Delusional parasitosis.

Skin-related delusional diseases with unspecific status and/or status without dermatological findings, among others ‘dermatological delusion’, are categorized as ‘delusional disorders’ (ICD-10: F 22.0; DSM-IV 297.1). A delusional disorder is diagnosed when (according to DSM-IV) the following criteria are fulfilled: A. Non-bizarre delusions (i.e. regarding situations not out of the realm of possibility, e.g. being pursued, poisoned, infected or attaining an illness) of at least 1 month’s duration B. Criterion A for schizophrenia has never been met (i.e. among others, lack of hallucinations, disorganized speech, or behavior – so-called negative symptoms; tactile hallucinations may be present if related to the delusional theme) C. Apart from the primary and secondary effects of the delusions, functioning is not markedly impaired and behavior is not obviously bizarre or out of the ordinary D. If mood episodes have occurred concurrently with delusions, their total duration has been brief relative to the duration of the delusional periods E. The disturbance is not due to direct physiological effects of a substance (e.g. drug, medication) or a general medical condition The type of delusion describes its contents and/or orientation (erotomanic, grandiose, jealous, persecutory). A delusion pertaining to skin can be categorized as a body-related delusion (DSM-IV: ‘The delusion that the individual has a physical defect or a medical disease factor’). Delusional parasitosis, also known as Ekbom’s syndrome [AitAmeur et al., 2000], can be considered a ‘classical’ skin-related delusional disorder. The generic term ‘chronic tactile hallucinosis’ which is still used in publications is outdated: The skin symptoms experienced (‘hallucinated’) by the patient, ranging from itching to ‘crawling of animals on the skin’, are related exclusively to the content of the delusion, i.e. the uncorrectable conviction that the skin is infested with parasites. It is not infrequent that patients strive to prove their illness. Particles of skin or dirt are collected and interpreted as parasites, unspecific changes of the skin are seen as consequences of a parasite-related illness. Attempts of self-healing, such as repeated washing and disinfecting of the skin, can cause secondary skin phenomena [for recent reviews see Bhatia et al., 2000; Koo and Lee, 2001; Freudenmann, 2002].