Dr. Greene's Answer
Lyme disease is a bacterial infection caused by a bite from an infected tick. The symptoms in Lyme Disease can be divided into three stages. In the first stage a characteristic skin rash is the most prominent feature; in the second cardiac and neurologic findings predominate; and in the third stage arthritis is the classic symptom.
The classic early manifestation of Lyme disease is a round rash called erythema migrans. The rash usually occurs at the site of the bite 7 to 14 days after the tick bite, though it has occurred as early as 3 days and as long as 32 days later. Without treatment the rash gradually expands (hence the name migrans) to an average of 16 cm in diameter, but may be as large as 68 cm. The rash remains present for at least one to two weeks and usually twice that. At this stage, treatment is very simple, with amoxicillin or doxycycline. The symptoms usually resolve within several days. People with the skin lesions may have no other symptoms, but may also feel fatigue, headache, stiff neck, joint aches and pains, sometimes nausea, vomiting, and sore throat. There is often a low-grade fever, but it can be as high as 104 degrees F with chills.
Neurologic abnormalities occur roughly four weeks after the tick bite, but they can occur as early as two weeks after the bite and up to months or even years later with a wide spectrum of involvement. It may be something as mild as meningeal irritation and headache, but can be as severe as meningitis, encephalitis, chorea, and demyelination. Cardiac abnormalities occur in only about 10% of patients, averaging five weeks after the tick bite and thankfully are relatively brief, lasting no longer than six weeks.
The arthritis of the third stage usually begins five to six weeks after the bite, although it may occur as early as one week afterwards or as late as many months later. Large joints, often those closest to the initial rash, are affected most commonly.
The diagnosis is suspected because of the clinical picture, including the rash and/or flu-like illness in the summer. The diagnosis is confirmed by blood tests, although false negative and false positive blood tests are common.