4. Central nervous system: 5-6% normal host; 45% AIDS patients; meningitis and abscess formation
B. dermatitidis exists in warm, moist soil that is rich in organic material. When these microfoci are disturbed, the aerosolized spores or conidia are inhaled into the
lungs. Disease at other sites is a result of dissemination from the initial pulmonary infection; the latter may be acute or chronic.
• Bronchogenic carcinoma
• Bacterial pneumonia
• Pyoderma gangrenosum
• Mycobacterium marinum infection
• Squamous cell carcinoma
• Giant keratoacanthoma
• Physical examination and laboratory evaluation
• Definitive diagnosis established by culture
• Presumptive diagnosis can be made by visualizing the distinctive yeast forms in clinical specimens.
• Culture: on Sabouraud’s or more enriched media
1. Aspirated material from abscesses
2. Skin scrapings
3. Prostatic secretions (urine culture with prostatic massage)
• Direct examination of clinical specimens
1. Wet preparation with 10-12% KOH
2. Histopathology: typically demonstrates pyogranulomas; yeast identification requires special stains
• Serologic tests: currently, a negative serologic test cannot be used to exclude blastomycosis, nor should a positive titer be an indication to start treatment.
In chronic disease, chest radiographic findings are nonspecific but lobar or segmental alveolar infiltrates, especially of the upper lobes, are most common and may
progress to cavitation.
Acute pulmonary infection is usually diagnosed in association with point-source outbreaks and is accompanied by the abrupt onset of fever, chills, pleuritic chest pain,
arthralgias, and myalgias. Cough is initially nonproductive but frequently becomes purulent as disease progresses. Chest radiographs usually reveal alveolar infiltrates
with consolidation. Pleural effusions and hilar adenopathy are uncommon. Most patients diagnosed with pulmonary blastomycosis have chronic indolent pneumonia
with signs and symptoms of fever, weight loss, productive cough, and hemoptysis. The most common radiologic findings are alveolar infiltrates with or without
cavitation, mass lesions that mimic bronchogenic carcinoma, and fibronodular infiltrates. Respiratory failure (adult respiratory distress syndrome) associated with
miliary disease or diffuse pulmonary infiltrates is more common among immunocompromised patients, especially those in the late stages of AIDS. Mortality rates are
≥ 50% among these patients, and most deaths occur within the first few days of therapy. Skin disease is the most common extrapulmonary manifestation of
blastomycosis. Two types of skin lesions occur: verrucous (more common) and ulcerative. Osteomyelitis is associated with as many as onefourth of B. dermatitidis
infections. The vertebrae, pelvis, sacrum, skull, ribs, or long bones are most frequently involved. Patients with B. dermatitidis osteomyelitis often present with
contiguous soft-tissue abscesses or chronic draining sinuses. In men, blastomycosis may involve the prostate and epididymis. Central nervous system (CNS) disease
occurs in < 7% of immunocompetent patients with blastomycosis. In AIDS patients, however, CNS disease has been reported in ~ 45% of cases, usually presenting
as a brain abscess. Less common forms of CNS disease are cranial or spinal epidural abscess and meningitis.
• Indication for chemotherapy remains controversial in patients with acute pulmonary blastomycosis.
• Since the acute form may be benign and self-limited, patients may be closely observed.
• Some patients progress to chronic infection with attendant significant morbidity and therefore may require treatment.
• Patients who are immunocompromised, or have extrapulmonary disease or progressive pulmonary disease should be treated.