Delusions of parasitosis involves the belief by the patient that he or she is infested with parasites. The belief may range from the plausible to the frankly psychotic. The more serious forms are difficult to treat.
Features of the delusion:
(1) a belief of having being infested by a parasite
(2) belief associated with distress for the patient
(3) belief persists despite an absence of objective findings and strong evidence to the contrary
(4) an underlying organic, psychiatric, or social disorder is usually present
Spectrum in the disorder: from normal to frank psychosis:
(1) concern about possible infestation, often after contact with a person with parasites, a dirty person, or travel to a foreign country
(2) anxiety or phobia about a possible infestation
(3) complaints of something crawling on or in the skin (tactile hallucinosis)
(4) excessive scratching or picking at the skin to remove the parasites
(5) delusional belief of infestation
The infesting agent may range from small insects (fleas, lice, etc.) to medical parasites (larva migrans, trematodes, etc.) to unspecified or fanciful bugs.
Demographics:
(1) The disorder peaks between age 40 and 60 years of age.
(2) There is a slight female predilection in patients <= 50 (1.4 to 1), but in patients > 50 this becomes more pronounced (5 to 1).
Associated findings:
(1) The belief may be an isolated finding or part of a complex problem.
(2) Patients often exhibit social isolation.
(3) Patients may engage in compulsive cleaning rituals.
(4) Some patients may lose their jobs.
(5) Some patients may resort to a frequent change in residence.
(6) Some patients dispose possessions and pets, sometimes putting the pets to death.
(7) Sometimes a secondary gain can be identified.
(8) Some patients show an above average intelligence.
(9) It may progress from an acute phase to a less bothersome chronic phase that can last for years.
(10) The patients often give a history of seeing many physicians who have all been unsuccessful in diagnosing and/or treating the problem.
(11) It may be a shared delusion with close family and friends ("folie a' trois", see chapter on psychiatry)
(12) There is often a poor response to interventions.
Treatment recommendations (see Wykoff, 1987):
(1) Be certain of the diagnosis. Look carefully for any underlying medical conditions.
(2) Listen carefully to the patient's history.
(3) Ask the patient how the condition has affected his or her life.
(4) Work to establish a common bond with the patient. Avoid confrontation.
(5) Be alert to any area in which the patient will allow help.
(6) Try to reduce the patient's sense of isolation.
(7) Consider the use of medicine to decrease the patient's anxiety and/or psychotic thinking.
Specialty: Infectious Diseases
ICD-10: ,
