Delusions of parasitosis: a review.

Patients who are erroneously convinced that they harbor dermatologic parasites present a diagnostic and therapeutic challenge to the practitioner. Delusions of parasitosis can exist as an isolated psychosis or as part of a much more complicated medical and/or psychiatric illness. To diagnose these patients, physicians must be familiar with the patterns of presentation usually seen in patients with delusions of parasitosis and must be confident that other psychiatric and/or medical conditions that could be causing the symptoms--including true parasitosis--have been ruled out. Clinical signs, such as the presence of cutaneous lesions on exposed and accessible parts of the body (wounds self-inflicted in efforts to extricate parasites with needles, knives, or fingernails), and behavioral signs, such as the collection of bottles and jars purported to contain samples of the parasites, are characteristic. These patients can be rigid, antagonistic, distant, and demanding; they may write long letters to physicians describing their parasites in detail, enclosing drawings or samples. Psychotherapy, with or without confrontational denial, has a reported efficacy of approximately 10%; placebo therapy is usually not recommended. The recent application of a new neuroleptic agent, pimozide, to the treatment of this disorder is controversial and a new neuroleptic agent, pimozide, to the treatment of this disorder is controversial and needs further study. Guidelines for an appropriate approach to patients with delusions of parasitosis include the necessity of identifying medical or psychiatric disease, if present, and of listening carefully to the patient's history.(ABSTRACT TRUNCATED AT 250 WORDS)