Lyme disease is caused by the spirochete Borrelia burgdorferi. Carried by the minute tick Ixodes dammini (or another tick in the
Ixodidae family), the disease occurs when a tick injects spirochete-laden saliva into the bloodstream or deposits fecal matter on the skin. After incubating for 3 to 32 days, the spirochetes migrate outward on the skin, causing a rash and disseminating to other skin sites or organs by the bloodstream or lymph system. The spirochetes’ life cycle is incompletely understood; they may survive for years in the joints, or they may die after triggering an inflammatory response in the host.

Myocarditis, pericarditis, arrhythmias, heart block, meningitis, encephalitis, cranial or peripheral neuropathies, and arthritis are among the known complications of Lyme disease.

Your assessment findings may be deceptive. Patient complaints vary in frequency and severity, probably because the illness typically occurs in stages.

The patient’s history may reveal recent exposure to ticks—especially if he lives, works, or plays in wooded areas where Lyme disease is endemic. And he may report the onset of symptoms in warmer months. Typically reported symptoms include fatigue, malaise, and migratory myalgias and arthralgias. Nearly 10% of patients report cardiac symptoms, such as palpitations and mild dyspnea, especially in the early stage. Severe headache and stiff neck, suggestive of meningeal irritation, also may occur in the early stage when the rash erupts. At a later stage, the patient may report neurologic symptoms such as memory loss.

You may see erythema chronicum migrans, which begins as a red macule or papule at the tick bite site and may grow as large as 2″ (5 cm) in diameter. The patient may describe the lesion as hot and pruritic. Characteristic lesions (not seen in all patients) have bright red outer rims and white centers. They usually appear on the axillae, thighs, and groin. Within a few days, other lesions may erupt, as may a migratory, ringlike rash and conjunctivitis. In 3 to 4 weeks, the lesions fade to small red blotches, which persist for several more weeks.

Bell’s palsy may be seen in the second stage and may occur alone. In the later stage, inspection may disclose signs and symptoms of intermittent arthritis: joint swelling, redness, and limited movement. Typically, the disease affects one or only a few joints, especially large ones such as the knee.