PARACOCCIDIOIDOMYCOSIS
Paracoccidioidomycosis, also known as South American blastomycosis, is a disease that is seen almost exclusively in regions of Central and South America. It is caused by the dimorphic fungus, Paracoccidioides brasiliensis. Most infections are acquired by direct inhalation of the chlamydospores. The fungus is found in the environment in the mycelial or mold phase; it converts to the yeast phase at body temperature. Brazil has the highest incidence of paracoccidioidomycosis. Primary lung infection may lead to disseminated disease, with the skin being secondarily infected. Direct inoculation into the skin causes primary cutaneous disease.
Clinical
Findings: This fungal infection is more common in men than in women, for reasons
poorly understood. It may be that men are more likely to have occupational
exposures (most commonly, farming). A protective effect of estrogen also has
been hypothesized. There is no race predilection. Immunocompetent hosts who are
exposed to the fungus are likely to develop a subclinical infection. Then,
either the fungus becomes walled off in the form of granulomas within the lung
or the patient goes on to develop clinical disease. Serological testing may
show evidence of past exposure in healthy subjects with no clinical findings.
Some hosts have a constellation of flu-like symptoms that include malaise,
weight loss, fatigue, fever, pneumonitis, and pleurisy. Progressive pulmonary
lesions may occur regardless of immune status, but they are more severe in
patients who are immunosuppressed.
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Bilateral
pulmonary infiltrates are seen on chest radiography and are similar to the
radiographic findings of tuberculosis. The infiltrates often form consolidated
areas with cavitations that heal with emphysematous changes. Almost all cases
of paracoccidioidomycosis affect the lung. Once established, the fungus is able
to disseminate to the skin, draining lymph nodes, adrenal glands, central
nervous system, peritoneum, and gastro-intestinal tract.
Skin lesions
in paracoccidioidomycosis come in two distinct varieties. Disseminated disease
is the more frequently encountered subtype. The lesions are predominantly on
the head and neck, especially around the oral and nasal passages. The oral
mucosal membranes and tongue are involved. Nasal and pharyngeal ulcerations are
so frequently encountered that they have been given a name, Aguiar-Pupo
stomatitis. The mucosal lesions are often peppered with pinpoint
hemorrhagic areas. The skin findings may include papules, nodules, or fungating
plaques. Ulceration is almost universal, and patients complain of pain and
swelling. Cervical lymph nodes are enlarged. The infected lymph nodes often
form sinus tracts to the skin and drain spontaneously.
The second
form of cutaneous paracoccidioidomycosis is caused by direct inoculation of the
fungus. The fungal elements are normally found in the soil, and piercing of the
skin with a contaminated object can lead to primary cutaneous
paracoccidioidomycosis. These lesions appear as papules or draining tender
nodules with or without overlying ulceration. Some may spontaneously resolve,
but most slowly enlarge.
Histology:
Skin
biopsy specimens show pseudocarcinomatous hyperplasia of the epidermis with
varying degrees of ulceration and abscess formation. There is a mixed
inflammatory infiltrate. Suppurative granulomatous inflammation is seen within
the underlying dermis. The fungus can be seen on routine hematoxylin and eosin
staining with close inspection. The cells of the yeast phase are thick walled
and refractile. They can be seen in the shape of a “mariner’s wheel,” which is highly characteristic
and specific for P. brasiliensis. The fungus can be highlighted
with a multitude of special staining methods, including periodic acid–Schiff
and sliver stains. The fungus is easily cultured on Sabouraud’s medium and
shows fluffy white colonies.
Pathogenesis:
The
fungus P. brasiliensis has unusual living requirements, and its growth
in the environment is dependent on the soil pH, the altitude, and a consistent
temperature. Alterations in the optimal growing conditions decrease the
survivability of the organism. The host response to this fungus depends on an intact Th1 helper T-cell
response.
Treatment:
Treatment
with itraconazole has had great success and has drastically altered the
prognosis of this disease. As with all systemic fungal infections, treatment
courses last for months to a year. Historically, sulfonamides were used. If
left untreated, this disease has a significant mortality rate. Ketoconazole and
fluconazole have also been used successfully, and amphotericin B is now
reserved for the most severe cases and for those that fail to respond to azole or sulfonamide therapy.
