• Clinical course can be prolonged and may involve multiple organ systems.
  • Cutaneous hallmarks are erythema migrans
  • Image not available.

    A 32-year-old woman presents having had 5 days of low-grade fevers and the typical eruption of erythema migrans on her upper back. Note the expanding annular lesion with a target-like morphology. (Courtesy of Thomas Corson, MD.)

    and acrodermatitis chronica atrophicans.
  • Diagnosis is typically made on clinical grounds, identification of the organism from tissue sections and/or serologic testing.





  • Lyme disease is caused by Borrelia burgdorferi, a spirochete.
  • Burgdorfer isolated a new spirochetal bacterium, Borrelia burgdorferi, from the midgut of the Ixodes dammini tick (now Ixodes scapularis).3 
  • Recovery of the organism subsequently from cutaneous lesions, cerebrospinal fluid (CSF), and blood specimens of patients with Lyme disease in both the United States4,5 and Europe68 definitively linked the disease with B. burgdorferi.


Development of a specific humoral immune response generally occurs over weeks to months.47,48 The IgM response usually peaks between 3 and 6 weeks after disease onset and may remain elevated for months to years; the immunoglobulin G (IgG) response usually follows the IgM response by several weeks so that approximately 90% of patients have detectable IgG levels 4–6 weeks into the infection. The development of the humoral antibody response typically heralds a significant decrease in the number of organisms and decrease in the level of inflammation. Of note, the acquired humoral response is not typically protective against reinfection, in part due to significant sequence variability in protective antigenic epitopes between B. burgdorferi strains and the lack of expression of less variable protective antigens (e.g., OspA) in the mammalian host.49

Table 53-1. 

Tick (Common Name/Species Name) Primary Range Transmits Additional Facts
Black-legged tick/deer tick (Ixodes scapularis) Northeastern USA, Great Lakes region Lyme, HGA, babesiosis Can remain active in warmer winters
Western black-legged tick (Ixodes pacificus) Pacific Coast, particularly northern CA Lyme, HGA Rates of infection are low
American dog tick (Dermacentor variabilis) East of Rockies RMSF Also known as wood tick
Rocky Mountain wood tick (Dermacentor andersoni) Rocky Mountain states RMSF Live in elevations 4000–10,500 feet
Lone Star tick (Amblyomma americanum) Southeast USA, but can be Texas to Maine Ehrlichiosis Bites can be particularly irritating
Brown dog tick (Rhipicephalus sanguineus) Throughout USA RMSF Primary host–dogs

HGA, human granulocytic anaplasmosis; RMSF, Rocky Mountain Spotted Fever.



Lyme borreliosis, or Lyme disease, is the most commonly reported arthropod-borne illness in both the United States and Europe.1 It was first recognized in the 1970s after epidemiologic investigations of a clustering of cases of oligoarthritis among children in eastern Connecticut established a probable microbial etiology for the disease.2 In 1981,

The incidence and range of the organism has steadily grown since its recognition in the 1970s. Deer and birds are thought to be the primary drivers in dispersal of infected ticks into new areas.

 In 2006, the number of new cases in the United States was 19,931 (national median incidence 0.5 cases per 100,000 people). This represents a 101% increase in annual incidence since 1992. There is believed to be significant underreporting of Lyme disease, and the real number of new cases each year in the United States is actually thought to approach 150,000. For the 15-year period for which the CDC has data, approximately 93% of reported cases occurred in ten states located in the Northeastern, mid-Atlantic, and North Central regions: Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Wisconsin. Nearly all states have reported cases of Lyme disease at some point during the past 15 years, though average incidence varies markedly from 0.0 for Colorado, Montana, and Hawaii to 73.6 per 100,000 people for Connecticut. Disease in many of the states with low incidence represents travelers infected during travel to more endemic regions.

Lyme disease is also widely distributed in Europe, with an estimated 120,000 new cases each year.11 The highest reported frequencies occur in forested areas of central and Northern Europe (Germany, Austria, Slovenia, and Sweden).12,13 

The infection is also found in Eastern Russia, China, Korea, and Japan.14



Treatment options for those presenting with erythema migrans are doxycycline, cefuroxime, and amoxicillin for a ≥14-day course.

Intravenous dosing with cetriaxone, cefotaxime, and penicillin G is indicated in patients with central nervous system (CNS) and cardiac manifestations.

Arthritis manifestations without CNS manifestations can be treated with the aforementioned oral medications for 28 days



Complications of Injecting Drug Use

  • Local problems—Abscess (Figures 240-2 
    Image not available.

    A 32-year-old woman with type 1 diabetes developed large abscesses all over her body secondary to injection of cocaine and heroin. Her back shows the large scars remaining after the healing of these abscesses. (Courtesy of ­Richard P. Usatine, MD.)

    and 240-3; Abscess), cellulitis, septic thrombophlebitis, local induration, necrotizing fasciitis, gas gangrene, pyomyositis, mycotic aneurysm, compartmental syndromes, and foreign bodies (e.g., broken needle parts) in local areas.2
    • IDUs are at higher risk of getting methicillin-resistant Staphylococcus aureus(MRSA) skin infections that the patient may think are spider bites (Figure 240-4).
    • Some IDUs give up trying to inject into their veins and put the cocaine directly into the skin. This causes local skin necrosis that produces round atrophic scars (Figure 240-5).
  • IDUs are at risk for contracting systemic infections, including HIV and hepatitis B or hepatitis C.
    • Injecting drug users are at risk of endocarditis, osteomyelitis (Figures 240-6and 240-7), and an abscess of the epidural region. These infections can lead to long hospitalizations for intravenous antibiotics. The endocarditis that occurs in IDUs involves the right-sided heart valves (see Chapter 50, Bacterial Endocarditis).2 They are also at risk of septic emboli to the lungs, group A β-hemolytic streptococcal septicemia, septic arthritis, and candidal and other fungal infections.


Prognosis for Lyme is good, especially with early treatment. Even if disease progresses to disseminated stage, disability is uncommon. Treatment at any stage portends a high likelihood of symptom resolution, but lasting symptoms typically consist of arthralgias and/or sensory deficits (CN VII).

Chronic Lyme disease is a separate entity with symptoms typically consisting of musculoskeletal pain and fatigue. Chronic or posttreatment Lyme continues to be an area of controversy. Studies are ongoing as to potential etiologies, but continued antibiotic treatment after resolution of active disease is not indicated.

Content 13

Content 11


A 42-year-old surveyor from Connecticut presents with a 2 day history of the rash shown below. Which of the following signs or symptoms is also likely to develop in this patient?

Image not available.

FIGURE II-27 Reprinted from KJ Knoop et al: The Atlas of Emergency Medicine, 4th ed. New York, McGraw-Hill, 2016. Photo contributor: James Gathany, Public Health Image Library, US Centers for Disease Control and Prevention.


Complete Quiz and View Results
You will be able to view all answers at the end of your quiz.

The correct answer is C. You answered D.

The answer is C. (Chap. 25e) This is a classic picture of erythema migrans due to B burgdorferi, or Lyme disease. The rash is an early manifestation of Lyme disease and is characterized by erythematous annular patches, often with a central erythematous focus at the tick bite site. The sequelae of Lyme disease are myriad and include CNS, articular, and cardiac complications. One of the classic cardiac complications is conduction system disease, most concerning the possibility of progression to complete heart block. Option B describes the classic cutaneous manifestations of Kawasaki disease, most commonly seen in children. When seen in conjunction with painful or nonpainful purpuric lesions on the hands or feet, the murmur of mitral regurgitation would suggest infectious endocarditis (option A). Option D describes a toxic shock syndrome, which is unlikely in this patient with erythema migrans. Option E describes Koplik spots, the pathognomic buccal mucosal finding in measles.


Infection by what organism causes the rash shown berlow?

Image not available.

FIGURE IV-166 Courtesy of Vijay K. Sikand, MD; with permission.


Next Question
You will be able to view all answers at the end of your quiz.

The correct answer is C. You answered C.

The answer is C.(Chap. 210) The picture shows the characteristic rash of erythema migrans, the defining lesion of Lyme disease caused by B burgdorferi. Erythema migrans appears at the site of the tick bite within 3–32 days following the initial bite. It typically begins as a red macule or papule and expands slowly to form an annular lesion. As the lesion gets larger, the classic targetoid appearance develops with bright red outer ring as well as ongoing erythema at the central lesion with clearing in between. The most common sites of erythema migrans are the classic locations of tick bites, including the groin, axilla, and thigh. The presence of this lesion in an endemic area for Lyme disease is an indication for treatment and does not require serologic confirmation. Anaplasma phagocytophilum is the causative organism of human granulocytic anaplasmosis. This rickettsial disease is also transmitted through a tick bite and is prevalent in the upper Midwest, New England, parts of the Mid-Atlantic, and northern California. Rash occurs in about 6% of cases, although no specific rash is identified. The most common manifestations are fevers, malaise, and myalgia. B henselae (option B) is the organism responsible for cat-scratch fever, which can present with mild erythema near the site of the injury and markedly enlarged lymph nodes. Ehrlichia chaffeensis is another rickettsial organism that is transmitted by the bite of a tick and is common is in the southeast, northeast, Texas, and California. Human monocytic ehrlichiosis is the disease caused by the organism and presents with nonspecific symptoms of fever, malaise, and myalgia. Rash is also not common in ehrlichiosis. Rickettsia rickettsii is the rickettsial organism responsible for Rocky Mountain spotted fever (RMSF). About 90% of individuals with RMSF have a rash during the course of the illness. The rash most commonly presents with diffuse macules beginning on the wrists and ankles and spreading to the trunk.

68% of users answered correctly.


Content 3

Question 1 of 10

B burgdorferi serology testing is indicated for which of the following patients, all of whom reside in Lyme-endemic regions?

Next Question
You will be able to view all answers at the end of your quiz.

The correct answer is A. You answered D.

The answer is A. (Chap. 210) Lyme serology tests should be done only in patients with an intermediate pretest probability of having Lyme disease. (See Table IV-168.)

 TABLE IV-168 Algorithm For Testing for and Treating Lyme Disease 
View Large |  
Favorite Table | Download (.pdf)

The presence of erythema migrans in both patient B and patient E is diagnostic of Lyme disease in the correct epidemiologic context. The diagnosis is entirely clinical. Patient C’s clinical course sounds more consistent with systemic lupus erythematosus, and initial laboratory evaluation should focus on this diagnosis. Patients with chronic fatigue, myalgias, and cognitive change are occasionally concerned about Lyme disease as a potential etiology for their symptoms. However, the pretest probability of Lyme is low in these patients, assuming the absence of antecedent erythema migrans, and a positive serology is unlikely to be a true positive test. Lyme arthritis typically occurs months after the initial infection and occurs in approximately 60% of untreated patients. The typical attack is large joint, oligoarticular, and intermittent, lasting weeks at a time. Oligoarticular arthritis carries a broad differential diagnosis including sarcoidosis, spondyloarthropathy, rheumatoid arthritis, psoriatic arthritis, and Lyme disease. Lyme serology is appropriate in this situation. Patients with Lyme arthritis usually have the highest IgG antibody responses seen in the infection.

ABLE IV-168 Algorithm For Testing for and Treating Lyme Disease

Pretest Probability Example Recommendation
High Patients with erythema migrans Empirical antibiotic treatment without serologic testing
Intermediate Patients with oligoarticular arthritis Serologic testing and antibiotic treatment if test results are positive
Low Patients with nonspecific symptoms (myalgias, arthralgias, fatigue) Neither serologic testing nor antibiotic treatment

Source: Adapted from the recommendations of the American College of Physicians (G Nichol et al: Ann Intern Med 128:37, 1998, with permission).

USMLE Reviewer (Subscription Required)