Delusional infestation: a case series from a university dermatology center in São Paulo, Brazil

Monosymptomatic hypochondriac psychosis (MHP) patients present with a delusional ideation that revolves around one particular hypochondriac concern. Delusional infestation is the most common type of MHP seen by the dermatologist.

This study was designed to retrospectively investigate a group of patients with delusions of infestation seen in an academic medical center in São Paulo, Brazil.

A retrospective study of patients presenting with delusional infestation between 2007 and 2014 was conducted. Records were reviewed to study personal data, symptoms, and treatments.

Thirty patients were studied (22 female, eight male). Their mean age was 58 years in men and 60 years in women. Twenty-four patients spent most of their time at home (i.e. they were housewives, retired, or unemployed). The duration of disease varied from 3 months to 20 years. Fifteen patients brought in fragments of material that they believed to be parasites ("specimen sign"). Treatment consisted of the antipsychotic drugs pimozide (1-6 mg/d) or olanzapine (5-10 mg/d). Three patients did not return for follow-up. Follow-up varying from 2 months to 7 years was recorded in 24 patients. Two patients were treated with other psychoactive drugs prescribed by psychiatrists for additional psychiatric diagnoses. Control of symptoms was achieved in the majority of patients who underwent adequate follow-up.

Delusional infestation is an extremely chronic disease. Attempts to discontinue treatment in those patients in whom a lengthy follow-up was performed inevitably resulted in symptom relapses.