Diagnosing Lyme disease.

The incidence of Lyme disease is increasing, and the disease is spreading geographically. Prompt diagnosis requires recognition of characteristic signs and symptoms of infection with the spirochete Borrelia burgdorferi. In more than half of cases, erythema migrans is the earliest sign of Lyme disease. Although less frequently seen than erythema migrans, peripheral neuropathy of the seventh cranial nerve is another important sign. Tests for Lyme disease await refinement, but laboratory evaluation can be helpful when Lyme disease is suspected.