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Sporotrichosis is an uncommon, chronic
mycosis caused by Sporothrix schenckii. This ubiquitous
plant saprophyte is a dimorphic fungus that grows as a mold at room
temperature and as a yeastlike form in tissue. Although distributed
worldwide, it is found most commonly in warm, highly humid regions
and in temperate climates. Mexico, other parts of Central America,
Asia, the United States, Canada, and France are endemic areas. Infection
is characterized by isolated cutaneous or subcutaneous necrotizing
nodules associated with the indolent development of suppurating
nodules along the course of the proximal lymphatics. Extracutaneous
and pulmonary forms of the disease occur infrequently. The histopathologic
findings of primary cutaneous disease combine features of both granulomatous
and pyogenic inflammation. Granulomatous lesions consist of aggregations
of epithelioid histiocytes with central areas of necrosis and neutrophils
or zones of Langhans giant cells associated with fibroblasts and
lymphocytes. Occasionally, areas of microabscesses unassociated
with granulomatous reaction may be seen. In chronic disease, pseudoepitheliomatous
hyperplasia may be extensive and mimic neoplasm. A common histopathological
feature is the asteroid body, a round basophilic, yeastlike structure
surrounded by rays of eosinophilic material thought to represent
antigen-antibody complexes. The asteroid body may also be seen in
other mycoses.
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In 95% of cases, the organism is percutaneously inoculated
by contaminated thorns, tree bark, splinters, or animal bites.1 Rare
cases of human-to-human transmission have been reported. Sporotrichosis
has been reported in many areas of the United States but is most common
along the Mississippi River Valley and in the Plains states. Most
cases are sporadic, but outbreaks have been attributed to a single
source.2-4 Infection occurs in all age groups;
about 10% to 25% of cases occur in children.
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Clinical Manifestations
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The spectrum of clinical findings in sporotrichosis can be divided
into lymphocutaneous, fixed cutaneous, extracutaneous (localized
or multifocal), and pulmonary. Cutaneous infection is most common
in children; documented localized extracutaneous infections are
rare.
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Lymphocutaneous sporotrichosis accounts for 75% of infections.
Following inoculation, the average incubation period is 3 weeks
but ranges from 5 days to 6 months. Lesions usually involve the
upper extremities but may occur on the face and trunk.5 The
primary lesion is a firm, mobile, nontender subcutaneous nodule
that enlarges and becomes discolored (Fig. 303-1).
After 2 weeks, it undergoes necrosis, leaving a painless ulcer.
During the next several weeks, additional lesions develop along
the proximal lymphatics; intervening lymphatic channels become thickened,
with overlying cutaneous erythema (Fig. 303-2). Lesions
can persist for months to years. Few heal spontaneously, with scarring
of the ulcers. Systemic symptoms are absent or mild.
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