Delusional parasitosis: Report on response to olanzapine in a case series of 04 patients

ABSTRACT

Delusional parasitosis (DP) is a type of delusional disorder which is characterised by single hypochondriacal delusion in which patient believes that he/she is infested with insects/worms/parasite. The authors present a case series of four cases of DP which were assessed in the outpatient department of psychiatry of a tertiary care hospital in Western Maharashtra. The patients with DP were predominantly women around 50 years of age who were treated successfully with Tab Olanzapine and psychotherapy with favourable response.

Delusional parasitosis is an infrequent psychocutaneous disorder arising as a result of bidirectional interaction between mind and skin and thus disorder of one may influence aggravation or precipitation of symptoms of the other.[1] In this disorder, patients develop an unsubstantiated belief of skin being infested with a parasite. These disorders are conventionally recognised as delusional parasitosis (DP), as named initially by Wilson and Miller in 1946.[2] These are also termed as Ekbom syndrome after a Swedish psychiatrist Karl Axel Ekbom, who created the designation presenile dermatozoic delusion or ‘delusional of animal life in skin’.[3]

The disorder is characterised by false belief of skin being infested by parasites despite no visible parasite or skin lesion and repeated negative clinical examination or reassurance by the clinicians. This unreasonable belief is often accompanied with tactile hallucinations like experiencing movements under the skin, pain or tingling sensation.[4] Frequently, patients report to dermatologists with features of excoriation, skin bruises and other skin damages which have been their futile attempts to remove the parasites. Certain patients ‘bring the parasite’ (which are usually pieces of hair, fibre, cloth, skin debris, etc.) for examination to doctors (‘match-box sign’).[5]

DP is sometimes shared by more than one person in the same family (folie à deux). The person who initially harbours this delusion is the ‘Inducer’ and is the one who persuades others of his or her delusion till it becomes a shared belief. It is seen that treatment of inducer usually leads to resolution of belief in other affected family members. There are studies reporting frequencies of this ranging from 8% to 49%.[6]

DP can be primary where the patients have belief of being infested with parasites without any other medical or psychiatric disorders. As this delusional ideation revolves around only one particular hypochondriacal concern, these patients are said to suffer from monosymptomatic hypochondriacal psychosis (MHP).[7] It could be secondary to psychiatric disorders like schizophrenia, depression, dementia, anxiety and phobia whereas organic delusional parasitosis occurs secondary to illnesses like hypothyroidism, Vitamin B 12 deficiency, diabetes, cardiovascular disorders, cocaine intoxication, HIV and allergies.[8,9]

According to DSM—5, the lifetime prevalence of delusional disorders is 0.2%. A population-based cohort reported overall age and sex-adjusted incidence of 1.9 per 100,000 person-years from 1976 through 2010 indicating it to be a rare disease.[10] Reports from India suggest that it has a prevalence estimate of 0.5% in a clinical sample of psychiatry patients. Systematic research into treatment of DP is lacking. Available treatment related data is from either case reports or case series. Antipsychotics, both atypical and typical, are considered the drug of choice.[11]

Case 1

A 52-year-old married female, not formally educated, with no past or family history of psychiatric illness or medical comorbidities was referred for psychiatric evaluation by dermatologist in July 2021 with complaint of being infested by worms inside her body since past 04 months.

Onset of symptoms was in April 2021 after a few worms fell on her while she was cleaning grains. Although she removed all the worms carefully, within a few minutes, she had sensations as if something is crawling on her thighs and genitalia. She cleaned those areas and changed her clothes, after which she felt relieved. Over the next few days, she started having regular itching around genitalia and anal region and had to repeatedly scratch for relief. Within the next couple of weeks, she started experiencing uncomfortable, crawling sensation over abdomen which progressed over next 2 months and involved almost the whole body. Once, she noticed abraded skin near her genitalia and concluded that it was due to the worm bite. Over the next month, having noticed multiple such abrasions, which were actually being caused due to repeated scratching, she started believing that worms had moved from her anal region to inside her body and were now crawling under her skin. She used multiple home remedies, bathed frequently, changed her clothes many times in a day with the purpose of getting rid of them and preventing further spread. Finally, she consulted dermatologist but despite repeated reassurances and frequent change of medications she continued to be symptomatic. Due to lack of consonance in her symptoms and physical findings, she was referred to psychiatry OPD.

Evaluation revealed delusions and somatic hallucinations relevant haematological and biochemical investigations and NCCT Brain were normal.

She was diagnosed as a case of delusional parasitosis in view of fixed firm belief of being infested by worms despite normal clinical examination and investigations. She was started on Tab Olanzapine 5 mg/day which was increased to 15 mg/day over a period of 2 months along with supportive psychotherapy, building patient trust and CBT aimed at questioning the belief and reduction of distress due to symptoms. She was also managed by dermatologist for chronic dermatitis for repeated itching. Her symptoms gradually ameliorated over a course of 3–4 months and she is asymptomatic at present.

Case 2

A 47-year-old housewife, educated upto 12^th standard, with no past or family history of psychiatric illness, with primary hypertension since past 2 years, was brought to psychiatry OPD by her son after being referred from medicine in September 2021 with complaints of worms crawling inside her body since past 5 months.

She was apparently well till May 2021 when on one occasion she forgot to wash her menstrual bleed prior to going to sleep. At night, she felt some crawling sensation over her thighs and genitalia. She washed those parts and got relieved. Two days later, she had similar crawling sensation around her anal area. She thought it was probably some worm and cleaned off the area with Dettol and slept off. Gradually, over the next 4 months, she was having this sensation repeatedly. She attributed this to infestation by the worms and recounted that these are the worms from that night which have now reached her abdomen via anal route and had laid eggs. She sought consultations from physicians but had no relief. These sensations were further felt in under her scalp which she believed was due to movement of worms from her abdomen to brain. During this time, she also had frequent indigestion which she believed was due to those worms. This led to repeated consultations in medical OPD, from where she was referred for psychiatry consultation.

Based on clinical evaluation and MSE findings, she was diagnosed as a case of delusional parasitosis. Her baseline investigations including neuroimaging were normal. She was treated with Tab Olanzapine 5 mg which was increased to 20 mg over a period of 2 months and CBT with gradual reduction in crawling sensation by 60–70%. She attributed the improvement in her symptoms to medications killing the bigger worms with residual symptoms being due to remnant smaller worms. Over a period of 3–4 months, her belief of infestation by parasites became encapsulated.

Case 3

A 50-year-old female, housewife, educated upto 8^th standard, with no past family or history of psychiatric illness or medical co-morbidity, self-reported in November 2021 with uncomfortable sensation of insects crawling over her body since past 3 months.

She was apparently well till September 2021 when she started having crawling sensations of some insects over her abdominal region which over next few days became generalised. Initially, she suspected this to be due to left-over pathogens from Tuberculosis which she had recovered from 4 years back. She was noted by family members to be picking her skin throughout the day. After around two months, she started hearing clicking sounds of these pathogens and started believing that these pathogens are inside her body and that the illness has recurred. She consulted a general practitioner initially, who advised her anti-helminthic drugs and later Tab Levocetirizine, permethrin ointment and benzyl benzoate cream but without any relief. She also bought Tab Ivermectin tablet from a nearby medical store but it was of no avail. She was then referred by the treating physician for psychiatry consultation.

In OPD, she was investigated and was then referred for a dermatologic consultation in view of excoriations over her body. Her laboratory evaluation and radiological examination were normal. During dermatological evaluation, there was no evidence of any cutaneous disorder. Based on clinical evaluation and MSE findings, she was diagnosed as a case of delusional parasitosis. She was treated with Tab Olanzapine 10 mg/day and was also benefitted with supportive psychotherapy and CBT. She responded well and over a period of 2–3 months and achieved remission.

Case 4

A 69-years-old male, educated upto 10^th, with no past or family history of psychiatric illness or medical co-morbidities was referred from ECHS polyclinic in March 2022 where he had reported with the complaints of being infested by insects which bite him all over the body since past 7 years.

Onset of symptoms was in 2015 while working as a security guard in telephone exchange where he slept in a dirty room on the floor. One day, while sleeping, he had itching over his face and thought he was bitten by an insect. Over the next few days, he started having itching regularly, sometimes over his chest and thighs and sometimes, all over his body. At times, he used to wake up from sleep and jerked off his clothes but could not find anything. He suspected that some insects might have entered inside his body while he was sleeping via his ears and nose. He took medicines from a local medical store and had some relief. After being operated for cataract in his left eye in 2016, he saw some discharge and debris coming out from the eye and thought of this as remnants of dead insects. He then concluded that he is infested from the insects and that these insects enter inside his body when he sleeps. He would sleep with his windows closed, sprayed insecticide and clean his bed sheet every time he went to sleep in order to prevent further spread.

He visited local doctors and physicians multiple times tried ayurvedic medicines and homeopathic medicines but of no avail. He then visited ECHS polyclinic, from where he was referred to psychiatry OPD. All relevant investigations including neuroimaging were normal. NCCT head was also normal.

He was diagnosed as a case of delusional parasitosis in view of above symptoms. He was started on Tab Olanzapine 5 mg which was increased gradually to 20 mg over a period of 2 months along with eclectic psychotherapy. Dermatology consultation was also taken for dermatitis due to itching. There was a gradual reduction in symptoms by 50–60%. Over a period of another 2-3 months, his delusion of insect manifestation became encapsulated with improvement in symptoms being attributed to reduction in number of insects due to medicine.

DISCUSSION

DP is characterised by fixed belief of being infested by a parasite when one is not. Patients persist with this belief despite negative clinical examination and reassurance. DP is a rare presentation in psychiatry practice. It is seen more commonly in women and onset is generally in 5^th to 6^th decade of life.

Epidemiological data, as mentioned earlier, are limited and the prevalence of this illness is often underestimated.[12] Over a period of one year, a total of 20 patients were diagnosed with delusional disorder in our centre. Of these, four patients were diagnosed with delusional parasitosis (20%). Three of these cases were females. These patients were treated with Olanzapine. Further they were given add on eclectic psychotherapy in the form of reassurance, supportive psychotherapy, psychoeducation and cognitive behaviour therapy as appropriate. The evidence for efficacy of olanzapine was obtained from case reports, case series, reviews and one systematic review.[13-15] This case series adds to the existing literature on Olanzapine as an effective treatment strategy for patients with DP.[13]

The treatment of delusional parasitosis is difficult and is often time-consuming. We were able to achieve fair remission in these patients. This case series brings to the fore certain relevant points. Firstly, timely treatment in patients with DP leads to gratifying results. Secondly, patients respond to a mix of antipsychotics and psychotherapy. One patient in our setup showed some EPSEs for which Tab Trihexyphenidyl 2 mg/day was added. The response was slow to occur and even in patients with an improvement in symptoms; sometimes encapsulation of delusion was observed. Hence, there is a necessity to keep the patients under regular follow-up. Also, as most patients consult the dermatologist first,[16] an early referral to psychiatrist will help in not only preventing development of any associated co-morbidity, but also dermatological sequalae.

Declaration of patient consent

The authors declare that they have obtained consent from patients. Patients have given their consent for their images and other clinical information to be reported in the journal. Patients understand that their names will not be published and due efforts will be made to conceal their identity but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.