Expanding Erythematous Lesion Following Forest Exposure: Concern for Tick-Borne Illness

Case at a Glance

A 26-year-old woman presents with a rapidly expanding erythematous lesion on her skin following recent forest exposure during mushroom foraging activities.

Patient's Story

The patient reports spending Friday through Sunday engaged in outdoor activities, specifically foraging for mushrooms in wooded areas. Despite conducting tick checks with her spouse's assistance following outdoor exposure, no attached ticks were identified. She noticed the development of what initially appeared to be an insect bite that has progressively worsened over the course of the day. The patient has a medical history significant for attention deficit hyperactivity disorder and depression, currently managed with lisdexamfetamine 20-30mg daily and vortioxetine 15mg daily. She attempted self-treatment with loratadine and topical hydrocortisone 2.5% without improvement.

Initial Assessment

Patient presents with concern for possible tick-borne illness, specifically Lyme disease, given recent forest exposure and development of an expanding skin lesion. Physical examination reveals an erythematous lesion that has demonstrated rapid expansion over several hours, documented with photographic evidence showing progression from 17:17 to 20:20 on the day of presentation.

The Diagnostic Journey

Initial clinical suspicion focused on arthropod bite reaction versus early cutaneous manifestation of tick-borne illness. The absence of confirmed tick attachment raised questions about the likelihood of Lyme disease, as most cases require prolonged tick attachment (12-24 hours or more). Differential diagnosis included erythema migrans, cellulitis, arthropod bite reaction, or other dermatologic conditions.

Final Diagnosis

Pending clinical evaluation and potential serologic testing for tick-borne illnesses. The expanding nature of the lesion warrants consideration of erythema migrans despite absence of confirmed tick bite.

Treatment Plan

Patient advised to seek prompt medical evaluation given the progressive nature of the lesion. Clinical assessment would determine need for empirical antibiotic therapy pending diagnostic workup. Discontinuation of ineffective topical treatments recommended pending professional medical evaluation.

Outcome and Follow-up

Patient scheduled for urgent medical evaluation. Clinical response to be monitored with consideration for dermatologic or infectious disease consultation if initial assessment inconclusive. Patient education provided regarding tick-borne illness prevention for future outdoor activities.