Delusional parasitosis

Delusional parasitosis
Classification and external resources
ICD-10 F22
DiseasesDB 9622
eMedicine derm/939

Delusional parasitosis, also known as delusional infestation[1] or Ekbom's syndrome,[2][3] is a delusional disorder in which individuals incorrectly believe they are infested with parasites, insects, or bugs, whereas in reality no such infestation is present.[4] Individuals with delusional parasitosis usually report tactile hallucinations known as formication, a sensation resembling insects crawling on or under the skin.

Delusional parasitosis is a mental disorder characterized by a fixed, false belief that a skin infestation exists, which is in contrast to cases of actual parasitosis, such as scabies and infestation with Demodex, in which a skin infestation is present and identifiable by a physician through physical examination or laboratory tests.[5][6]

Morgellons is poorly understood but appears to be a form of this condition. The alternative name, Ekbom's syndrome, was named after Swedish neurologist Karl-Axel Ekbom,[7] who published seminal accounts of the disease in 1937 and 1938. It is differentiated from Willis-Ekbom Disease (WED), another name for restless legs syndrome.

Signs and symptoms

Details of delusional parasitosis vary among sufferers, it manifests as a crawling and pin-pricking sensation, but it 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; often associated with menopause, or sometimes exposure to household cleaning products).[4][8] Sufferers may injure themselves in attempts to be rid of the "parasites". Some are able to induce the condition in others through suggestion, in which case the term folie à deux may be applicable.[3][9]

Nearly any marking upon the skin, or small object or particle found on the person or his 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.[4] This presentation of "evidence" is known as "the matchbox sign" because the "evidence" is frequently presented in a small container, such as a matchbox.[3]

A study conducted of 108 patients at the Mayo Clinic was published in Archives of Dermatology on May 16, 2011. The study failed to find evidence of skin infestation despite doing skin biopsies and examining specimens provided by the patients. The study, which was conducted between 2001 and 2007, concluded that the feeling of skin infestation was delusional parasitosis.[10][11]

Delusional parasitosis is seen more commonly in women, and the frequency is much higher past the age of 40.[3][12]

Delusory cleptoparasitosis is a form of delusion of parasitosis where the person believes the infestation is in their dwelling, rather than on or in their body.[13]

Morgellons is poorly understood but appears to be a form of delusional parasitosis in which people have painful skin conditions that they believe contain fibers of various kinds.[14][15][16][17][18]


Delusional parasitosis is divided into primary, secondary functional, and secondary organic groups.[19]


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",[20] and sometimes as "true" delusional parasitosis. In the 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 or substance (medical or recreational) use. In the DSM-IV this corresponds with "psychotic disorder due to general medical condition". Physical illnesses that can underlie secondary organic delusional parasitosis include: hypothyroidism, cancer, cerebrovascular disease, tuberculosis, neurological disorders, vitamin B12 deficiency, and diabetes mellitus. Any illness or medication for which formication is a symptom or side effect can become a trigger or underlying cause of delusional parasitosis.

Other physiological factors which can cause formication and thus can sometimes lead to this condition include: menopause (i.e. hormone withdrawal); allergies, and drug abuse, including but not limited to cocaine and methamphetamine (as in amphetamine psychosis).[12] It appears that many of these physiological factors, as well as environmental factors such as airborne irritants, are capable of inducing a "crawling" sensation in otherwise healthy individuals; however, some people become fixated on the sensation and its possible meaning, and this fixation may then develop into delusional parasitosis.[12]


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.[4]

Society and culture


Main article: Morgellons

The name was coined in 2002 by the founder of the Morgellons Research Foundation, Mary Leitao,[21] who revived it from a letter written by a physician in the mid-1600s.[22] Leitao and others involved in her foundation who self-identified as having Morgellons successfully lobbied members of the U.S. Congress and the U.S. Centers for Disease Control and Prevention (CDC) to investigate the condition in 2006.[23][24] CDC researchers issued the results of their multi-year study in January 2012, indicating that there were no disease organisms present in people with Morgellons and that the fibers found were likely cotton, and concluded that the condition was "similar to more commonly recognized conditions such as delusional infestation".[25][26]

See also


  1. Freudenmann, R. W.; Lepping, P. (2009). "Delusional Infestation". Clinical Microbiology Reviews. 22 (4): 690–732. doi:10.1128/CMR.00018-09. PMC 2772366Freely accessible. PMID 19822895.
  2. Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN 1-4160-2999-0.
  3. 1 2 3 4 Hinkle, N.C. (2011). "Ekbom Syndrome: a delusional condition of "bugs in the skin"". Curr Psychiatry Rep. 13 (3): 178–86. doi:10.1007/s11920-011-0188-0. PMID 21344286.
  4. 1 2 3 4 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.
  5. Kligman, Albert M (2011). "Demodex folliculorum: Requirements for Understanding Its Role in Human Skin Disease". Journal of Investigative Dermatology. 131 (1): 8–10. doi:10.1038/jid.2010.335. PMID 21157421.
  6. Jing, X., Shuling, G. and Ying, L. (2005). "Environmental scanning electron microscopy observation of the ultrastructure of Demodex.". Microsc. Res. Tech. 68: 284–289. doi:10.1002/jemt.20253.
  7. Ekbom's syndrome II at Who Named It?
  8. Amin, Omar (February 15, 2015). "The delusion of "delusional parasitosis"" (PDF). Parasite Testing.
  9. 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.
  10. Hylwa SA, Bury JE, Davis MD, Pittelkow M, Bostwick JM (2011). "Delusional infestation, including delusions of parasitosis: results of histologic examination of skin biopsy and patient-provided skin specimens". Arch Dermatol. 147 (9): 1041–5. doi:10.1001/archdermatol.2011.114. PMID 21576554.
  11. Walsh, Nancy; Zalman S. Agus (May 16, 2011). "Bugs and Worms in Patients' Heads, Not the Skin". MedPage Today. Retrieved 16 May 2011.
  12. 1 2 3 Hinkle, Nancy C (2000). "Delusory Parasitosis" (PDF). American Entomologist. 46 (1): 17–25.
  13. Grace, Kenneth J (1987). "Delusory Cleptoparasitosis: Delusions of Arthropod Infestation in the Home". Pan-Pacific Entomologist. 63 (1): 1–4.
  14. Halvorson, CR (October 2012). "An approach to the evaluation of delusional infestation.". Cutis. 90 (4): E1–4. PMID 24005827.
  15. Shmidt, E; Levitt, J (February 2012). "Dermatologic infestations.". International journal of dermatology. 51 (2): 131–41. PMID 22250620.
  16. Harth, W; Hermes, B; Freudenmann, RW (April 2010). "Morgellons in dermatology.". Journal der Deutschen Dermatologischen Gesellschaft = Journal of the German Society of Dermatology : JDDG. 8 (4): 234–42. PMID 19878403.
  17. Freudenmann, RW; Lepping, P (October 2009). "Delusional infestation.". Clinical microbiology reviews. 22 (4): 690–732. PMC 2772366Freely accessible. PMID 19822895.
  18. Simpson, L; Baier, M (August 2009). "Disorder or delusion? Living with Morgellons disease.". Journal of psychosocial nursing and mental health services. 47 (8): 36–41. PMID 19681520.
  19. Freinhar, Jack P (1984). "Delusions of parasitosis". Psychosomatics. 25 (1): 47–53. doi:10.1016/S0033-3182(84)73096-9.
  20. FreedBerg; et al. (2003). Fitzpatrick's Dermatology in General Medicine (6th ed.). McGraw-Hill. p. 389. ISBN 0-07-138076-0.
  21. Harlan, Chico (2006-07-23). "Mom fights for answers on what's wrong with her son". Pittsburgh Post-Gazette. Retrieved 2007-08-04.
  22. Edwards, Stassa (April 15, 2015), "Real Delusions of an Unreal Disease: A History of Morgellons", Jezebel
  23. Schulte, Brigid (January 20, 2008). "Figments of the Imagination?". Washington Post Magazine. p. W10. Retrieved 2008-06-09.
  24. "Unexplained Dermopathy (aka "Morgellons"), CDC Investigation". Centers For Disease Control. November 1, 2007. Retrieved 2011-05-09.
  25. Pearson, Michele L.; Selby, Joseph V.; Katz, Kenneth A.; Cantrell, Virginia; Braden, Christopher R.; Parise, Monica E.; Paddock, Christopher D.; Lewin-Smith, Michael R.; Kalasinsky, Victor F.; Goldstein, Felicia C.; Hightower, Allen W.; Papier, Arthur; Lewis, Brian; Motipara, Sarita; Eberhard, Mark L.; Unexplained Dermopathy Study, Team (2012). "Clinical, Epidemiologic, Histopathologic and Molecular Features of an Unexplained Dermopathy". PLoS ONE. 7 (1): e29908. Bibcode:2012PLoSO...729908P. doi:10.1371/journal.pone.0029908. PMC 3266263Freely accessible. PMID 22295070.
  26. Aleccia, JoNel. "Mystery skin disease Morgellons has no clear cause, CDC study says". NBC News. Retrieved 2 April 2015.

Further reading

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