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Delusional parasitosis
ICD-9 300.29
OMIM [1]
DiseasesDB 9622
MedlinePlus [2]
eMedicine derm/939
MeSH {{{MeshNumber}}}

Delusional parasitosis is a form of psychosis in which sufferers hold a delusional belief they are infested with parasites.[1]

Delusional parasitosis is also referred to as Ekbom's syndrome, named after a Swedish neurologist, Karl Axel Ekbom,[2] who published seminal accounts of the disease in 1937 and 1938. It is not to be confused with Wittmaack-Ekbom syndrome (restless legs syndrome).


Delusional parasitosis is divided into primary, secondary functional and secondary organic groups.[3]


In primary delusional parasitosis, the delusions comprise the entire disease entity, there is no additional deterioration of basic mental functioning or idiosyncratic thought processes. The parasitic delusions consist of a single delusional belief regarding some aspect of health. This is also referred to as monosymptomatic hypochondriacal psychosis, and sometimes as "true" delusional parasitosis. In DSM-IV, this corresponds with "delusional disorder, somatic type".

Secondary functional

Secondary functional delusional parasitosis occurs when the delusions are associated with a psychiatric condition such as schizophrenia or clinical depression.

Secondary organic

Secondary organic delusional parasitosis occurs when the state of the patient is caused by a medical illness, medication or substance abuse. In DSM-IV this corresponds with "psychotic disorder due to general medical condition." Physical illnesses that can underly Secondary organic delusional parasitosis include: hypothyroidism, cancer, cerebrovascular disease, tuberculosis, neurological disorders, vitamin B12 deficiency, and diabetes mellitus. Any illness of medication of which formication is a symptom or side effect can become a trigger or underlying cause of delusional parasitosis.

Other physiological factors which can contribute to the condition include menopause; allergies; drug abuse, including but not limited to cocaine and methamphetamine (as in amphetamine psychosis); certain medical conditions; and poor nutrition.[4] It appears that many of these physiological factors, as well as environmental factors such as airborne irritants, are capable of inducing the "crawling" sensation in otherwise healthy individuals, but that some people become fixated on the sensation, and this fixation may then develop into delusional parasitosis.[4]


Details of delusional parasitosis vary among sufferers, but is most commonly described as involving perceived parasites crawling upon or burrowing into the skin, sometimes accompanied by an actual physical sensation (known as formication).[1] Individuals suffering from this condition may injure themselves in attempts to be rid of the "parasites", and sometimes are able to induce the condition in others through suggestion (a phenomenon dubbed folie à deux).[5] Nearly any marking upon the skin, or small object or particle found on the person or their clothing, can be interpreted as evidence for the parasitic infestation, and sufferers commonly compulsively gather such "evidence" and then present it to medical professionals when seeking help.[1] The condition is seen most commonly in women, and the frequency is much higher past the age of 40.[4]


Treatment of secondary forms of delusional parasitosis are addressed by treating the primary associated psychological or physical condition. The primary form is treated much as other delusional disorders and schizophrenia. In the past, pimozide was the drug of choice when selecting from the typical antipsychotics. Currently, atypical antipsychotics such as olanzapine or risperidone are used as first line treatment. However, it is also characteristic that sufferers will reject the diagnosis of delusional parasitosis by medical professionals, and very few are willing to be treated, despite demonstrable efficacy of treatment.[1]


The term "Morgellons" was introduced in 2002 to describe a skin condition characterized by lesions and fibers on and under the skin and certain systemic symptoms. A majority of health professionals, including most dermatologists, regard Morgellons as a manifestation of other known medical conditions, including delusional parasitosis[6][7][8] and believe any fibers found are from textiles such as clothing.[9] The Morgellons Research Foundation, a non-profit advocacy organization, believes that it is a new infectious disease that will be confirmed by future research.[10][11] "Other health professionals don't acknowledge Morgellons disease or are reserving judgment until more is known about the condition."[12] Research into the condition is ongoing.

See also


  1. 1.0 1.1 1.2 1.3 Webb, J. P., Jr. (1993). Case histories of individuals with delusions of parasitosis in southern California and a proposed protocol for initiating effective medical assistance. Bulletin of the Society of Vector Ecologists 18 (1): 16-24.
  2. Who Named It synd/2338
  3. Freinhar, Jack P. (1984). Delusions of parasitosis. Psychosomatics 25 (1): 47-53.
  4. 4.0 4.1 4.2 Hinkle, Nancy C. (2000). Delusory Parasitosis. American Entomologist 46(1): 17-25.
  5. Koblenzer, C. S.. (1993). The clinical presentation, diagnosis and treatment of delusions of parasitosis--a dermatologic perspective. Bulletin of the Society of Vector Ecologists 18 (1): 6-10.
  6. Mysterious 'Morgellons disease' prompts US investigation, Emma Marris, Nature Medicine, 30 August 2006
  7. Delusions of Parasitosis Noah Scheinfeld, May 4, 2007
  8. Dunn, Jeffrey, Michael B. Murphy and Katherine M. Fox (August, 2007). Diffuse Pruritic Lesions in a 37-Year-Old Man After Sleeping in an Abandoned Building. The American Journal of Psychiatry 164: 1166-1172.
  9. includeonly>Elaine Monaghan. "All in the head?", The Times, May 19, 2006. Retrieved on 2007-08-14.
  11. Savely VR, Leitao MM, and Stricker, RB. The mystery of Morgellons disease: infection or delusion? Am J Clin Dermatol. 2006;7(1):1–5 PMID 16489838
  12. Morgellons disease: Managing a mysterious skin condition. Mayo Clinic. URL accessed on 2007-08-04.
  • Enoch, D. & Ball, H. (2001) Ekbom's Syndrome (Delusional parasitosis). In Enoch, D. & Ball, H. Uncommon psychiatric syndromes (Fourth edition) pp209-223. London: Arnold. ISBN 0340763884

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