Erythema migrans: a spectrum of histopathologic changes

Area of Science:

• Dermatology
• Infectious Diseases
• Pathology

Background:

• Early cutaneous Lyme disease, erythema migrans, is characterized by a distinctive skin rash following a tick bite.
• Standard histopathology typically shows a perivascular lymphocytic infiltrate with plasma cells and eosinophils.
• Deviations from typical findings can complicate diagnosis.

Observation:

• This study examined four confirmed erythema migrans cases with atypical histopathologic features.
• Biopsies, taken from the lesion periphery, revealed variations including peripheral eosinophils/neutrophils, interface changes, and spongiosis.
• Notably, plasma cells were absent in all examined cases.

Findings:

• Erythema migrans can exhibit unconventional histopathologic patterns, including peripheral neutrophils/eosinophils and interface changes.
• The absence of plasma cells, a classic diagnostic marker, was observed in all presented cases.
• These variations highlight the nonspecific nature of histopathologic changes in early Lyme disease.

Implications:

• Dermatopathologists must consider erythema migrans in biopsies showing expanding annular lesions, even with atypical histopathology.
• Serologic confirmation may be essential for diagnosing Lyme disease when histopathologic findings are unconventional.
• Recognizing these varied patterns improves diagnostic accuracy for early cutaneous Lyme disease.