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Letters to the Editor / General Hospital Psychiatry 28 (2006) 78 – 87
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Delusional parasitosis or Ekbom syndrome: a case series
To the Editor,
1. Introduction
Delusional parasitosis (DP) is a neuropsychiatric syndrome in which the patient has the fixed delusion of
infestation by parasites such as lice and mites [1]. Although
several cases have been recorded since the end of the 19th
century, it was the Swedish psychiatrist Karl-Axel Ekbom
who first studied systematically the presenile syndrome of
delusional dermatozoid parasitic infestation in 1938 [2].
After a multitude of different names being used over the
years such as acarophobia or parasitophobic neurodermatitis,
Ekbom’s name has become the eponym attached to the
condition referred to later as DP [2–4]. One reason for this
nomenclature change was the recognition that DP is not a
phobia, i.e., an irrational fear of being infested by parasites,
but rather a delusional condition. Some still debate whether
the primary disorder in DP is a tactile or cenestesic
hallucination precipitating a secondary delusion [3–6].
Delusional parasitosis is considered a rare condition in
neuropsychiatric settings. It has been mainly described in
case reports or small case series [6–8]. Delusional parasitosis patients usually seek dermatological care since the
presenting symptoms include several skin lesions such as
excoriations from scratching. Thus, some surveys performed
with dermatologists suggested that DP may be more
common than previous thought [9,10].
In this study, we report a Brazilian series of DP derived
from a psychiatric clinic.
85
2. Methods
All patients with DP seen by the authors since 1995
were carefully reviewed. The diagnosis of DP was based
on a detailed clinical history. The psychiatric classification
was done according to the structured clinical interview
Mini International Neuropsychiatric Interview [11,12]. The
Mini-Mental Status Examination (MMSE) was also
applied to all patients [13]. In order to exclude secondary
causes of DP, an extensive laboratory evaluation was
performed, including complete blood cell count; liver,
renal and thyroid function tests; serum electrolytes and
glucose levels; vitamin B12, folate and iron studies;
urinalysis; serological study for syphilis. Neuroimaging
studies were available for all subjects. Demographic data
were also obtained.
3. Results
Ten patients with DP were identified. The demographic
and clinical characteristics of the patients are depicted in
Table 1. Of the 10 patients, seven were female, resulting
in a female-to-male ratio of 2.3:1. The age at first clinical
evaluation ranged from 67 to 81 years (mean ageFS.D.,
72.4F5.2). Duration of symptoms ranged from 6 months
to 3 years, with a mean (FS.D.) of 18.0 (F9.4) months.
The mean (FS.D.) time of follow-up of patients was 9.9
(F2.8) months.
The presenting dermatological signs were considerably
variable, including excoriations from scratching, lichenification, contact dermatitis to different topical products
applied. The bmatchbox sign,Q defined as the behavior of
bringing samples of the alleged parasites inside small
containers, was observed in just one patient (Case 9). The
phenomenon of folie à deux, i.e., shared delusion of
infestation by a partner, was not found in the present series.
Most patients were unmarried (widow, six; single, two)
or living alone (five). All had some clinical comorbidity,
mainly diabetes (four), hypertension (four) and thyroid
disease (three). None of the clinical illnesses could be
etiologically related to the diagnosis of DP. Five subjects
(50%) were diagnosed with a delusional disorder, a
primary psychotic category that cannot be attributed to
another major psychiatric disorder or physical illness
[14,15]. Two patients were diagnosed with major depression with psychotic symptoms, while another two with
dementia. One patient had a psychiatric background of
schizophrenia. The score in the MMSE was below the
expected value in three subjects (dementia, two; schizophrenia, three). Of note, three patients exhibited pathological findings on neuroimaging studies, marked cortical
atrophy (Cases 8 and 10) and multiple small infarctions of
subcortical white matter (Case 7), which were compatible
with their diagnosis.
All patients used some antipsychotic medication in low
dose: half typical (haloperidol or pimozide) and half atypical
86
Letters to the Editor / General Hospital Psychiatry 28 (2006) 78 – 87
Table 1
Demographic and clinical characteristics of the patients presenting with delusional parasitosis or Ekbom syndrome
Case
Sex
Age
(years)
Marital
status
Formal
education
(years)
Clinical
comorbidities
Psychiatric
diagnosis
(ICD-10 [14])
1
2
F
F
67
67
Widow
Widow
4
4
F22
F22
3
M
68
Widow
9
Hypertension
Hypertension,
diabetes
COPD
MMSE
[13] score
Treatment
(mg/day)
Outcome
(remission)
12
24
25
26
Risperidone (1)
Haloperidol (1.5)
Partial
Complete
6
26
Partial
F22
24
26
Hypertension
F32.2
12
24
F22
36
27
F01
6
17
Complete
F20
18
21
Haloperidol (2)
Partial
6
Hypertension,
Diabetes
Heart failure,
Hypothyroidism
Hypertension,
Diabetes
Hyperthyroidism
Haloperidol (1),
citalopram (20)
Olanzapine (5),
citalopram (20)
Olanzapine (2.5),
moclobemide (300)
Pimozide (2),
venlafaxine (75)
Risperidone (1)
4
F
69
Widow
5
Hyperthyroidism
5
M
69
Married
3
6
F
73
Single
7
7
F
74
Single
4
8
F
78
Widow
7
9
F
78
Widow
F22
24
26
Pimozide (2)
7
Heart failure
F00
18
18
Quetiapine (100),
rivastigmine (12)
No
improvement
Complete
10
M
81
Married
F32.3
Duration of
symptoms
(months)
Complete
Complete
Complete
COPD, chronic obstructive pulmonary disease.
(olanzapine, quetiapine or risperidone). Two patients developed acathisia (Cases 1 and 8) and one significant
syalorrhea (Case 3). No other serious adverse effect was
noticed. Four subjects used antidepressants, and the patient
with Alzheimer’s disease also used the acetylcholinesterase
inhibitor rivastigmine. Full clinical remission of the
delusional symptom was obtained in six subjects, while
four had partial or no improvement.
4. Discussion
Our DP cases were etiologically categorized into three
main groups. The first group (50%) comprised a primary
psychotic disorder referred to as a delusional disorder of the
somatic type according to the present classification schemes
[14,15]. The second group (30%) was composed of other
functional psychiatric disorders such as depression and
schizophrenia that exhibited typical symptoms of DP. The
last group (20%) included DP secondary to a physical or a
neurological illness. In the present study, two cases were
associated with dementia, one with Alzheimer’s disease and
the other with vascular dementia.
Several organic conditions have been causally related to
DP, including substance abuse, infectious and endocrine
disorders [16,17]. Although DP is known to occur in a wide
variety of these physical illnessess, previous studies also
found a primary psychotic disorder as the main cause of DP
[8,18,19]. In our series, thyroid disease, diabetes, cardiovascular and pulmonary diseases were considered comorbid
conditions rather than etiological factors. The advanced age
of the patients studied (mean ageFS.D., 72.4F5.2 years)
may explain this high occurrence of comorbidities.
As the mean duration of symptoms was 18 months, the
average age at onset of the symptoms in the present series
would be over 60 years. Associated with the female
preponderance, the high frequency of social isolation
represented by many patients living alone — these are
the typical features of DP according to the literature
[8–10,17,18]. Thus, our series is consistent with previous
studies performed in different genetic and sociocultural
backgrounds. This reinforces the view that DP may be a
stable diagnostic category across different cultures. Another
relevant point is that the present series came from a
psychiatric clinic, while others were derived mainly from
dermatological services [8–10,17].
The outcome was favorable in six patients (60%), while
the remaining subjects (40%) had partial improvement or no
improvement. This picture is also compatible with other
studies [8,17,18]. In our series, we did not have considerable
adverse effects either with typical or with atypical antipsychotics. We cannot draw any conclusion about the
clinical superiority of a specific antipsychotic. Until
recently, pimozide was the drug of choice in the treatment
of DP [17]. Based on a better side-effect profile and
tolerability, atypical antipsychotics have been prescribed to
DP patients. There are some case reports on the use of
atypical antipsychotics, such as risperidone, quetiapine,
olanzapine in DP, but controlled studies are lacking [8,20].
Such studies may be difficult to perform, as DP is an
uncommon and heterogeneous syndrome.
In conclusion, rather than a unique illness, DP is a
neuropsychiatric syndrome that can follow primary psychotic and depressive disorders, dementia or other organic
diseases. The typical patient is an elderly woman who is
Letters to the Editor / General Hospital Psychiatry 28 (2006) 78 – 87
unmarried or living alone. Clinicians should be alert to skin
lesions in these geriatric patients in order to exclude DP.
Rodrigo Nicolato, M.D.
Humberto Corrêa, M.D.
Department of Psychiatry, Faculty of Medicine
Federal University of Minas Gerais
Belo Horizonte 30130-100, Brazil
Marco A. Romano-Silva, M.D.
Department of Pharmacology
Institute of Biological Sciences
Federal University of Minas Gerais
Belo Horizonte 30130-100, Brazil
Antonio L. Teixeira Jr., M.D.
Department of Internal Medicine
Faculty of Medicine
Federal University of Minas Gerais
Belo Horizonte 30130-100, Brazil
E-mail address: [email protected]
doi:10.1016/j.genhosppsych.2005.08.008
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