Lyme disease typically begins in the spring or summer months, with a pathognomonic skin lesion and associated flulike or meningitislike symptoms. If the patient is not treated during this early stage, cardiac, neurologic, or musculoskeletal manifestations may occur weeks to months later. Although the clinical picture of Lyme disease is extremely variable, the diagnosis can be made in most cases by recognizing the typical patterns of organ involvement and associated immunologic abnormalities.