Delusion of parasitosis is a form of monosymptomatic hypochondriacal psychosis (MHP)1 that is classified as a somatoform delusional disorder according to Diagnostic and Statistical Manual of Mental Disorders (4th edn; DSM-IV). Individuals with delusion of parasitosis have an intense conviction that small living organs such as worms or insects infest the skin even though there is no confirming evidence. This condition is likely to occur in presenile and senile women.2 During the past two decades, pimozide has been the first-line treatment for delusion of parasitosis and MHP.1,3,4 Sulpiride, which has a relatively low incidence of extrapyramidal and cardiac symptoms, is often prescribed to the elderly. To date only one case report described successful treatment of delusion of parasitosis with sulpiride.5 We report two patients with delusion of parasitosis who responded dramatically to low doses of sulpiride.

Ms A, an 84-year-old woman, was referred to Department of Psychiatry at Shinshu University School of Medicine by her internist because of the patient's intense conviction that many worms were crawling out of her skin. The patient was under treatment for hypertension and diabetes mellitus. At presentation she insisted that tiny worms laid eggs everywhere in the wall, on the floor, and in her clothes, and that numerous worms were attached to her skin and stinging her. Her family reported that this belief in a worm infestation had persisted for 12 months, and that she cleaned the house and clothes all day long to eradicate the worms. Ms A and her family denied any previous history of psychiatric illness. There was no evidence of dementia; on the revised Hasegawa Dementia Scale she scored 27 of 30, and her IQ estimated by the Wechsler Adult Intelligence Scale-Revised block pattern test was 100. Magnetic resonance imaging demonstrated signs of multiple small cerebral infarctions in the basal ganglia and thalamus.

Medication with sulpiride at 50 mg/day improved her delusion within weeks. She reported that there were few worms and she could distinguish worms from trash. Her family also reported that she stopped her excessive cleaning. Sulpiride administration was maintained at 40 mg/day thereafter, and she remained free from symptoms of delusions for approximately 3 years, except for an occasion when she stopped taking sulpiride on her own. Her worm delusion reappeared with discontinuation of sulpiride, then disappeared on resumption of medication.

Mr B, a 71-year-old man, was referred to Department of Psychiatry at Shinshu University School of Medicine for persistent delusions of being infested by many worms. He had undergone hemodialysis twice a week due to chronic renal failure since the age of 55 years. At the age of 70 years he complained of itching of the head and trunk, and had also developed an abnormal sensation of worm bites in his head. He visited the dermatologist, and complained that many living worms were in his head, and that these worms came out to sting him. He also brought an amount of scales and dandruff that were alleged to be worms. Initially he was prescribed an external steroid preparation and oral diazepam at 4 mg/day by the dermatologist but the symptoms did not improve, and he was then referred to our department. At presentation his memory was intact and he was fully oriented. He expressed some displeasure about being referred to a psychiatrist because he was confident that worms were objectively present and that actual bites were occurring. Medication was started with sulpiride at 50 mg/day and maintained at 100 mg/day. Improvement occurred within weeks; the patient reported that the worms had nearly disappeared and that he felt better. He has rarely complained of worms for approximately 2 years, and continues to regularly consult our clinic.

Delusional parasitosis occurs in a wide variety of illnesses, involving both physical and psychotic disorders. In the present two cases delusions of parasites developed associated with physical conditions, such as diabetes mellitus and multiple cerebral infarctions in the first patient, and chronic renal failure in the second patient. These conditions are known to be involved in the development of delusion of parasitosis, due to the potential of these disorders to alter tactile perception.6

Since the description by Riding and Munro4 pimozide has been the first-line treatment for MHP and delusion of parasitosis. However, several case studies describe successful treatment of MHP with other psychotropic agents (e.g. haloperidol, trifluoperazine, and tricyclic antidepressants).7,8 Recently, risperidone, a novel atypical antipsychotic agent that potently blocks both D2 and 5-HT2 receptors, is also effective in the treatment of MHP.9,10 De Leon et al. discussed the importance of 5-HT2 antagonistic actions in therapeutic effects on MHP.10 Sulpirides are highly selective D2-receptor blockers, and have little 5-HT2 antagonistic action. The present report has documented the effectivness of a small dose of sulpiride in the treatment for MHP. We consider that the D2 blockade action may play an important role in the therapeutic benefit for the present patients. We consider that sulpiride may be an another agent for the treatment of MHP in the elderly.


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  2. References
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    Munro A. Monosymptomatic hypochondriacal psychosis. Br. J. Psychiatry 1988; 153 (Suppl. 2): 3740.
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    Takahashi T, Tamaru T, Imai J et al. Pathology in senile patients with abnormal body sensation. Psychogeriatrics 2001; 1: 139142.
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    Riding J, Munro A. Pimozide in the treatment of monosymptomatic hypochondriacal psychosis. Acta Psychiatr. Scand. 1975; 52: 2330.
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    Amakusa T. Clinical experiences of sulpiride to cenestopathia. Seishin Igaku 1974; 16: 502503 (in Japanese).
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    De Leon J, Antelo RE, Simpson G. Delusion of parasitosis or chronic tactile hallucinosis: Hypothesis about their brain physiopathology. Compr. Psychiatry 1992; 33: 2533.
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    De Leon OA, Furmaga KM, Canterbury AL, Bailey LG. Risperidone in the treatment of delusions of infestation. Int. J. Psychiatry Med. 1997; 27: 403409.