Delusions of parasitosis
Alerts and Notices
Synopsis
The typical patient is a socially isolated middle-aged to elderly female, although delusions of parasitosis can affect both sexes and all ages. Patients will often appear anxious and overwhelmed. Skin lesions, when present, are self-induced with the fingernails or other implements.
The clinician should be aware of the "matchbox sign" – patients will often bring lint, pieces of skin, and other debris to an office visit in plastic wrap or matchboxes, claiming that these items represent evidence of parasitic infection. Even though these collections contain no parasites, the patient believes that they represent organisms, pieces of organisms, ova, or larvae.
There are several variations of this disorder:
- Folie à deux ("a madness shared by two") – when a delusion of infestation has been transmitted to a significant other.
- Folie à famille ("family madness") – when a delusion of infestation has been transmitted within a family to more than 2 members.
- Firm belief that a spouse, child, or pet is infested.
Patients with this disorder may have an increased risk of various general medical conditions.
Codes
ICD10CM:F22 – Delusional disorders
SNOMEDCT:
89809008 – Delusion of parasitosis
Look For
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Diagnostic Pearls
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Differential Diagnosis & Pitfalls
- Scabies / scabies (pediatric) – look for burrows
- Dermatitis herpetiformis – look for clustered vesicles on an urticarial base
- Pediculosis
- Mite dermatitis
- Grover disease
- Neurotic excoriations – no underlying delusions expressed
- Systemic diseases that may cause pruritus (see pruritus without rash)
- Neurologic disease (multiple sclerosis, brain tumor, neurotoxins)
- Caterpillar and moth dermatitis
- Fiberglass dermatitis (see irritant contact dermatitis)
- Schizophrenia
- Psychotic depression
- Dementia
- Drug-induced delusions of parasitosis (see drug-induced psychosis)
Best Tests
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Management Pearls
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Therapy
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Drug Reaction Data
Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.Subscription Required
References
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Last Reviewed:05/05/2019
Last Updated:09/17/2020
Last Updated:09/17/2020