Lyme Disease Presenting as a Dermal Hypersensitivity Reaction

Background: Lyme disease is a well-recognized illness commonly associated with skin manifestations such as erythema migrans. However, atypical presentations can complicate diagnosis, particularly when they deviate from classic clinical and histological findings. Methods: We report a potential case of Lyme disease presenting as a dermal hypersensitivity reaction (DHR), with clinical findings resembling urticaria rather than urticarial vasculitis. Skin biopsy findings were reviewed, and Lyme serology testing was performed. Results: The biopsy did not demonstrate the characteristic superficial perivascular lymphocytic infiltrate typically seen with erythema migrans. The patient's history included prior tick exposures, but while Lyme IgM was positive, the Lyme IgG testing was negative, suggesting no prior Lyme exposure. With PCR and repeat IgG scheduled the patient was diagnosed with Lyme disease. Conclusions: This case highlights an atypical presentation of potential Lyme disease and underscores the importance of considering Lyme disease in the differential diagnosis of DHR, especially in patients with a history of tick exposure. In cases of DHR, a thorough clinical history regarding arthropod bites and tick exposure should guide targeted testing for Lyme and other tick-borne illnesses. Keywords: Lyme disease, dermal hypersensitivity reaction, erythema migrans, atypical presentation, tick-borne disease