Persistent Inflammatory Response Following Arthropod Bite with Dermatographic History

Case at a Glance

A 31-year-old Caucasian female presents with a one-week history of persistent erythematous, pruritic skin lesion following an arthropod bite, unresponsive to topical corticosteroids and antihistamines.

Patient's Story

The patient reports being bitten by an unknown arthropod one week prior to presentation while in Ontario, Canada. The bite occurred in the infraclavicular region and was immediately noticeable due to its prominent location. She denies observing a tick attachment and states the bite area has been consistently itchy, warm, and erythematous since the initial incident. The patient has a medical history significant for dermatographia, which was previously active but has been largely quiescent recently.

Initial Assessment

Physical examination revealed an erythematous, warm area of skin in the infraclavicular region with surrounding inflammation. The patient appeared otherwise well with no systemic symptoms. The lesion showed characteristics consistent with an inflammatory response to arthropod envenomation. No evidence of tick attachment or classic erythema migrans pattern was observed.

The Diagnostic Journey

Given the patient's history of dermatographia and the persistent nature of the inflammatory response, differential diagnosis included exaggerated arthropod assault response, delayed hypersensitivity reaction, secondary bacterial infection, and early Lyme disease. The patient's certainty that no tick was involved, combined with the clinical presentation, made Lyme disease less likely. Laboratory workup was considered but deferred pending response to initial treatment.

Final Diagnosis

Exaggerated arthropod assault response (papular urticaria) with possible contribution from underlying dermatographic tendency

Treatment Plan

Initial conservative management included discontinuation of ineffective topical hydrocortisone and bilastine antihistamine. Alternative treatment approach with stronger topical anti-inflammatory agents and consideration of systemic corticosteroids if no improvement. Patient education regarding monitoring for signs of secondary infection or systemic symptoms that might warrant re-evaluation for tick-borne illness.

Outcome and Follow-up

Patient advised to monitor lesion for changes in size, development of target-like appearance, or systemic symptoms. Follow-up scheduled if no improvement within 48-72 hours of modified treatment regimen or if any concerning features develop. Emphasis placed on the importance of returning if symptoms worsen or new symptoms emerge.