“Doctor, I KNOW I have worms crawling out of my skin, I have one in a plastic bag here and I also have some (a lot) of pictures on my phone to look at as well." Delusional infestation also known as delusional parasitosis or Ekbon’s syndrome and the related Morgellon’s syndrome (replace parasites with fibers) are not extremely common conditions, but are prevalent enough that many primary care providers have heard phrases such as this. Patients who suffer this condition are profoundly convinced that they have one or more types of living creatures crawling in, around or out of their skin or other dermal structures despite the lack of any objective evidence of such a problem. Scratching or digging for the parasites often leads to self-mutilation.

Key DSM 5 diagnostic criteria are greater than one month of symptoms, generally functional outside of the parasitic delusion and no other medical or substance use problems that could wholly explain the condition. The mean age of onset (typically gradual in nature) is the late 50s and there is a 3:1 female to male ratio. Affective disorders, anxiety and substance abuse are common in the background. About a quarter of the time, a significant other will also be drawn into the delusion (Folie a deux).

Work up does include a search for underlying conditions that may exacerbate the problem. These include the following: scabies or lice, allergic or contact dermatosis, medications such as dopamine agonists, opioids, topiramate, amphetamines, corticosteroids, fluoroquinolones, benzodiazepines and cocaine, pruritis inducing conditions such as renal and liver failure and hyperthyroidism and other contributing diseases such as dementia, hypothyroidism, B12 deficiency, diabetes, post herpetic neuralgia and anemia. Searching for and correcting these conditions not only may help the problem but also helps to build trust. Useful tests include CBC for eosinophilia, CMP, TSH, CRP and urine toxicology screen. A single punch biopsy of a patient-selected lesion may also be helpful but repeated biopsies are counterproductive.

Treatment includes include pre-visit preparation of strategy to control the conversation; establishing a rapport by acknowledging the patient’s distress and severity of experience with a positive attitude; performing a work up as noted; initiating antipsychotic therapy focusing on symptom relief and maintaining therapy for 3-4 months before tapering off at 6 months (75% cure rate expected). Low dose risperidone (0.5 to 2 mg daily) or olanzapine (2.5 to 12 mg daily) are the commonly used medications and can be tapered up to achieve symptom relief. Psychiatric consultation is an important adjunct to therapy, but patients commonly reject a psychiatric basis for their disease and initially refuse referral. Starting drug treatment may improve willingness to comply with psychiatric referral. Referrals to dermatology or infectious diseases can help exclude organic disease but are not a guaranteed bridge to effective treatment.

Delusional infestation is a debilitating condition which frequently uses a large amount of medical resources due to doctor shopping, ER visits and uncoordinated evaluations. An organized approach that can be successfully initiated in the primary care office may provide the affected patient a tremendous amount of relief.

References:

Campbell, EH et. al. “Diagnosis and management of delusional parasitosis” J Am Acad Dermatology, 80:1428-34, 201

Gold, A, et. al. “Pitfalls and pearls in delusional parasitosis” Clin Pract Cases Emerg Med 3: 387-389, 2019

Moriarty, N, et. al. “Current understanding and approach to delusional infestation” Am J of Med, 132: 1401-1409, 2019