Infested with worms, but are they really there?

The authors’ observations

Delusional parasitosis (DP), also known as delusional infestation or Ekbom Syndrome, is a condition characterized by the fixed, false belief of an infestation without any objective evidence. This condition was previously defined in DSM-IV, but was removed from DSM-5-TR. In DSM-5-TR, DP is most closely associated with delusional disorder—somatic type (Table 1¹). It describes a patient with ≥1 month of delusions who does not meet the criteria for schizophrenia with a central theme of delusions involving bodily functions or sensations such as infestation of insects or internal parasites.¹

DP is rare, affecting approximately 1.9 per 100,000 people. There has not been consistent data supporting differences in prevalence between sexes, but there is evidence for increasing incidence with age, with a mean age of diagnosis of 61.4.^2,3 DP can be divided into 2 types based on the history and etiology of the symptoms: primary DP and secondary DP. Primary DP occurs when there is a failure to identify an organic cause for the occurrence of the symptoms. Therefore, primary DP requires an extensive investigation by a multidisciplinary team that commonly includes medical specialists for a nonpsychiatric workup. Secondary DP occurs when the patient has delusional symptoms associated with a primary diagnosis of schizophrenia, depression, stroke, diabetes, vitamin B12 deficiency, or substance use.⁴

Though Mr. H initially presented to the ED, patients with DP commonly present to a primary care physician or dermatologist with the complaint of itching or feelings of insects, worms, or unclear organisms inside them. Patients with DP may often develop poor working relationships with physicians while obtaining multiple negative results. They may seek opinions from multiple specialists; however, patients typically do not consider psychiatrists as a source of help. When patients seek psychiatric care, often after a recommendation from a primary care physician or dermatologist, mental health clinicians should listen to and evaluate the patient holistically, continuing to rule out other possible etiologies.

TREATMENT Finding the right antipsychotic

In the psychiatric unit, Mr. H says he believes worms are exiting his ears, mouth, toenail, and self-inflicted scratch wounds. He believes he has been dealing with the parasites for >1 year and they are slowly draining his energy. Mr. H insists he contracted the “infection” from his home carpet, which was wet due to a flood in his house, and after he had fallen asleep following drug use. He also believes he acquired the parasites while walking barefoot along the beach and collecting rocks, and that there are multiple species living inside him, all intelligent enough to hide, making it difficult to prove their existence. He notes they vary in size, and some have red eyes.

During admission, Mr. H voices his frustration that clinicians had not found the worms he has been seeing. He continuously requests to review imaging performed during his visit and wants a multidisciplinary team to evaluate his case. He demands to test a cup with spit-up “samples,” believing the parasites would be visible under a microscope. Throughout his admission, Mr. H continues to take buprenorphine/naloxone and does not experience withdrawal symptoms. The treatment team titrates his quetiapine to 400 mg/d. Due to the lack of improvement, the team initiates olanzapine 5 mg/d at bedtime. However, Mr. H reports significant tinnitus and requests a medication change. He is started on haloperidol 5 mg twice daily.

Continue to: Mr. H begins to see improvements...