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Sporotrichosis is a subacute or chronic disease caused
by the dimorphic fungus Sporothrix schenckii.
Geographic distribution: The disease occurs worldwide, but most reported cases have originated
from the United States, South Africa, Mexico, and South America.
Mode of
infection:
Infection
usually results from the traumatic implantation of the fungus, growing
in soil or on plant materials, into the skin and subcutaneous tissue.
In rare
instances, a primary cutaneous infection may disseminate to the bones,
joints, lungs, and other organs.
Even more
rarely, inhalation of the fungus results in primary pulmonary
infection, which may disseminate.
Sporotrichosis is not contagious, but infection can result from
contamination of skin wounds with exudates from humans or animals with
sporotrichosis.
There is no
evidence that underlying disease or immunosuppression predispose to a
person to infection.
Clinical
presentation:
The
most common form of sporotrichosis is lymphocutaneous.
Clinically, this form is manifested as
a chain of subcutaneous nodules along the course of lymphatics
draining a primary skin lesion that may be nodular and ulcerated.
Lymphocutaneous lesions develop within
7 to 90 days or longer after penetrating injury to an exposed part of
the body, such as the hand, arm, neck, or foot.
Eventually, the subcutaneous nodules
soften, ulcerate, and discharge pus.
Solitary, ulcerated, and verrucous
lesions of the skin without lymphatic involvement also occur.
They are sometimes mistaken for a
neoplasm and excised surgically.
Pathological
features:
Image1 ;
Image2 ;
Image3
;
Image4 ;
Image5
(Dr Tsutsumi) ;
S. schenckii usually elicits a mixed
suppurative and granulomatous inflammatory reaction accompanied by
microabscess formation and fibrosis.
This type of inflammation is typical of
all forms of the disease, but it is not specific.
In tissue sections, S. schenckii
appears as spherical, oval, or elongated (cigar-shaped) yeast-like
cells, 2 to 6 micrometer or more in diameter. The fungal cells often bear elongated
buds with narrow-based attachments to the parent cells.
Image Link
(Tulane)
Multiple budding is seen rarely.
Although considered by some to be the
classic tissue form of the fungus, cigar-shaped organisms are not
commonly found. When present, they are most often
observed in disseminated lesions.
Hyphae are rarely found in tissue.
The presence of asteroid bodies (fungal
cells surrounded by Splendor-Hoeppli material) within microabscesses
is helpful in making a presumptive histologic diagnosis of
sporotrichosis.
Image Link(Tulane)
However, the asteroid body is not
pathognomonic for the disease. Splendore-Hoeppli material may surround
parasitic ova, actinomycotic granules, eumycotic granules,
foreign
objects such as silk sutures, and other species of fungi, especially
Coccidioides immitis
, Aspergillus and
Candida
.
In many cases of sporotrichosis,
asteroid bodies cannot be detected.
[
NOTE: Some
authors have
classified the fungal cells in sporotrichosis tissue into the five
categories for correct understanding of the pathological condition in
a sporotrichosis lesion:
(1) fungal cells
in polymorphonuclear leukocyrtes (PMNs) ,
(2) fungal cells
in PMNs within macrophages,
(3) fungal cells
in macrophages,
(4) fungal cells
in giant cells, and
(5) free
fungal cells ].
Diagnosis:
Generally, few S. schenckii cells are
found in cutaneous lesions, and special stains for fungi, complemented
by immuno-flourescence staining, are needed to identify the fungus in
fixed tissues.
When immunoflourescence tests are not
available, microbiologic culture or mouse inoculation is essential for
an accurate diagnosis.
Treatment:
The treatment of choice for sporotrichosis is potassium iodide,
especially for lymphocutaneous infection. Amphotericin B and
other antifungals may also be useful in systemic infection. If
untreated, the infection may persist for years.
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