ABSTRACT
Stage 1 is characterized by ECM and nonspecific influenza-like symptoms that occur 3 to 32 days after exposure to ticks. ECM itself begins as an erythematous papule or macule, which gradually becomes an annular lesion that can be many centimeters wide. Some lesions are less distinctive. Secondary lesions may occur at a distance from the original tick bite. Stage 2 often occurs weeks to months after stage 1. Neurologic or cardiac abnormalities develop in 15% and 8% of cases, respectively. Patients may have signs of meningitis, encephalitis, cranial neuritis, motor or sensory radiculoneuritis, and possibly myelitis. Either tachycardia or bradycardia may occur, in association with variable degrees of atrioventricular nodal block. Rarely is there evidence of pericarditis or myocarditis. Stage 3, typified by arthritis, occurs in about 60% of cases. Synovitis may first be manifested weeks to years after ECM. Characteristically, the synovitis affects the knees, but other large joints may be involved as well.
