ESSENTIALS OF DIAGNOSIS
Lyme borreliosis should be considered in individuals who have a reasonable risk of exposure to Borrelia burgdorferi-infected ticks and who present with a characteristic complex of signs and symptoms.
Classic clinical features occur in stages:
Early localized infection (3–30 days after tick bite): a single hallmark skin lesion erythema migrans (EM), occasionally associated with fever, malaise, headache, arthralgias, and myalgias. These constitutional symptoms can occur in the absence of EM, but this is unusual.
Early disseminated infection (weeks to a few months after tick bite): signs include multiple EM lesions, often with associated fever, migratory arthralgias, and myalgias; carditis manifested primarily as AV nodal block; neurologic features, including cranial nerve palsies (especially involving the facial nerve), lymphocytic meningitis, and radiculoneuropathies.
Late infection (several months to years after tick bite): arthritis, including monoarticular and migratory pauciarticular arthritis; rarely neurologic features such as peripheral neuropathies or chronic mild encephalopathy.
Supporting serologic evidence of exposure to B burgdorferi is present in the majority of cases but can be absent in early infection.
Lyme disease is a multisystem disorder caused by infection with spirochetes of the genus Borrelia burgdorferi sensu lato (sl), most commonly B burgdorferi sensu stricto (ss), B garinii, and B afzelii species. Hard-shelled ticks of the Ixodidae family—Ixodes scapularis and I pacificus in the United States, I ricinus in Europe, and I persulcatus in Asia—serve as vectors for infection. In Europe and Asia, B garinii and B afzelii are the main etiologic agents of Lyme borreliosis, and cases due to B burgdorferi sensu stricto are less common. In contrast, B burgdorferi sensu stricto is responsible for virtually all cases of Lyme disease in the United States. The major exception to this rule is the small number of infections associated with a new species, B mayonii, recently identified in the upper Midwest (Minnesota, Wisconsin, and North Dakota). The specific B burgdorferi sl species causing infection influences the prevalence of certain disease manifestations. As examples, neurologic disease is more common with B garinii, late skin disease is more common with B afzelii, and arthritis is more common with B burgdorferi ss. B mayonii infection may exhibit atypical features described later.
Lyme borreliosis first came to medical attention in the United States in 1975, with the investigation of a clustering of childhood arthritis in the region around Lyme, Connecticut. Lyme arthritis, as it was initially termed, was soon found to be one manifestation of systemic infection with B burgdorferi. The earliest clinical sign reported by patients was a characteristic skin lesion erythema migrans (EM) at the site of a tick bite. In Europe, EM had been associated with I ricinus tick bites since the early twentieth century, and the skin disease was treated successfully with penicillin after spirochetes were visualized in biopsy specimens in the mid-1900s. Other systemic manifestations were occasionally ...