symptoms, rather than underlying physiological differences. Delusional infestation, paresthesia and chronic pruritus must be considered symptoms of underlying conditions.

Delusional infestation: a prototype of psychodermatological disease

“…However, these extrapolations are likely inaccurate. For example, a review article produced by the Department of Entomology and Nematology from the University of California, Davis, explained the Centers for Disease Control's calculation of 3.7 Kaiser Permanente Healthcare DI patients per 100,000 patients in central California . A paper that surfaced in 2015 referenced an incidence of 1.9 DI patients per 100,000 patients in Minnesota.…”

“…Delusional infestation is a psychiatric condition classified in the Diagnostic and Statistical Manual of Mental Disorders (DSM‐5) as a delusional disorder, somatic type . The delusion in these patients is that they mistakenly believe their skin or other body parts are infested by small, living organisms . Some common organisms in these delusions include worms, flies, lice, and mites.…”

“…Secondary delusional infestation also presents as a monosymptomatic, unwavering delusion with abnormal, cutaneous sensations, but it occurs secondary to a medical condition, medication, or another psychiatric disorder, most commonly substance abuse . Refer to Table for a comprehensive list of medical conditions, medications, and illicit drugs which have contributed to case reports of secondary DI in the past.…”

British Association of Dermatologists’ guidelines for the investigation and management of generalized pruritus in adults without an underlying dermatosis, 2018

“…Chronic generalized pruritus is found commonly in several psychiatric disorders including depression, anxiety disorder, obsessive compulsive disorder, substance abuse and delusional infestation . However, one should always look for a physical cause before labelling such patients as ‘psychogenic’.…”

Formication, tactile hallucinations, delusional parasitosis, and Morgellons: Enough to make your skin crawl

“…It is often associated with low income, divorce, and emotional stress. Individuals with delusional parasitosis typically have average or above average intelligence, have generally intact reality testing, and may lack a fear of insects …”