CAUSES:
• Inhalation of spores of Blastomyces dermatitidis into lung with spread to other organ systems by lymphohematogenous dissemination
• Primary inoculation of skin may rarely occur
• Female genital infection may result from sexual transmission
• Reactivation of previous infection may occur in immunocompromised patients including those with AIDS
--------------------------------------------------------------------------
DIFFERENTIAL DIAGNOSIS
• Pulmonary - acute bacterial pneumonia, tuberculosis, other fungal diseases, bacterial lung abscess, empyema, bronchogenic carcinoma
• Cutaneous - bacterial pyoderma, cutaneous mycobacterial infection, other cutaneous fungal infections (sporotrichosis,histoplasmosis, cryptococcosis), squamous cell carcinoma
• Bone - bacterial osteomyelitis, tuberculosis, neoplastic disease
• Genitourinary - bacterial prostatitis, prostate cancer, other fungal infections, tuberculosis
SPECIAL TESTS:
• Culture of B. dermatitidis from tissue or body secretions on Sabouraud’s or other enriched media
• Demonstration of yeast forms (5-15 micrometers in diameter, with refractile cell wall, broad-based budding and no capsule) in tissue or body secretions by wet
mount or special stains
• In pulmonary disease, KOH prep of sputum reveals organism 50-70% of time
• Serologic tests include complement fixation, enzymelinked immunoassay, immunodiffusion precipitin antibody tests. All have variable sensitivity and low
specificity and are not helpful in diagnosis.
• Delayed hypersensitivity skin testing with blastomycin also has low sensitivity and specifi city and not useful in diagnosis
• Special staining of tissue with Gomori methenamine silver stain
• Periodic acid-Schiff’s stain colors cell wall pink or red
• Mucicarmine stain helps differentiate from encapsulated Cryptococcus
IMAGING:
• CT scan of head for CNS lesions
• CT scan of spine for vertebral lesions
• Bone scan for skeletal lesions
• Chest x-ray may show upper lobe fi bronodular infi ltrates, consolidation, diffuse alveolar infiltrates, mass lesions or pleural thickening
DIAGNOSTIC PROCEDURES:
• Aspiration of abscess contents for wet mount and culture
• Needle or surgical biopsy of involved tissue