Delusional parasitosis

Delusional parasitosis or Ekbom's Syndrome is a rare disorder in which sufferers hold a delusional belief they are infested with parasites. A related symptom involving a tactile hallucination of insects, snakes, or other vermin crawling over the skin is known as formication. The origin of this word is from the Latin formica, "ant".

It is not to be confused with Wittmaack-Ekbom or restless legs syndrome. Unfortunately, this is also referred to in short as "Ekbom's Syndrome" leaving the audience having to infer the particular meaning from the context. It is named after a Swedish neurologist, Karl Axel Ekbom, who published seminal accounts of the disease in 1937 and 1938.

Presentation
The sufferer typically reports parasites to exist under the skin, around or inside body openings, in the stomach or bowels and may include a belief that the parasites infest the sufferer's home, surroundings or clothing.

A person holding such a belief may approach doctors or dermatologists asking for treatment for the supposed infestation, and will often bring small particles, dust, skin flakes and other material for the doctor to inspect. Since the material may be carried in an envelope or matchbox, this presentation is known as the "matchbox sign."

Stimulant drug abuse (particularly amphetamine and cocaine) can lead to delusional parasitosis. For example, excessive cocaine use can lead to an effect nicknamed "cocaine bugs" where the affected person believes he has, or feels parasites crawling under his skin. These conditions are also associated with high fevers and extreme alcohol withdrawal, often associated with visual hallucinations of insects.

People suffering from these conditions may scratch themselves to the extent of serious skin damage and bleeding, especially if they are delirious or intoxicated.

Treatment
If due to stimulant abuse, the primary treatment is to cease the use of stimulants. The chronic condition is treated much as other delusional disorders and schizophrenia. In the past, pimozide was the drug of choice when selecting from the typical antipsychotics.

Fictional accounts
An excellent fictional account of delusional parasitosis is given in the opening chapter of Philip K. Dick's novel A Scanner Darkly.