Practice Practice Pointer

How to approach delusional infestation

BMJ 2015; 350 doi: https://doi.org/10.1136/bmj.h1328 (Published 01 April 2015) Cite this as: BMJ 2015;350:h1328
  1. Peter Lepping, consultant psychiatrist; honorary professor1,
  2. Markus Huber, consultant psychiatrist2,
  3. Roland W Freudenmann, consultant psychiatrist; associate professor3
  1. 1Betsi Cadwaladr University Health Board, North Wales, Wrexham, UK; Centre for Mental Health and Society, Bangor University, Bangor, UK; Mysore Medical College and Research Institute, Mysore, India
  2. 2Department of Psychiatry, General Hospital Bruneck, South Tyrol, Italy
  3. 3Department of Psychiatry and Psychotherapy III, University of Ulm, Ulm, Germany
  1. Correspondence to: P Lepping peter.lepping{at}wales.nhs.uk

The bottom line

  • Consider delusional infestation in patients who present with a fixed belief that they are infested with living or non-living organisms in the absence of medical evidence for this

  • Always exclude real infestations first, with examination, review by a dermatologist or infectious disease specialist, and appropriate tests

  • Acknowledge the patient’s distress without reinforcing false beliefs

  • Most patients require antipsychotic treatment (amisulpride, olanzapine, or risperidone), which may be offered as a means to alleviate symptoms

  • Management ideally requires a multidisciplinary approach, but, as patients rarely agree to full psychiatric assessment, physicians who have engaged patients in a trusting relationship should offer medication, if possible with psychiatric advice

Delusional infestation (previously also known as delusional parasitosis or Ekbom’s syndrome) is a rare disorder, but it commonly poses disproportionate practical problems to healthcare systems.1 It is characterised by a patient’s fixed belief that his or her skin, body, or immediate environment is infested by small, living (or less often inanimate) pathogens despite the lack of any medical evidence for this.1 Delusional infestation is neither a single disease nor a single diagnostic entity. The classic form, primary delusional infestation, develops without any known cause or underling illness and meets criteria for a persistent delusional disorder (ICD-10 (international classification of diseases, 10th revision)) or delusional disorder somatic type (DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, fifth edition)). Approximately 60% of patients, however, have secondary forms of delusional infestation2 that occur in the context of substance misuse (such as cocaine, amphetamines, cannabis), dopaminergic medications, antibiotics, or during physical or psychiatric illnesses (such as delirium, dementia, depression, schizophrenia, stroke, and other medical conditions that affect the brain or cause pruritus).1 2

The neurobiology of delusional infestation is not fully understood. Studies point to dysfunction or structural brain damage in the frontal cortex, …

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