Page 205 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 6-30 Infectious Diseases

VARICELLA

The varicella-zoster virus (VZV) causes two discrete Hemorrhagic
clinical infections: chickenpox (varicella) and herpes chickenpox
zoster (shingles). Although chickenpox was once a uni-
versal infection of childhood, the incidence of this
disease has plummeted since the advent of the chick-
enpox vaccine. VZV belongs to the herpesvirus family
and is primarily a respiratory disease with skin
manifestations.
Clinical Findings: The disease is seen predominantly
in children and young adults. Disease in adults tends to
be more severe. Varicella is caused by inhalation of the
highly infectious viral particle from an infected contact.
The virus replicates within the pulmonary epithelium
and then disseminates via the bloodstream to the skin
and mucous membranes. Most children do not have
severe pulmonary symptoms. A prodrome of headache,
fever, cough, and malaise may precede the development Varicella pneumonia. Nodular infiltrates
of the rash by a few days. in both lower lobes
The rash of varicella is characteristic and is present in
almost 100% of those infected. It begins as a small,
erythematous macule or papule that vesiculates. After
vesiculation, the lesion may form a small vesiculopustule
and then quickly rupture and form a thin, crusted
erosion. The resulting vesicle has a central depression or
dell, and it is localized over a red base. This gives rise to
the classic description of a “dew drop on a rose petal.”
The rash is more common on the trunk and on the head
and neck, and it often is less severe when found on the
extremities. A characteristic finding is an enanthem.
The mucous membranes of the mouth are frequently
involved with pinpoint vesicles with a surrounding red
halo. A clinical clue to the diagnosis is the finding of
lesions of multiple morphologies occurring at the same
time. Most cases of varicella are self-resolving and heal
with minimal to no scarring. Scarring can be significant Multinucleated giant cell with massive edema
if the vesicles or crusts become secondarily infected. of the alveolus
Children are considered infectious from 1 to 2 days
before the rash breaks out until the last vesicle crusts
over. The diagnosis of chickenpox is made clinically. A
Tzanck test, direct immunofluorescence, or viral culture Pleural
can be used in nonclassic cases to confirm the diagnosis. hemorrhagic
Adults who develop primary varicella infection are at pocks
risk for severe pulmonary complications and severe skin
disease with a dramatically increased risk for scarring.
Adults who are exposed to VZV for the first time are
more likely to develop pneumonia and encephalitis.
Children who develop pneumonia during an infection
with chickenpox have most likely acquired a secondary
bacterial pneumonia.
Since the universal adoption in the United States of
routine childhood vaccination against varicella in 1995,
the incidence of varicella has precipitously dropped.
The VZV vaccine is a live attenuated vaccine that is
highly effective in achieving protective titer levels.
Those individuals who develop chickenpox after vac-
cination have an attenuated course that is manifested by Chickenpox in child; “dew drops on a rose petal”
a few vesicles and more macules. This atypical variant
of chickenpox is often misdiagnosed, or it may be so
mild that the parents do not seek medical care.
Histology: A skin biopsy of a vesicle shows an
intraepidermal blister that forms via ballooning degen- virus invades endothelial cells in the respiratory tract. treatment of secondary bacterial infection. Immuno-
eration of the keratinocytes. There is a perivascular The virus quickly disseminates to the lymphatic tissue compromised individuals, including pregnant women,
lymphocytic infiltrate in the dermis. Multinucleated and then to other organ systems. This virus is neuro- should be treated with an antiviral medication such as
giant cells can be seen at the base of the blister. trophic and can lie dormant in the dorsal root ganglion, acyclovir. Neonates are also at high risk for serious
Pathogenesis: Varicella (chickenpox) is caused by with the potential to reactivate much later in the form disease and need to be treated. The vaccine provides
VZV. This is a double-stranded DNA virus with a lipid of shingles. long-term effectiveness that has been shown to last for
capsule. It is spread from human to human via the Treatment: Most childhood infections require no decades. More time is needed to firmly establish the
respiratory route. Once inhaled, the highly infectious specific therapy other than supportive care and need for and timing of any booster vaccinations.

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