Case Study: A 28-Year-Old Male with a Targetoid Rash After Travel

Case at a Glance

A 28-year-old male developed two classic 'bull's-eye' rashes on his leg after returning from a trip to Montana, leading to a clinical diagnosis of early localized Lyme disease.

Patient's Story

A 28-year-old male presented for evaluation of a skin rash on his legs. He had recently returned from a trip to Montana where he had spent time outdoors. Approximately three days prior to seeking medical advice, he noticed what he initially thought were insect bites. These areas subsequently developed into a more distinct rash. The patient reported that the lesions were itchy but denied any other symptoms such as fever, fatigue, headache, or joint pain. He did not recall finding or removing a tick. He was not on any regular medications.

Initial Assessment

On physical examination, the patient was well-appearing and afebrile. Examination of the lower extremities revealed two distinct lesions on one leg. Each lesion was an expanding, annular, erythematous patch with prominent central clearing, creating a classic targetoid or 'bull's-eye' appearance. The lesions were pruritic but not tender to palpation. No eschar or retained arthropod parts were visible. The clinical presentation was highly suggestive of erythema migrans.

The Diagnostic Journey

The patient's recent travel history to a Lyme-endemic area (Montana) combined with the pathognomonic appearance of the rash strongly pointed towards a diagnosis of early localized Lyme disease. The differential diagnosis included tinea corporis (ringworm) or an atypical insect bite reaction, but the classic bull's-eye morphology made these less likely. Given the characteristic erythema migrans rash in a patient with a relevant exposure history, the diagnosis was made on clinical grounds. Serologic testing for Borrelia burgdorferi was deferred, as antibodies may not be detectable in the early stage of the disease, and a clinical diagnosis is sufficient to initiate treatment.

Final Diagnosis

Early Localized Lyme Disease (presenting as Erythema Migrans)

Treatment Plan

Based on the high clinical suspicion for Lyme disease, immediate antibiotic therapy was recommended. The patient was prescribed a standard 14-day course of oral doxycycline. He was counseled on the importance of completing the full course of antibiotics and educated about the potential signs and symptoms of disseminated Lyme disease (e.g., facial palsy, arthritis, carditis), with instructions to seek immediate follow-up if any were to develop.

Outcome and Follow-up

The patient initiated the doxycycline regimen as prescribed. He reported that the itching subsided within a few days, and the rash began to fade progressively. Upon completion of the antibiotic course, the erythema migrans lesions had fully resolved. The patient remained asymptomatic and did not develop any signs of disseminated disease. He was advised on future tick-bite prevention strategies for outdoor activities.