Delusional parasitosis as 'folie à trois'

Delusional parasitosis can apparently run in families. Three out of 9 members of a German family were fully convinced that their skin had been invaded by 'tiny running animals' even though there was no physical evidence of any infestation. Although the family was reluctant to be injected with neuroleptic drugs as this would have been an acknowledgement that their symptoms were in fact of psychological origin, they eventually agreed to be treated. When last contacted, 3 years after diagnosis, they still believed in the existence of the parasites but admitted that some of their symptoms had improved.