Berks County Medical Society Medical Record Winter 2021 - 26

M e d i c a l R ec o r d F e a t u r e

Delusional Parasitosis in a Patient
with Dementia-related Psychosis
by Stacie Kerbel, Penn State University College of Medicine MPH Candidate and
Eduardo D. Epiridion, MD, DFAPA, CPE, Chairman of Psychiatry Department, Reading Hospital-Tower Health
ABSTRACT:
The patient presented with parasitic
delusions and cognitive impairment,
indicating a diagnosis of dementia-relate
psychosis, with Alzheimer's dementia (AD)
as the form of dementia and delusional
parasitosis as the form of psychosis. The
patient was treated with risperidone,
an antipsychotic which is in a class of
medications that has demonstrated success
when treating both delusional parasitosis
and dementia and delusional parasitosis in
patients with specifically AD. Delusional
parasitosis is rarely experienced by patients
with AD and there are few case reports
indicating this diagnosis.
INTRODUCTION:
Approximately 90% of patients
diagnosed with dementia will experience a
behavioral and psychological symptom of
the disease, including psychosis, aggression,
agitation, or depression.1 The relationship
between the dementia and the symptoms
may be due to both neurochemical
changes and psychological and social
changes.1 Degenerations in the frontal and
mesotemporal areas of the brain have been
reported to be associated with psychosis.1
The relationship between AD, the most
common form of dementia and psychosis
has previously been established.2 Patients
may experience delusions, hallucinations,
and misidentification.2 One study
indicated that reduction of the brain's
lobes, especially the frontal lobe may be
associated with delusion.3 Other studies
have indicated that delusions are the result
of decreases in lateral ventricle size and to
basal ganglia calcification.2
AD is the most commonly reported
form of dementia and the pathophysiology
relates to a loss of neurons.1 While there are
reports of patients experiencing delusional

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parasitosis secondary to a diagnosis of
dementia, there are relatively few reports
of AD patients experiencing this delusion.
Delusional parasitosis is seen as the false
belief that an individual is infected with
parasites or insects.4 It has been found
that elderly women experience this
phenomenon at a greater rate.5
CASE PRESENTATION:
The patient is a 78-year-old married
black male who had no prior psychiatric
history or prior psychiatric hospitalizations.
He was admitted to the medical floor
because of worsening confusion and
agitation. He demonstrated worsening
cognitive impairment with problems in
his executive level of functioning. He
developed the onset of memory problems
and was diagnosed with AD 2 years prior
to this hospitalization. He was under the
care of a neurologist for the past year;
however, his cognitive impairment had
steadily declined. He also demonstrated
referential and paranoid thoughts over the
prior two months. The patient had begun
to make allegations that his daughter-inlaw was conspiring to hurt him. He also
alleged that she was stealing his money,
whenever he left the house. This led to
confrontations with his son and daughterin-law. Approximately a month prior
to this admission, the patient started
to feel crawling sensations on his lower
extremities. He became convinced that
there were bedbugs in his bed. His family
bought him a new mattress; however, the
crawling sensations persisted. He started
using a razor and shaved off the hair from
his lower extremities which resulted in
lacerations. He later became convinced
that the bedbugs were hiding underneath
the wound scabs and shaved them off with
resulting infection and bleeding.

He was cooperative during the
admission psychiatric evaluation. He
scored a 22/30 on the Mini-Mental Status
Examination (MMSE). He pointed to the
" bedbugs " on his leg and attempted to
convince the staff that they were present.
He was started on risperidone 0.5 mg at
bedtime. The laboratory work-up including
his complete blood count, urinalysis, urine
toxicology screen, and blood electrolytes
were within normal limits. He continued
his psychiatric treatment and was later
transferred to a dementia unit of a
nursing home where somatic delusions
completely resolved. The patient continued
to be treated with risperidone following
resolution of delusions.
DISCUSSION:
Structural magnetic resonance imaging
scans (MRI) indicate that for late onset
AD there is atrophy in the medial temporal
lobe, including the para-hypothalamus
and amygdala.6 In early-onset AD the
brain atrophy is seen more posteriorly,
involving the posterior cortex, occipital
lobe, posterior cingulate, and precuneus.6
Additionally, atrophy in the hippocampus
and entorhinal cortex is associated with
memory decline and puts people at
an increased risk of AD.6 The patient's
diagnosis of AD was supported by his low
score on the MMSE and structural changes
seen on his MRI.
One-third of patients with AD
experience psychotic symptoms that
may decrease quality of life, increase
aggregation, hospitalizations, burden of
care, and mortality.7 Patients with AD
experience delusions that tend to be
paranoid type, non-bizarre and simple.8
They may involve the belief that a person
is stealing from them, they are in danger,
others are planning to harm them, their
spouse or caregiver is an imposter, their


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Berks County Medical Society Medical Record Winter 2021

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