Page 192 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 6-17 Integumentary System

LYME DISEASE

Lyme disease is a tickborne infection caused by the
spirochete bacteria, Borrelia burgdorferi. The deer tick,
Ixodes scapularis, is the main tick responsible for trans-
mitting the disease to humans. Discovered in 1975 in
the Connecticut town of Lyme, this disease has become
the most common tickborne disease in the United
States. Most cases are reported in the spring, summer, Lyme disease
and early fall, correlating with tick activity. The disease is spread by a
not only affects humans but has been reported to affect bite from an
dogs, horses, and cattle. Ixodes scapularis
Clinical Findings: Erythema migrans is the charac- tick that is
teristic cutaneous rash of Lyme disease. Erythema infected with
migrans typically manifests as a solitary “bull’s-eye” Borrelia
macule at the site of the tick bite. There is a central red burgdorferi.
macule surrounded by nonaffected skin, which is then
entirely surrounded by an expanding erythema that Early disseminated Lyme disease with
blends in with the normal skin. The rash of erythema multiple bull’s-eye lesions of erythema
migrans is larger than 2 cm in diameter. The rash mani- migrans. This is seen in up to 25%
fests soon after the tick has transmitted the bacteria of patients who develop Lyme disease.
into the skin. Occasionally, the central portion of the
lesion forms a vesicle or bulla. Solitary skin lesions
are the most frequent skin manifestation, but one
can also encounter early disseminated Lyme disease. Bell’s Palsy: Common Manifestation of Chronic Lyme Disease
This results in multiple areas of skin involvement. The
numerous skin lesions are smaller than the original Hyperacusis Left peripheral VII facial weakness Left central VII facial weakness
lesion, lighter in color, and not as fully developed as
bull’s-eye lesions. This early dissemination of B. burg- Attempt to close eye results in the
dorferi occurs in one quarter of infected individuals. eyeball rolling superiorly, exposing
Most patients also exhibit constitutional symptoms at sclera (Bell’s phenomenon), but no
the time of diagnosis, including headache, fever, and closure of the lid per se.
malaise.
Erythema migrans occurs in approximately 75% of
those infected with the spirochete. Individuals who do
not exhibit the rash and those who go without treat-
ment are likely to develop chronic disease, which mani-
fests in many ways. Lyme arthritis is one of the most
frequent manifestations of chronic Lyme disease; it is
typically oligoarticular in presentation. Another of the
more frequently seen manifestations is Bell’s palsy,
which is caused by involvement of the central nervous
system. The cardiovascular, nervous, musculoskeletal,
and hematological systems may all be involved in
chronic Lyme disease.
Histology: Skin biopsies of erythema migrans show a This may be an early or initial
lymphocytic superficial and deep dermal infiltrate. symptom of a peripheral VII
Numerous plasma cells may be seen in conjunction with nerve palsy: patient holds Patient has an incomplete smile
eosinophils. Spirochetes are seen in fewer than half of phone away from ear because with very subtle flattening of
specimens. The pathological findings of erythema of painful sensitivity to sound. Patient is unable to wrinkle affected nasolabial fold and
migrans are used to help confirm the clinical findings. Loss of taste also may occur forehead; eyelid droops relative preservation of brow
However, one should not wait for the pathology report on affected side. very slightly; cannot show and forehead movement.
to treat a patient with clinical evidence of Lyme disease. teeth at all on affected side
Pathogenesis: B. burgdorferi is a spirochete that is in attempt to smile; and
transmitted to humans via the bite of the deer tick lower lip droops slightly.
(I. scapularis). The white-tailed deer and the white-
footed mouse are the two reservoirs for B. burgdorferi.
These two animals are typically unaffected by the bac-
teria. The larval, nymph, or adult form of the I. scapu-
laris tick takes a blood meal from one of these reservoirs Treatment: Treatment of erythema migrans consists permethrin can be purchased for those who spend time
and acquires the bacteria. The spirochete causes the of a 3-week course of doxycycline. The therapy is outdoors in endemic areas.
tick no harm and can survive in the gut of the tick for highly effective and has an excellent safety profile. After being in a wooded region, people should check
prolonged periods. The tick can then transmit the bac- Amoxicillin can be used for patients who cannot take their skin for the presence of ticks and remove them
teria to an incidental host such as a human. Trans- doxycycline and for young children. Central nervous immediately, because the transmission of the spirochete
mission of the bacteria is increased the longer the tick system involvement requires intravenous therapy with requires approximately 24 hours of attachment. This
is attached to the host. It is generally believed that ceftriaxone or penicillin. Prevention is critically impor- inspection method works for adult ticks, but the larvae
a tick must be attached for 24 hours to transmit tant. Permethrin-based insect repellants are effective and nymphs are too small to see routinely and are
the bacteria. at repelling deer ticks. Clothing impregnated with almost always overlooked.

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