Should a 70-year-old man with neurotic excoriations due to delusional parasitosis be referred to dermatology?

Should You Refer to Dermatology for Neurotic Excoriations in Delusional Parasitosis?

No, you should not refer to dermatology—dermatologists should manage delusional parasitosis directly and initiate antipsychotic treatment themselves, ideally after consulting with a liaison psychiatrist. 1

Primary Management by Dermatology

Dermatologists play the primary role in both diagnosis and treatment of delusional parasitosis, including prescribing antipsychotic medications. 1 This approach is critical because:

• Patients with delusional parasitosis typically refuse psychiatric referral, as they are convinced they have a dermatological problem rather than a psychiatric condition 2, 3
• These patients present to dermatology clinics specifically because they reject the notion of a psychiatric basis for their symptoms 3
• Immediate confrontation or psychiatric referral is counterproductive and often results in treatment refusal 3

Establishing the Therapeutic Relationship

Maintain continuity of care with the same dermatologist to build the trust essential for medication adherence. 1 The treatment approach should include:

• An initially supportive, nonconfrontational, empathic approach without immediate confrontation about self-induced lesions 3
• Frequent visits and symptomatic topical treatments in the beginning to establish rapport 3
• Frame antipsychotic medication as treatment for physical sensations (crawling, biting, pruritus) rather than for a psychiatric condition to increase acceptance 1

Diagnostic Confirmation Before Treatment

Rule out secondary causes before diagnosing primary delusional parasitosis:

• Perform skin examination and laboratory testing to exclude actual parasitic infestation 1
• Screen for substance abuse (particularly stimulants), medications, neurological diseases (dementia, stroke, Parkinson's), and medical conditions (thyroid disease, vitamin deficiencies) that can produce secondary delusional symptoms 1, 4
• Identify comorbid psychiatric disorders including depression, anxiety, and obsessive-compulsive disorder 1
• Assess for shared psychotic disorder, as up to 15% of cases involve family members with similar symptoms 1, 4

Pharmacological Treatment Protocol

Implement antipsychotic treatment for 4-6 weeks before determining efficacy, as antipsychotic effects typically become apparent after 1-2 weeks. 1 Specific recommendations include:

• Consider atypical antipsychotics (risperidone) as first-line treatment, particularly in elderly patients or those with cardiac risk factors 1, 2
• Pimozide remains an effective option at dosages of 1-10 mg/day, using the lowest effective dose for the shortest duration 2, 5
• Monitor for extrapyramidal symptoms (stiffness, akathisia) and treat with benztropine 1-2 mg up to 4 times daily or diphenhydramine 25 mg 3 times daily as needed 2
• For pimozide doses <10 mg/day in non-elderly patients without cardiac history, routine ECG monitoring may not be necessary 2

Collaborative Care Model

Close collaboration among dermatologists, psychiatrists, and parasitologists is essential, with dermatologists maintaining the primary prescribing role after consulting a liaison psychiatrist. 1, 5 This dermatology-psychiatry liaison approach allows for:

• Establishing a viable differential diagnosis 5
• Selecting appropriate therapy while maintaining patient engagement 5
• Including families in the treatment plan with emotional support and practical advice 1

Critical Pitfalls to Avoid

• Don't immediately refer to psychiatry—this typically results in treatment refusal and loss to follow-up 2, 3
• Don't miss secondary causes (substance abuse, medications, neurological disease, genuine parasitic infestation) before diagnosing primary delusional parasitosis 1, 4
• Don't use excessive antipsychotic doses, as this increases side effects without improving efficacy 1
• Don't confront patients immediately about the psychiatric nature of their condition—build trust first through symptomatic treatment 3

Recognizing the Pathognomonic Sign

The "creature collection sign" (also called matchbox sign, specimen sign, or pillbox sign) is pathognomonic for delusional infestation, where patients present containers with collected "parasites" to prove their infestation 4. Recognition of this sign confirms the diagnosis and should prompt dermatologist-initiated treatment rather than referral.