Management of Delusional Parasitosis in a 70-Year-Old Male
This patient most likely has delusional parasitosis (also known as Ekbom syndrome or delusional infestation), a psychiatric condition where the patient has a fixed false belief of being infested with parasites despite no objective evidence of infestation.
Initial Clinical Assessment
Rule Out Actual Parasitic Infestation First
- Perform a thorough skin examination of the posterior neck looking for any actual tick attachment, embedded tick parts, or signs of tick-borne disease such as erythema migrans, petechial rash, or eschar 1
- Examine for visible parasites or evidence of infestation including excoriations, burrows, or actual organisms on the skin surface 2
- If a tick is actually present and attached, remove it promptly with fine-tip forceps and monitor for development of fever, headache, myalgias, or rash over the next 2-3 weeks 1, 3
Key Red Flags That Would Indicate True Tick-Borne Disease
- Fever, severe headache, myalgias, and confusion developing within 3-14 days of potential tick exposure would necessitate immediate empirical doxycycline 100 mg twice daily 3, 4
- Leukopenia, thrombocytopenia, or elevated transaminases in the setting of recent outdoor activity would strongly suggest ehrlichiosis or anaplasmosis and require immediate treatment 1, 4
- Petechial rash, particularly on extremities, combined with systemic symptoms indicates possible Rocky Mountain spotted fever 1, 3
When No Parasite Is Found
Diagnostic Criteria for Delusional Parasitosis
- Fixed false belief of parasitic infestation persisting despite negative examination and reassurance
- No fever, systemic symptoms, or laboratory abnormalities that would suggest actual tick-borne rickettsial disease 1
- Patient may present with self-inflicted excoriations from attempts to remove the perceived parasite 2
- The "matchbox sign" (bringing in specimens of skin debris, lint, or scabs claiming they are parasites) is pathognomonic
Management Approach
Do not prescribe ivermectin or other antiparasitic medications as they are ineffective for delusional parasitosis and ivermectin has significant neuropsychiatric side effects including confusion, lethargy, and mental status changes 5
Establish therapeutic alliance without directly confronting the delusion:
- Acknowledge the patient's distress and suffering as real
- Avoid arguing about whether parasites exist
- Frame treatment as "helping with the sensations" rather than treating delusions
Refer to psychiatry or dermatology for definitive management, as primary care physicians refer 37.5% of dermatological presentations, often to establish diagnosis of lesions of unknown origin 6, 7
Pharmacological Treatment (Typically Initiated by Psychiatry)
- Antipsychotic medications are the primary treatment for delusional parasitosis
- Second-generation antipsychotics (risperidone, olanzapine, aripiprazole) are preferred over first-generation agents
- Treatment duration typically requires several months to years
Critical Pitfalls to Avoid
- Never delay doxycycline if actual tick-borne disease is suspected while waiting for psychiatric evaluation, as mortality from untreated rickettsial disease is 3-5% 4
- Do not prescribe prophylactic antibiotics after a tick bite in the absence of symptoms, as this is not recommended for rickettsial diseases 3
- Do not perform unnecessary skin biopsies solely to reassure the patient, as negative results rarely change the fixed belief 6
- Avoid prescribing ivermectin empirically as it can cause serious neurological adverse effects and will not address the underlying psychiatric condition 5