Le délire d’infestation cutanée parasitaire, ou syndrome d’Ekbom, est une pathologie rare caractérisée par la conviction inébranlable que de petits animaux (insectes, asticots, vermines) grouillent sous la peau. Plus souvent observé par les dermatologues que par les psychiatres, il affecte le plus souvent des personnes âgées (deux ou trois femmes pour un homme) vivant seules dans des conditions matérielles précaires. Typiquement amélioré sinon guéri par le pimozide, il relève le plus souvent désormais d’un traitement par antipsychotiques atypiques. Les formes secondaires sont plus fréquentes que les formes primaires. Depuis quelques années se répand au États-Unis la « maladie des Morgellons » qui affecterait plusieurs dizaines de milliers de personnes (avec une fondation privée pour la recherche), et qui ne serait pour les professionnels et le CDC qu’un délire parasitaire propagé à une vaste population par le biais d’Internet (Web), véritable délire collectif.

Ekbom’s syndrome (delusional cutaneous parasitosis) is an “uncommon psychiatric syndrome” characterized by a strong certainty that insects, lice, maggots or other small vermin are living or otherwise thriving in the skin and sometimes in other parts of the body (Enoch, Ball, 2001). Described by Thiebierge (1894) and Perrin (1896), two dermatologists, it received the name of zoophobia, parasitophobia, acariophobia. The eponymous designation is Ekbom syndrome from the Swedish neurologist who described its principal manifestations (1937-1938). Annika Skott (1978) published the pivotal monograph (based on 354 cases, 1954-1961) with the title term Dermatozoenwahn coined by Ekbom, as did Michael Musalek in his book published in German (1991). It is a rare condition (7 per 10 000 psychiatric admissions according to Marneros et al (1998). Several other surveys report series of patients seen in dermatology clinics. It is seen occasionally by dermatologists, exceptionally by psychiatrists. Typically it is supposed to be cured by Pimozide or other neuroleptic or new antipsychotic drugs. A majority of patients are aged females, living alone in bad material conditions. Some patients are chronically addicted to cocaine and amphetamine-like drugs. This delusion could be psychologically contagious with cases of “délire à deux (à trois)”, or by proxy… Another phenomenon is called “the Morgellons disease”, described by Thomas Browne (1690) (A Letter to a friend) in Languedoc. For the CDC there is no proof that the Morgellons is a separate pathology. On the contrary, Mary Leitao (McMurray, Pennsylvania 2002) gave the name of “Morgellons disease” to what she considered the resurgence of an ancient and forgotten malady, which affected children of Languedoc in 17th century. There is an Morgellons Research Foundation (MRF) to encourage research about this infectious malady similar to scabies and pediculosis. The website claims that more than 12 000 families affected by Morgellons are registered with the foundation, and self accounts of affected individual are over flowing.