History: A mite disturbing
Mrs. K, age 60, a social worker, saw mites on her arm 3 months ago while going through a client’s old belongings. Since then, she reports, she and her house have become infested with mites.
Despite using copious amounts of lotions, baths, sprays, and prescription creams, she sees increasingly visible “creatures” all over her body and in her stool. Three doctors found no physical evidence of infestation, however, and she became indignant after one told her the problem is “in her head.”
A veterinarian treated Mrs. K’s cat for mites. Days later, Mrs. K suspected that the cat had become reinfested at home and returned it to the veterinarian. He assured her the cat was fine, but she was afraid to bring it home. The cat has remained at the veterinarian’s office—to the doctor’s displeasure—for weeks.
Two weeks after Mrs. K first spotted the mites, her husband, age 82, started believing he is infested. Mr. K, who is retired, has battled depression and drinks about a half-gallon of liquor daily.
After 2 months, Mrs. K quit her job for fear she would infest her co-workers, then locked herself and her husband in their house and allowed no visitors. Day and night for nearly 3 weeks, Mrs. K repeatedly vacuumed the house, shampooed the carpets, and sprayed the walls and furniture with a homemade insecticide. She taped the windows closed to keep bugs out and covered all furniture and surface areas with plastic. A toxic stench of insecticide and shampoo permeated every room.
A neighbor told Mrs. K’s son that his parents were locked inside their house. He came over and knocked on their door, but was refused entry. He eventually got Mrs. K out by threatening to call the police, then brought her to the emergency room.
At presentation, Mrs. K’s right leg has scratches and scabs caused by frequent scratching at mites she saw there. Her hands are reddened and dry, suggesting chemical dermatitis caused by cleaning and repeated insecticide use. Ritual cleaning and spraying has kept her from eating or sleeping; she has lost 12 lbs over 3 weeks and looks pale and tired.
A recovered alcoholic, Mrs. K has been sober for 12 years. She has no other psychiatric, medical, or dermatologic history, and has few social contacts beyond her family and workplace acquaintances.
Blood chemistry, CBC, and urine drug test results are normal. Head MRI reveal no neurologic abnormalities. Her Mini-Mental State Examination (MMSE) score (29/30) indicates no cognitive impairment.
Mrs. K is hospitalized to separate her from her allegedly bug-infested household and husband. At intake, she is panicked over leaving her husband alone and distressed that no one except she and her husband can see the bugs infesting their house and covering her skin. She asks doctors to test a small piece of toilet paper, which she says contains a sample of the bugs. She also fears that she infested her son by letting him into her house.
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The authors’ observations
Mrs. K’s presentation and clinical course suggest delusional parasitosis, a fixed false belief of a parasitic infestation that can cause significant social and occupational dysfunction and medical problems. One patient calls this disorder “bugaphobia.”
The disorder may start as a self-perceived invisible infestation and evolve into visual hallucinations of bugs. Patients usually believe their skin is infested; some believe their internal organs, gums, or skin and internal organs are infested.1,2
Table 1
Medical conditions that may precede delusional parasitosis
| Anemia (severe) |
| Cancer |
| CNS infections |
| Head injury |
| Hepatitis |
| Hypertension |
| Hypovitaminosis of vitamin B12, folate, or thiamine |
| Multiple sclerosis |
| Pulmonary disease |
| Renal disease |
| Rheumatologic disease |
| Sight or hearing loss |
| Source: Reference 6 |
Some patients misinterpret scabs, abrasions, or skin irritation secondary to pesticide use as signs of infestation. Delusional parasitosis can also develop after a real, one-time infestation, as may have happened with Mrs. K.
Convinced they are infested, patients consult multiple providers—including dermatologists, gastroenterologists, and ophthalmologists—in search of the “right” treatment. They undergo numerous tests or procedures and repeatedly apply prescription creams and lotions, leading to chemical dermatitis. Patients often try to prove they are infested by bringing skin, dirt, or toilet tissue samples to doctors—this is called the “matchbox sign” because patients generally bring these samples in small boxes.4 They also may repeatedly ask veterinarians to disinfest their pets.