PARACOCCIDIOIDOMYCOSIS
Paracoccidioidomycosis, formerly known as South American blastomycosis, is caused by inhalation of the spores of a thermally dimorphic fungus, Paracoccidioides brasiliensis. The organism lives in soil or on vegetable matter in a mycelial form and can be cultured in this phase on Sabouraud glucose agar at room temperature. After gaining entry into the body, the fungus is transformed into a yeast, which reproduces itself by the formation of multiple buds. However, organisms with single buds are also observed. The yeast form of the fungus can be cultured on blood agar at 37˚C but is not infectious.
The disease is limited geographically to Latin
America, from Mexico to Argentina, with 80% of the cases occurring in Brazil.
Even in an endemic country, the disease is not distributed homogeneously,
likely reflecting environmental conditions that favor fungal growth. Because the
chronic form of the disease may have a very long incubation period (30 years),
cases have been detected in former residents of areas where it is endemic after
they have lived for years in Europe or the United States. Under these
circumstances, the disease has often been confused initially with tuberculosis
or other mycoses.
Soil is the likely natural habitat of P.
brasiliensis, which relates to a high incidence of agricultural or
construction exposure in patients with this infection. Children account for
less than 10% of the cases with no gender predilection, but in adults, a
striking male predominance, as high as 15:1, is seen. Smoking appears to be a
risk factor for disease in adults.
Clinical presentations of the disease include a
chronic “adult” form in the majority, an acute-subacute “juvenile” form in 15%
to 20%, and a recently described acute disseminated form in HIV-positive
patients. The latter two presentations occur in younger individuals and mainly
involve the reticuloendothelial system with little pulmonary manifestations.
The chronic form usually occurs in individuals 40 to 60 years of age and is
almost always a multifocal disease with predominant pulmonary involvement.
Pulmonary symptoms of dyspnea, cough, and sputum are chronic and nonspecific.
Often on physical examination, abnormalities are lacking despite significant
radiologic findings. Chest radiographs usually show bilateral, symmetric
alveolointerstitial or interstitial infiltrates in the lower and central lung
zones, sparing the apices, with occasional areas of small cavitations.
High-resolution computed tomography scans show a variety of findings, including
ground-glass attenuation, nodules, cavitated nodules, interlobular septal
thickening, and architectural distortion. After treatment, residual fibrosis is
seen in 50% and bullous disease in 25% of patients.
Lesions of the upper airway mucous membranes
(oropharyngeal, laryngeal, and nasal) are common in paracoccidioidomycosis.
They are painful, hyperemic, and covered with small hemorrhagic dots
(mulberry-like) and tend to be progressive and destructive. Draining (submental
and cervical) lymph nodes are often enlarged. Dissemination to the skin, bones,
adrenal glands, central nervous system,
gastrointestinal tract, and gonads may occur with corresponding clinical
manifestations.
Definitive diagnosis depends on demonstration of the
causative organism by direct visualization in infected tissues as 6- to 40-m
yeast cells with multiple buds or by isolation in culture. Antibody and antigen
detection tests are helpful adjuncts to diagnosis and guides to prognosis and
therapeutic response.
TREATMENT
The azoles, specifically itraconazole, are the
treatment of choice for this infection, with a 95% response rate with a 6-month
course. Although sulfonamides, especially trimethoprim/sulfamethoxazole, are
effective for paracoccidioidomycosis, these agents must be administered for very
long periods (3 years), and relapse is frequent. Amphotericin B should be
reserved for critically ill patients.
