A 28-year-old trekker returns from a forested area and notices an annular, slowly expanding red plaque with central clearing on his calf, appearing at the site of a tick bite sustained 12 days earlier. He is otherwise well. This lesion represents which stage of Lyme disease?

• A Stage 3: persistent late infection
• B Stage 2: disseminated infection
• C Stage 1: localised infection ✓
• D Stage 4: autoimmune post-infectious phase

Explanation

Erythema migrans, an expanding annular plaque with central clearing at the tick bite site appearing 3 to 30 days after inoculation, is the hallmark of stage 1 (localised) Lyme borreliosis caused by Borrelia burgdorferi transmitted by Ixodes ticks. Disseminated disease (stage 2) brings multiple lesions, cranial neuropathy and carditis, while stage 3 features arthritis and acrodermatitis chronica atrophicans.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.