Discussion
Treatment of delusional disorder can be particularly
challenging because currently no guidelines exist to guide the use of
pharmacotherapy in this disorder. To our knowledge, this is the first
report demonstrating that delusional disorder, persecutory type, is
successfully treated with lurasidone. A number of properties make
lurasidone an appropriate choice for the treatment of delusional
disorder in our patient, and a potentially important addition to the
options for treatment in other patients with delusional disorder.
Lurasidone is associated with minimal weight gain and no clinically
significant alterations in glucose, lipids, or prolactin [9]. This is of
particular importance for our patient, who has several metabolic
risk factors, including obesity and elevated triglycerides, and who
will likely require long-term therapy. Additionally, since our patient
has a history of poor medication adherence, lurasidone’s once daily
dosing is appealing [10]. Lurasidone does carry a similar risk for
extrapyramidal side effects as risperidone (O.R. 2.46 (CI 1.55-3.72)
and 2.09 (CI 1.54-2.78), respectively), [11]but fortunately, our patient
did not develop any extrapyramidal symptoms during her hospital
stay.
Lurasidone acts as a partial agonist at 5-HT1A receptors and an
antagonist at 5-HT7
receptors, which results in improvement in
cognitive performance and a significant reduction in depression[12].
This receptor profile may be particularly beneficial in patients with
delusional disorder. Previous reports have proposed that serotonergic
dysfunction may be involved in the pathophysiology of Delusional
Disorder, Somatic Type (DDST) based on reports of successful
treatment with antidepressants [13,14]. Although no reports have
addressed the role of serotonergic dysfunction in all other types of
delusional disorder, comorbid mood disorder is estimated to occur in
32 to 53 percent of all delusional disorder patients[15-17]. Depressed
mood and negative cognition are frequently associated with paranoid
thinking [18]. A recent study demonstrated that in patients with
non affective psychosis (schizophrenia, schizoaffective disorder,
and delusional disorder), depressed mood and negative ideas about
the self predicted the strength of persecutory delusions. It has been
suggested that treatment of emotional dysfunction may lead to
reductions in current psychotic experiences [18]. Thus, lurasidone
may provide benefit in the treatment of delusional disorder both
through its possible effects on depression and cognition in addition
to its antipsychotic properties. Further work on the role of serotonin
in delusional disorder should be pursued; given lurasidone’s unique
serotonin receptor profile, systematic studies may find that this
antipsychotic could be particularly useful in delusional disorder.
In conclusion, this case demonstrates that delusional disorder can
be successfully treated with lurasidone. Further research is warranted
to support the potential benefits of lurasidone for the treatment of
delusional disorder, and while we hope high quality randomized
controlled trials can be conducted to guide treatment, in the interim
we hope case reports such as this will allow clinicians some support in
treatment decisions for this difficult to treat illness.