Lyme disease is a multisystem illness caused by infection with the
spirochete Borrelia burgdorferi and the body's immune response to the
infection. The disease is transmitted to humans via tick bites, from
infected ticks of the genus Ixodes.
Signs and symptoms
Signs and symptoms of Lyme disease vary by disease stage. Physical
findings in patients with early disease are as follows:
- Erythema migrans (EM) - Rash
- Tender local adenopathy (local, not diffuse)
Physical findings in patients with early disseminated disease are as
- EM (single or multiple lesions)
- Tender adenopathy (regional or generalized)
- Conjunctivitis (uncommon, never prominent)
- Carditis (usually manifests as heart block)
- Meningismus as a sign of aseptic meningitis
- Cranioneuropathy, especially cranial nerve VII and Bell palsy
(peripheral seventh nerve palsy with decreased unilateral function,
including the forehead)
In patients with late disease, the typical physical finding is arthritis.
Arthritis is located mostly in large joints, especially the knee. Warmth,
swelling from effusion, and limited range of motion help distinguish
arthritis from simple arthralgia.
See Clinical Presentation for more detail.
In endemic areas, patients with probable erythema migrans and a recent
source of tick exposure should be started on treatment without blood
tests. For serologic testing, the CDC recommends a two-tier testing
procedure, as follows :
- Step 1: EIA or ELISA - Total Lyme titer or IgG and IgM titers
- Step 2: Western blot testing
Western blot testing is performed only if step 1 test results are
positive or equivocal. If signs and symptoms have been present for 30
days or less, both IgM and IgG Western blot testing are performed; if
signs and symptoms have been present for more than 30 days, only IgG
Western blot testing is performed.
Since there is no reason to perform a titer without a confirmatory test
if positive, Lyme titers should always be ordered with a reflex
confirmatory test. In most cases, this should be a Western blot. Most
commercial laboratories will perform both IgG and IgM Western blots. If
the patient has been in Europe, where different strains of Borrelia are
more common, a C6 peptide ELISA is a more accurate confirmatory test than
the Western blots, which have been developed to B burgdorferi, which is
the strain found in the United States. The C6 peptide is less expensive
than the Western blots and is as sensitive and specific for B
burgdorferi; it is a reasonable alternative for the Western blots, but
has not replaced it as the usual confirmatory test in the United States
Ticks can carry more than one disease at a time, so it's possible to
contract multiple infections from just one bite.
Like Lyme, many tick-borne infections have flu-like symptoms such as
fever and headache which makes diagnosis difficult.
Lyme treatment is complicated by co-infections. Patients with
co-infections often don't respond well to the usual treatments, and it
takes an experienced doctor to properly identify and treat each
tick-borne infection. Co-infection generally results in more severe
illness, more symptoms, and a longer recovery
As part of testing for the infections associated with lyme disease, in
addition to Lyme serology, a battery of tests is performed to other
coinfections and other bacterial and viral pathogens that have been
associated with diseases with 'chronic fatigue' manifestiations.
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