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Delusions of parasitosis is a rare condition that presents as a false but fixed belief in infection by parasites, bacteria, mites, fungi, worms, or other organisms. Most delusions of parasitosis patients report dermatological symptoms. They believe they have a skin manifestation of a parasitic infection. However, the disorder is psychiatric and requires a cautious approach.

Primary care doctors are at the frontline in most cases. The best way to start treatment is to accept the patient’s convictions at the beginning. That’s how clinicians can initially win their trust and create a chance to bridge the gap between those convictions and understanding the actual situation.

That’s essential because patients with delusions of parasitosis are easily agitated when doctors disregard their symptoms as false, and they tend to reject the psychiatric referral.

For further information on this topic, you may be interested to learn more about the HealthCert Professional Diploma program in General Dermatology.

Overview

Delusions of parasitosis are rarely a primary disorder, and it is more commonly a symptom of a secondary psychiatric condition or medical illness, such as:

• Schizophrenia
• Hyperthyroidism
• Vitamin B12 deficiency
• Folate deficiency
• Drug abuse
• Alcohol withdrawal
• HIV infection
• Leprosy
• Syphilis
• Neuropathy
• Diabetes
• Dementia
• Encephalitis
• Stroke
• Medications side effects

The role of primary care doctors is not to diagnose and treat all these potential causes but to determine if the reported manifestations are reality or delusions. Adequate training in general dermatology and the ability to recognise the symptoms is essential here.

The symptoms

Patients suffering from delusions of parasitosis will often report symptoms such as:

• Rashes
• Pruritus
• Formication
• Stinging

They will often insist on these symptoms even when there are no physical findings to confirm a potential cause and after a topical or medications therapy.

On the other hand, the attempts by patients to physically remove the “parasites” may be visible. These can include:

• Punctures
• Scars
• Excoriations
• Scratches
• Irritant dermatitis

Diagnosis

The first step in diagnosing delusions of parasitosis is ruling out the infection (parasitic or other). The physician should thoroughly evaluate the patient’s medical history, travel history, contacts with other people with similar symptoms, and potential exposure to pet-borne infections.

A complete blood count with a focus on increased eosinophils is helpful.

Doctors should also look for potential secondary causes, such as:

• Thyroid disorders,
• Neurological disorders,
• Vitamin deficiencies,
• Various infections, and
• Leprosy

Referral to a dermatology specialist is sometimes necessary too. That helps build a quality relationship with the patient as it shows consideration of their distress and frustration.

Treatment

Dismissing patients’ complaints as false is almost always counterproductive. It only increases frustration and distrust, minimising the chances the patient will follow the proposed treatment plan.

Acknowledging their symptoms and the effect of the issue on their everyday life is the best way to go. That means a neutral but honest approach. Not dismissing the possibility of a previous infection but clearly stating that there are no signs of a currently present one.

Antipsychotics are the usual first-choice treatment option for delusions of parasitosis. Most patients refuse the idea of a direct connection between their symptoms and a psychiatric disorder. So, it is a doctor’s job to explain how the medications can help without linking them or the issue with schizophrenia or another “unpopular” condition.

– Dr Rosmy De Barros

Read another article like this one: Cutaneous symptoms of sexually transmitted infections

References:

• Mumcuoglu KY, Leibovici V, Reuveni I, Bonne O. Delusional Parasitosis: Diagnosis and Treatment. Isr Med Assoc J. 2018;20(7):456-460.
• Reich A, Kwiatkowska D, Pacan P. Delusions of Parasitosis: An Update. Dermatol Ther (Heidelb). 2019 Dec;9(4):631-638. doi: 10.1007/s13555-019-00324-3. Epub 2019 Sep 13. PMID: 31520344; PMCID: PMC6828902.
• Ansari MN, Bragg BN. Delusions Of Parasitosis. In: StatPearls. Treasure Island (FL): StatPearls Publishing; May 23, 2022.
• Linder D. Delusional Infestation – Importance of Early Treatment. Acta Derm Venereol. 2020;100(16):adv00262. doi:10.2340/00015555-3626
• Gold A, Roit Z, Llovera I. Pitfalls and Pearls in Delusional Parasitosis. Clin Pract Cases Emerg Med. 2019 Oct 14;3(4):387-389. doi: 10.5811/cpcem.2019.8.44619. PMID: 31763595; PMCID: PMC6861047.