A case of 'contagious delusional parasitosis' in an adult pair of twin sisters

In July 1992, a 50-year-old married woman, who was a hospital administrative clerk with an adult daughter, stated that, for over 5 years, she had been parasitised by 'small animals coming out from her skin'. While physical and microscopical examinations did not show either lesions or parasites on the skin, both the patient's medical history and the conviction with which she reported the phenomenon, led to a diagnosis of Delusory Parasitosis, a condition which has been well-defined for over 50 years and considered of prevailingly psychiatric competence. The patient was examined several times during the course of 6 years. She exhibited varying levels of anxiety, and brought with her different species of insects which she had captured 'when she saw them coming out of her skin'. In July 1998 the patient returned with her twin sister, who 'had been infected by her'. Indeed, she too 'had discharged various insects from her skin' for more than a year. The authors provide information on the response of this hallucinatory syndrome to therapy which, as in this case, appears to be resistant to treatment, unless appropriate psychoactive drugs are used.