Typical rash of Lyme disease
In 80% to 90% of patients with Lyme borreliosis in the United States, the disease begins with ECM, which usually occurs at the site of the tick bite. ECM is most frequently found in the groin, axilla, waist, back, and legs. In children the head is also a common site. ECM begins as a red macule or papule that expands to form a large annular lesion measuring ≥20 cm in diameter. Classically, it has an area of central clearing and a bright red outer border ( Fig. 39.2 ), but more commonly lesions are uniform in color or have enhanced central erythema. An ECM-like lesion can also be a sign of Southern tick-associated rash illness associated with the Lone Star tick, Amblyomma americanum.
