migrans rash, which is often described as a localized annular lesion with central clearing (Figure 1). 6 During early disseminated disease, the patient may experience a constellation of symptoms including fever, headaches, fatigue, myalgia, facial nerve palsies, and cardiac or neurologic complications (Table 1). 1,5 If left untreated, Lyme disease can lead to a variety of different complications including Lyme arthritis, Lyme carditis, and Lyme neuroborreliosis. Up to 60% of patients with untreated early Lyme disease will develop Lyme arthritis. 5 Lyme arthritis typically is manifested during late disease and can occur weeks or even months after the initial tick bite. 5 Between 4% and 10% of patients with untreated Lyme disease will develop Lyme carditis, which is most commonly seen in patients ages 10 to 45 years. 1,4 Lyme neuroborreliosis is less common in the United States than in Europe, and about 11% of patients with Lyme infection present with neurologic symptoms. 7 LYME ARTHRITISLyme arthritis is the most common complication of late Lyme disease and often presents as monoarthritis of the knee weeks or months after the initial tick bite. 5 It also can present as asymmetric oligoarthritis, most often of the large joints (Table 2). Lyme arthritis is caused by vascular damage, cytotoxic processes, proliferation of fi broblasts, and fi brosis in the joint in response to a proinfl ammatory © DAVID JARA BOGUNYA/SHUTTERSTOCK.COM I n the United States, Lyme disease, a tick-borne illness, is most commonly caused by the spirochete bacteria Borrelia burgdorferi. 1 Although about 30,000 cases are reported each year in the United States, the actual incidence of Lyme disease is about 476,000 cases annually, with most cases occurring in the Northeast and upper Midwest. 2 A missed diagnosis of Lyme disease can lead to a variety of systemic complications and increase patient morbidity and mortality.The incubation period of Lyme disease ranges from 3 to 30 days, with an average of 7 to 14 days. 3 Lyme disease is more common in males and typically follows a bimodal age distribution, occurring most commonly in children ages 5 to 9 years and adults ages 45 to 59 years. 4 The three stages of Lyme disease are early localized, early disseminated, and late disease. 5 In early localized disease, about 80% of patients will experience the classic erythema ABSTRACT Complications of Lyme disease including Lyme arthritis, Lyme carditis, and Lyme neuroborreliosis, typically occur during the early disseminated and late phases of the disease. Clinicians must maintain a high index of suspicion so they can recognize and treat complications promptly. Early treatment with appropriate antibiotics often leads to improved clinical outcomes.