Berks County Medical Society Medical Record Winter 2021 - 27

house is not their home, family members
are planning on abandoning them, and
other delusions related to suspiciousness
and paranoia.8 Common delusions
experienced by patients with AD may
also be related to theft or infidelity.2,9 This
patient displayed accusatory behavior
and suspicions, a behavior associated
with delusions in patients with AD.2
Patients with AD may also hallucinate
and experience misidentification.2
The hallucinations are usually visual
hallucinations of strangers and occur less
frequently than delusions.2,9 Additionally,
misidentification is composed of four
syndromes, the belief that a another
person is in their house based on probable
misidentification, misidentification
of their own reflection in the mirror,
misidentification of events on television as
being real, and misidentification of other
people such that they may believe that their
relative has been replaced.2 For those with
AD and psychosis, the cognitive decline is
more rapid than those without psychosis,
however, the morbidity of the patients
remains the same.8
Delusional parasitosis is a rare disorder
and considered by the Diagnostic and
Statistical Manual of Mental Disorders,
Fifth Edition (DSM-V), as a delusional
disorder with a somatic subtype.3 Among
all delusional disorders, there is a 0.05% to
0.1% prevalence of delusional parasitosis
diagnoses.3 These disorders can be either
the primary disorder or can be secondary
to another disorder.3 In order to be
diagnosed with delusional parasitosis
one needs to rule out an organic cause
to the perceived infestation.10 Ekbom
believed that delusions are the result of
true cutaneous sensations.10 For those
with delusional parasitosis they will report
that they have had a significant history of
having inept, uncaring, uninterested, and
ignorant physicians.11 The patients will
often leave a rather rigid, antagonistic,
distant and demanding first impression.11
They will also bring jars and containers
filled with the parasites they perceive.11
Additionally, they may report the tactile
sensation of feeling bugs crawling on their
skin. Similarly, as the patient described in
this case report, people have used extreme
methods to remove the parasites from
their skin.12 The patient reported removing

the perceived parasites with a razor and
then continuing to remove parasites from
the lesions he formed, leading to the
formation of infection. The combination
of delusional parasitosis and AD creates a
diagnosis of dementia-related psychosis,
specifically with AD being the form of
dementia and delusional parasitosis as the
form of psychosis. Because the man had no
previous psychiatric history, it is believed
that the delusions are secondary to AD.
Delusional parasitosis is uncommon
in patients with dementia. Patients
with both disorders perform worse on
cognitive testing and demonstrate more
frontal lobe and executive deficits than
those without delusions.5 In those people
with cognitive impairment, abnormal
skin sensations of senile pruritus, may
lead to the development of delusional
infestation.10 While there have been
few reports of people with AD and
delusional parasitosis, treatment has been
reported. One patient was treated with 0.5
milligrams daily of risperidone and five
milligrams daily of donepezil.5 When the
amount of risperidone was increased to two
milligrams, the patient's delusions resolved.
This same antipsychotic was used in the
patient in this case report intending that
0.5 milligrams of risperidone daily before
bedtime may resolve the delusions. Another
case report described a patient treated with
8 mg of pimozide daily, with resolution of
symptoms. In addition, treatment has been
reported for delusional parasitosis with
dementia without an official diagnosis of
AD.13 That study reported that for people
with primary forms of delusional parasitosis
and secondary forms of the delusion, the
medication pimozide is an appropriate
medication for the delusions.13 Thus, once
again indicating that antipsychotics were
an appropriate class of medication for the
patient reported.
CONCLUSION:
	 The patient presented with parasitic
delusions and cognitive impairment. For
the reasons discussed above, it is believed
that this 78 year-old-man was experiencing
delusional parasitosis secondary to his AD
diagnosis. The patient was treated with
risperidone, which has been previously
used to decrease parasitic delusions in
those with AD, suggesting that it was an

appropriate treatment for the patient to
decrease the presence of his delusions.
The prevalence of delusional parasitosis in
patients with AD is quite uncommon with
few reports in the medical literature. Thus,
this case report may be used in the future
to further understand this phenomenon.
 
Marcinkowska M, Śniecikowska J, Fajkis N, Paśko P,
Franczyk W, Kołaczkowski M: Management of dementiarelated psychosis, agitation and aggression: a review
of the pharmacology and clinical effects of potential
drug candidates. CNS Drugs. 2020, 34(3):243-268.
10.1007/s40263-020-00707-7

1.

Bondareff W: Neuropathology of psychotic symptoms
in alzheimer's disease. Int Psychogeriatrics. 1997,
8(S3):233-237. 10.1017/S1041610297003402

2.

Qian W, Schweizer TA, Churchill NW, et al: Gray
matter changes associated with the development of
delusions in alzheimer disease. Am J Geriatr Psychiatry.
2019, 27(5):490-498. 10.1016/j.jagp.2018.09.016

3.

D'Auria A, Wiseman T, Varghese A, Espiridion ED:
Refractory delusional parasitosis in a 70-year-old woman.
Cureus. 2018, 10(8). 10.7759/cureus.3120

4.

Duggal H, Singh I: Delusional parasitosis as a
presenting feature of dementia. J Neuropsychiatry Clin
Neurosci. 2010, 22(1):123.e11-123.e12. 10.1176/
jnp.2010.22.1.123.e11

5.

Reitz C, Mayeux R: Alzheimer disease: epidemiology,
diagnostic criteria, risk factors and biomarkers. Biochem
Pharmacol. 2014, 88(4):640-651. 10.1016/J.
BCP.2013.12.024

6.

rasad KM: Delusions in alzheimer disease: what
researchers should not forget. Am J Geriatr Psychiatry.
2019, 27(5):499-501. 10.1016/j.jagp.2018.12.034

7.

Schneider LS, Dagerman KS: Psychosis of alzheimer's
disease: clinical characteristics and history. In: Journal of
Psychiatric Research. Vol 38. Elsevier Ltd; 2004, 105111. 10.1016/S0022-3956(03)00092-X

8.

Ballard CG, Saad K, Patel A, et al: The prevalence
and phenomenology of psychotic symptoms in dementia
sufferers. Int J Geriatr Psychiatry. 1995, 10(6):477485. 10.1002/gps.930100607

9.

Renvoize EB, Kent J, Klar HM: Delusional infestation
and dementia: a case report. Br J Psychiatry. 1987,
150(MAR.):403-405. 10.1192/bjp.150.3.403
10.

11.
Huber M, Kirchler E, Karner M, Pycha R: Delusional
parasitosis and the dopamine transporter. A new insight
of etiology? Med Hypotheses. 2007, 68(6):1351-1358.
10.1016/j.mehy.2006.07.061
12.
Knapp B, Tito D, Espiridion ED: Delusional
parasitosis in a patient with alcohol-induced psychotic
disorder. Cureus. 2019, 11(3). 10.7759/cureus.4344
13.
Bhatia MS, Jagawat T, Choudhary S: Delusional
parasitosis: a clinical profile. Int J Psychiatry Med.
2000, 30(1):83-91. 10.2190/BBDT-CGB9-BB3L8HM3

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Berks County Medical Society Medical Record Winter 2021

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