Blastomycosis: Endemic Fungal Infection – Symptoms, Diagnosis, and Treatment

Blastomycosis is caused by Blastomyces dermatitidis/gilchristii, a dimorphic fungus endemic to the Ohio/Mississippi River valleys, Great Lakes, and southeastern U.S. Infection follows inhalation of conidia from disturbed soil or decaying wood.

Clinical Spectrum

• Asymptomatic/Subclinical: ~50% of infections; detected by serology/skin test.
• Acute Pulmonary: 1–3 weeks post-exposure; fever, cough, pleuritic pain, myalgias, fatigue. Mimics bacterial pneumonia.
• Chronic Pulmonary: Weeks to months; weight loss, night sweats, hemoptysis. Mimics TB/lung cancer.
• Disseminated: Hematogenous spread—skin (verrucous/ulcerative lesions), bone (osteomyelitis), GU (prostatitis, epididymitis), CNS (meningitis, brain abscess). Immunocompromised at higher risk.

Diagnosis

• Gold Standard: Culture (sputum, BAL, tissue, blood) — 2–4 weeks; biosafety level 3.
• Rapid: KOH prep/calcofluor white (broad-based budding yeast); antigen detection (MiraVista EIA — urine/serum/BAL, sensitivity ~90%); PCR (reference labs).
• Serology: Antibody (ID, CF) — supportive; cross-reacts with Histoplasma.
• Imaging: Patchy consolidations, nodules, mass-like lesions; not specific.

Treatment (IDSA Guidelines)

Severity	Regimen	Duration
Mild-Moderate Pulmonary	Itraconazole 200 mg TID × 3 days, then 200 mg BID	6–12 months
Severe/Disseminated/CNS	Liposomal Amphotericin B 3–5 mg/kg/day → step-down to itraconazole	≥12 months (CNS: lifelong suppression often)
CNS Involvement	Liposomal AmB + azole (itraconazole/voriconazole)	Extended; expert consult

• Monitor itraconazole levels (target 1–2 µg/mL); drug interactions (CYP3A4).
• Relapse ~10–20%; retreat with same/extended course.

Prevention

• Avoid soil disruption in endemic areas (excavation, construction, gardening).
• N95 if exposure unavoidable.
• No vaccine available.