CONTINUING MEDICAL EDUCATION A Review of Delusions of Parasitosis, Part 1: Presentation and Diagnosis Rachel Bak, MD; Phani Tumu, MD; Christina Hui, MD; David Kay, BA; Julie Burnett; David Peng, MD GOAL To understand delusions of parasitosis (DOP) to better manage patients with the condition OBJECTIVES Upon completion of this activity, dermatologists and general practitioners should be able to: 1. Identify criteria for diagnosing DOP. 2. Describe features associated with DOP. 3. Discuss possible causes of DOP. CME Test on page 136. This article has been peer reviewed and approved Einstein College of Medicine is accredited by by Michael Fisher, MD, Professor of Medicine, the ACCME to provide continuing medical edu- Albert Einstein College of Medicine. Review date: cation for physicians. July 2008. Albert Einstein College of Medicine designates This activity has been planned and imple- this educational activity for a maximum of 1 AMA mented in accordance with the Essential Areas PRA Category 1 CreditTM. Physicians should only and Policies of the Accreditation Council for claim credit commensurate with the extent of their Continuing Medical Education through the participation in the activity. joint sponsorship of Albert Einstein College of This activity has been planned and produced in Medicine and Quadrant HealthCom, Inc. Albert accordance with ACCME Essentials. Drs. Bak, Tumu, Hui, and Peng; Mr. Kay; and Ms. Burnett report no conflict of interest. The authors report no discussion of off-label use. Dr. Fisher reports no conflict of interest. Delusions of parasitosis (DOP), a psychiatric and treatment with psychotropic medications. We disorder in which patients erroneously insist discuss the classification, epidemiology, clinical that they are infested with parasites, remains a presentation, etiology, associated features, and fascinating entity with elusive origins. Typically, differential diagnosis of this disorder. The authors these patients are resistant to psychiatric referral reviewed case reports and clinical trials and tabu- lated the epidemiologic data, which show DOP is Accepted for publication May 16, 2007. more common than previously thought. Dr. Bak is a family practice resident, Northridge Hospital Medical Cutis. 2008;82:123-130. Center, California. Dr. Tumu is a psychiatry resident, Los Angeles County–University of Southern California Medical Center. Dr. Hui is a psychiatry resident, Department of Psychiatry, Harbor–University of California at Los Angeles Medical Center, Torrance. Mr. Kay is a elusions of parasitosis (DOP) is a disorder char- graduate of Queens College, New York. Ms. Burnett is a medical acterized by patients who erroneously insist student and Dr. Peng is Assistant Professor, Department of that they are infested with parasites. The dis- Dermatology, both at Keck School of Medicine, University of D Southern California, Los Angeles. order is encountered by physicians in a wide variety Correspondence: Rachel Bak, MD, 12733A Chandler Blvd, Valley of specialties, including dermatology, family practice, Village, CA 91607 ([email protected]). infectious disease, internal medicine, and psychiatry, VOLUME 82, AUGUST 2008 123 Delusions of Parasitosis yet its etiology and impetus for affecting some patients more referrals than others based on their history of and not others remain unclear. treating DOP; and while an inpatient population is most easily studied, most patients with DOP are Classification seen on an outpatient basis. Furthermore, physicians Delusions of parasitosis has been referred to by many depend on the unreliable method of self-reporting to names over the years, including parasitophobia1 identify this disease. Because infestation is socially and acarophobia2; delusions of dermatozoiasis, der- unacceptable, patients may be embarrassed to report matophobia, entomophobia3; parasitophobic neu- their symptoms, fearing judgment on their socioeco- rodermatitis; Ekbom syndrome4; and most recently, nomic status, hygiene, and mental health. Delusions Morgellons disease.5 According to the Diagnostic and of parasitosis may be more prevalent in areas where Statistical Manual of Mental Disorders (Fourth Edition), infestation is more commonplace and, consequently, DOP is considered a form of psychosis.6 Specifically, it considered a more acceptable diagnosis. Srinivasan is classified as a delusional disorder of a somatic sub- et al19 discuss this phenomenon in India. type. It is distinguished from paranoia, a disorder in The female to male ratio has ranged from 2 to 1 which patients know their fear is irrational.7 Instead, in 2 UK surveys,10,22 to 2.2 to 1 in a tabulated series,3 DOP is a fixed false belief of infestation. This belief to 2.8 to 1 in a single study of 57 cases,23 to 4 to 1 in is nonbizarre; it is conceivable that a person could, in a retrospective analysis of 20 cases.14 Furthermore, theory, have a parasitic infection. female predominance is reported by Lyell10 to be To diagnose DOP, patients must meet the fol- stronger at an older age. The mean age of onset lowing criteria: (1) a delusion of at least 1 month’s ranges from 50 to 69 years. A bimodal distribution duration; (2) no prior diagnosis of schizophrenia8; with some patients presenting in their 20s or 30s (3) psychosocial functioning is not impaired other also has been described.8 Folie à deux, a delusion than directly by the delusion; (4) if a mood disorder shared by another person, was estimated to occur coexists, the mood disturbance is shorter in duration in approximately 8% to 10% of patients (in stud- than the delusion; and (5) the delusion is not caused ies with .100 patients).10,24 The authors reviewed by substance use or another medical condition.6 demographic data from 61 articles published on Delusions of parasitosis also can be classified this topic.3,10,15-21,25-76 Delusions of parasitosis was as monosymptomatic hypochondriacal psychosis, reported in 150 females and 82 males (a 1.8:1 ratio a term used to emphasize that DOP, among other of females to males). The mean age of onset was disorders of this type, is encapsulated. Patients with 57.9 years, with 59.2 years for females and DOP often are perfectly appropriate in behavior 55.5 years for males. Of cases in which data were and logic in all other aspects of life.2 However, they available, 11% (16/150) reported evidence of folie have this single, firm, persistent delusion of infesta- à deux and 50% (63/128) presented with proof tion. Patients with other psychotic disorders, such of infestation. Of 95 cases reported, 34% (32/95) as schizophrenia, usually have other psychological presented to dermatologists and 29% (28/95) pre- signs, such as blunted affect and auditory halluci- sented to psychiatrists (Figure). nations, in addition to their delusions.9 Patients can present with parasitic delusions caused by an Clinical Presentation underlying organic disorder, but they are not true The classic patient with DOP is a middle-aged cases of DOP. woman frustrated by unsuccessful attempts to dis- cover the cause of her ailment that has been affecting Epidemiology her for months or years. She has probably presented While the prevalence of this disorder is unknown, it to many physicians in different specialties. She has has been described in the literature as rare.10 How- the unshakable belief that she is infested. She may ever, many researchers have speculated that the prev- believe she is infested by a specific insect and even alence is indeed greater than initially suspected.8,11-13 describes the color or shape of the bugs. Despite the A retrospective study at the University of Cologne, lack of clinical evidence, she may claim to actually see Germany, reported a prevalence of 67 cases per the bugs crawling on her77 and feel the sensation of 1000 psychiatric admissions.14 Various authors have biting or burrowing under the skin (formication). She reported incidences in their clinics averaging from will commonly bring in proof of infestation, such as 0.6 to 20 cases per year (Table).15-21 visible particles on clear tape or in little plastic bags, The overall prevalence is difficult to assess which is called the matchbox sign because patients, as because the disorder may be referred to by differ- described in older literature, brought their evidence ent names; physicians of some specialties will see in matchboxes. A more recent report appropriately more cases than others; certain physicians will get suggested modernizing the term to the Ziploc® sign.77 124 CUTIS® Delusions of Parasitosis Reported Incidences of Delusions of Parasitosis No. of Cases Specialty Location Per Year, mean Reference Entomology Los Angeles Department 20 Schrut and Waldron15 of Health, California Psychiatry Outpatient Clinic, 20 Ungvari and Vladar16 Budapest, Hungary Psychiatry Outpatient Clinic, 6.1 Bhatia et al17 Delhi, India Psychiatry/ Outpatient Clinic, 5.8 Tandon18 Dermatology Allahabad, India Psychiatry Outpatient Clinic, 4.8 Srinivasan et al19 Madras, India Psychiatry Private Practice, 2.7 Sheppard et al20 Dublin, Ireland Dermatology Division of Dermatology, 0.6 Aw et al21 National University Hospital, Singapore Upon examination, the particles are nothing more with DOP because of its antipruritic effects mediated than skin scrapings, lint, or other nonparasitic mate- through opiate agonism. Pimozide has activity similar rials. Frequently, the patient presents with neurotic to morphine and fentanyl citrate. A controlled trial excoriations or inflammation secondary to scratching clinically linked