Letter to the Editor

Dear Editor,

Delusional parasitosis (DP) is a psychiatric condition in which patients believe they are parasitized by bugs, worms, or small living organisms.1 Patients usually complain of itching, which they ascribe to the presence of bugs in or under the skin. Here, we report a rare case of successful DP treatment in a patient with early-onset Alzheimer’s disease (AD) using cognitive behavioral therapy (CBT) and medication. The patient was 58 years old, had 12 years of formal education, and was right-handed. One year ago, she was diagnosed with early-onset AD based on the results of detailed neuropsychological and amyloid positron emission tomography tests and was under follow-up while using medication (memantine 20 mg/day). Her Mini-Mental State Examination, Clinical Dementia Rating, Global Deterioration, and Geriatric Depression Scale scores were 19, 1, 5, and 4, respectively. The patient was slightly indifferent to her disease but had no prominent behavioral and psychological symptoms of dementia.

The patient complained of an intense itching sensation on the anterior aspect of her lower extremities that had been present for approximately three months. She described the sensation as “bugs crawling” and repeated the act of making numerous cuts on her legs with a utility knife to kill the bugs (Fig. 1A). Several dermatologists confirmed that the patient has no skin disease that can cause itching. There were no abnormal findings on complete physical examination or extensive laboratory evaluation. We speculated that the patient may have developed secondary DP associated with early-onset AD. Since she was suffering from the feeling of “bugs crawling” in her sleep and agitation was very severe, 12.5 mg quetiapine (every night at bedtime) and 5 mg escitalopram (once a day) were initiated. Four weeks after starting these medications, the patient’s sleep slightly improved; however, the symptoms of DP did not improve. The doses of quetiapine and escitalopram were titrated to 25 and 10 mg, respectively, and the patient was referred to a local public health center to participate in CBT. The CBT provided by the Gyeonggi Province Metropolitan Center for Dementia included cognitive training, art, and music therapy, and the patient was treated twice a week for 3 hours each time. After three months, the symptoms of DP improved markedly. She no longer had the feeling of “bugs crawling” and had ceased cutting her legs with a utility knife (Fig. 1B). Despite continued deterioration in cognitive function due to AD, the patient no longer showed DP symptoms after a year of follow-up.