Delusional parasitosis of face in a factory worker.

Delusional parasitosis is a form of monohypochondriacal psychosis, a condition sometimes encountered in psychiatric or dermatological clinical practice. The exact etiology and outcome of this condition is not well known. A patient with delusional parasitosis of face who responded to aripiprazole is described.

Delusional parasitosis, a term coined by Wilson and Miller,[1] is an uncommon condition characterized by the single hypochondriacal, delusional system that the patient is infested with insects. Munro[2] and Bhatia et al.[3] described the few largest series and highlighted its diagnostic criteria. This condition has occasionally been found to be associated with systemic conditions like pellagra, vitamin B12 deficiency, cerebrovascular disease and temporal lobe epilepsy, and leprosy.[4-7] We report a case of delusional parasitosis affecting face, which also responded to a second-generation antipsychotic, aripiprazole.

CASE REPORT

The patient was a 36-year-old married male working in a garment factory as a security guard. He was high school passed, earning about ‘10,000/- per month. He was living with wife and two children in his one-room own house. There were no familial, financial, or occupational stresses. He presented with a 7-month history of itching on the face, which he attributed to infestation by insects. He had himself used different antiseptics for killing or removing insects but felt no relief. On examination by a dermatologist, he was found to have no evidence of infestation. The patient had also brought excoriated skin specimen in a matchbox as evidence of infestation (matchbox sign). On his request, the histopathologic examination of the specimen was done, which revealed excoriated skin scales and no parasites. The marks due to scratching were present on the side of face. He was told that it is a disease that requires assessment and treatment from psychiatry outpatient department.

The detailed psychiatric workup revealed preoccupation with the complaint that he is being infested with insects over the face. There had been a no change in the symptom since the onset. He said that that he was unaware of the source of infestation but believed that it was not related to his occupation or accommodation as no other person from there had similar complaints. Due to this infestation, he had developed anxiety and sleeplessness and was unable to do his job efficiently. He did not believe the suggestion of his friends and wife that there is no such infestation with insects. He was finally brought by his wife to the hospital. Detailed systemic examination including neurological examination and relevant investigations did not reveal any abnormality. There no past history of any chronic psychiatric disorder, chronic physical disease, or drug abuse. Family history was also normal. Mental state examination revealed a middle-aged man of endomorphic build. Psychomotor activity and speech were normal. There was no perceptual abnormality. He was anxious. Thinking revealed the presence of delusions of being infested by small insects. No other psychopathology was detected. Higher mental functions were normal.

The patient was started on aripiprazole 10 mg/day, which was gradually increased to 20 mg/day in 3 weeks time. There was complete remission, and on following him up for 6 months, he did not develop the delusion again.

DISCUSSION

In our patient, itching on face along with fear of being infested with worms seems to have triggered off the delusion of parasitosis. The exact mechanism of the evolution of the delusional system in this disorder is not known. One hypothesis is that these patients suffer a profound breakdown in their ability to discriminate between normal and abnormal somatic perceptions and the delusion may be mediated by endogenous dysfunction in the limbic system. This dysfunction may be the result of a pathological overactivity of the dopaminergic system, as evidenced by the efficacy of the specific dopamine antagonist, pimozide.[238] The histopathology of skin biopsy and specimen brought by the patients show dermatitis, excoriation, ulceration, or inflammation, but no parasites.[9] In the present case also, there were no parasites seen, but it showed matchbox sign classically reported with this disorder. There are reports mentioning the usefulness of aripiprazole in the treatment of delusional parasitosis.[1011] Aripiprazole has a partial agonist activity at dopamine D2 and serotonin 5-HT1A receptors and has a favorable side-effect profile relative to other antipsychotics, which may be a particular benefit in primary delusional parasitosis as these patients require long-term treatment and are often reluctant to consider antipsychotic treatment and have poor compliance due to the adverse effects of medication.[11] Aripiprazole has a long half-life (about 60 h) compared with other oral antipsychotics,[12] which means that occasional missed doses are less likely to affect the clinical outcome. Consequently, aripiprazole may be particularly useful when intermittent adherence to medication is a problem, a situation often encountered in primary delusional parasitosis.[10] The presentation of delusional parasitosis with face being affected and complete response with treatment has been rarely reported.[1] Some authors have found trigeminal nerve roots’ affliction as the cause of parasitosis, so magnetic resonance imaging of the area would be informative.[13] The present case was followed up for 6 months and did not develop the delusion again. The exact duration of treatment is not known, but it is believed that these patients usually require long-term treatment because relapse rate is high on stopping the treatment.[14]