Chapter 233 Paracoccidioides brasiliensis
Etiology
Paracoccidioidomycosis (South American or Brazilian blastomycosis, Lutz-Splendore-Almeida disease) is an uncommon fungal infection endemic in South America, with cases reported in Central America and Mexico. The etiologic agent, Paracoccidioides brasiliensis, is a thermally dimorphic fungus found in the environment in the mycelial (mold) form and in tissues as yeast.
Epidemiology
P. brasiliensis is ecologically unique to Central and South America. Endemic outbreaks occur mainly in the tropical rain forests of Brazil, with cases scattered in Argentina, Colombia, and Venezuela. There is an increased incidence in areas with moderately high altitude, with high humidity and rainfall, and where coffee and tobacco are grown. Armadillos appear to be a natural reservoir for P. brasiliensis. The most common route of infection is by inhalation of conidia. The disease is not usually thought to be contagious, and person-to-person transmission has not been confirmed. Paracoccidioidomycosis is more common among boys after puberty due to the role of estrogen in preventing the transition of conidia to the yeast form.
Pathogenesis
The entry route into the body is via the respiratory tract, and the lungs are the site of primary infection, although not all patients have respiratory symptoms. Once the conidia reach the alveoli, yeast transformation takes place. The infection then spreads to the mucous membranes of the nose, mouth, and gastrointestinal tract. Cell-mediated immunity, specifically a TH2-type response, is crucial to containing the infection. TNF-α and IFN-γ activated macrophages are responsible for intracellular killing of P. brasiliensis. The yeast can disseminate by the lymphohematogeneous route to skin, lymph nodes, and other organs and remain dormant in lymph nodes, producing a latent infection with reactivation occurring later on in life. There are cases of patients who developed disease 30 or more years after leaving an endemic region.
Histopathologically, the yeastlike cells are round, with the parent cell being quite large and surrounded by small buds, giving it the appearance of a ship’s wheel. A mixed suppurative and granulomatous inflammatory reaction with areas of necrosis are seen in pulmonary infections. In chronic infections fibrosis and calcification may be seen. Mucocutaneous infections are typified by ulceration and pseudoepitheliomatous hyperplasia.

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