Delusional parasitosis in the elderly: a review and report of six cases from northern Finland.

A patient with delusional parasitosis has a strong conviction of being infested with parasites: for example, lice or worms. Such a patient is not satisfied with assurances or test results that no parasites are present, but is so convinced that he or she will go as far as to bring the parasites in "matchboxes" to a physician. Subjectively worried, the patient may try to pick the parasites out of the skin, causing cutaneous lesions and even ulcerations.