Delusional infestation: A clinical profile

Abstract

Objective

Delusional infestation or delusional parasitosis is a form of monodelusional disorder, a condition sometimes encountered in psychiatric or primary care practice. The outcome of this condition is good when compliance can be ensured.

Patients and methods

In the present study, a series of 50 consecutive cases of delusional infestation is reported.

Results

A majority of cases (94%) had insidious onset. The duration of symptoms in all but 3 cases was 6 months or more. Twenty-eight cases presented with a delusion of infestation by insects over the body and 20 cases with a delusion of insects crawling over the scalp. Two cases had associated diabetes mellitus, 3 cases had leprosy, 2 cases had dementia, 5 cases had depression, and 4 cases presented with trichotillomania. Among the second generation antipsychotics, risperidone was used in 12 cases, olanzapine in 9 cases, amisulpride in 7 cases, etc. Thirty-four cases (68%) showed complete remission while receiving pharmacotherapy, 13 cases showed partial improvement, and 3 cases did not respond to treatment.

Conclusions

The study demonstrates the utility of second generation antipsychotics in the treatment of this disorder. Further studies are warranted to study the treatment and outcome of this important psychiatric disorder.

Introduction

Since the publication of the article entitled: “Delusion of Parasitosis” by Gould and Gragg (1976), increased interest in this condition has been engendered in the psychiatric literature. Delusional parasitosis was first described by Thibierge (1894) and Perrin (1896). Various terms used in the literature to refer to delusional infestation or delusional parasitosis include Wittmaack-Ekbom syndrome, Ekbom syndrome, acarophobia, parasitophobia, dermatophobia, entomophobia, parasitophobic dermatitis, delusory parasitosis but the names ending with “-phobia” are misleading as there is no anxiety disorder (Munro, 1978, Berrios, 1985, Fredenmann and Lepping, 2009). In ICD-10 (WHO, 1993), it meets the criteria of persistent delusional disorder whereas in DSM-IV-TR (APA, 1994), it may be classified under delusional disorder, somatic type.

Delusional parasitosis, a term introduced by Wilson and Miller in 1946, is characterized by the single hypochondriacal, delusional system that the patient is infested with insects. It is one of the most common presentations of monohypochondriacal psychosis which occurs in absence of any other psychiatric illness (Munro and Chmara, 1982). Delusional parasitosis has also been described as primary (not due to any other underlying psychiatric or physical disorder) or as secondary to dementia, psychosis (Lyell, 1983, Bhatia et al., 1993, Trabert, 1995, Ghaffari-Nejad and Toofani, 2006, Duggal and Singh, 2010), and medical conditions such as vitamin B12 deficiency, pellagra, severe renal disease, diabetes mellitus, multiple sclerosis, hepatitis, and leprosy (Berrios, 1985, de Lekon et al., 1992, Shome et al., 1993, Bhatia et al., 1992, Bhatia et al., 1993, Bhatia et al., 1996a, Bhatia et al., 1996b) or drug-induced (Swick and Walling, 2005, Steinert and Studemund, 2006, Lopez et al., 2010). It can also occur as a folie a deux or folie a trios (Trabert, 1995, Bhatia et al., 1996a, Bhatia et al., 1996b) as well as proxy (Nel et al., 2010). The present study describes a series of 50 cases of delusional infestation seen over a period of 8 years.