Blastomycosis

By Matthew C. Hall, MD, Infectious Medicine Department, Marshfield Clinic

Your first patient of the day is 15-year-old being treated for pneumonia for the past week. He is not showing any improvement.

You take care of the whole family, but are unsure when you saw him last, since he has generally been healthy and is without any chronic medical conditions. The day sheet notes he was started on levofloxacin six days ago after being seen in walk-in clinic. You find a CXR from that visit that clearly has a right middle lobe infiltrate. He tells you about daily fevers, and becoming fatigued to the point of not being able to attend school.

After seeing the patient, you ask the medical student from Miami who is shadowing you this week, for her diagnostic differential for treatment failure of community acquired pneumonia (CAP). She comes up with thoughts on resistance bacteria, development of an empyema, or states the patient isn’t as healthy as he seems. This provides you with the perfect teaching moment on endemic mycoses.

Wisconsin is home to blastomycosis, and to a much lesser degree histoplasmosis. Infrequently we get to see coccidioidomycosis in someone who has traveled to or is visiting from the Southwest. In your 90-second teaching moment you explain the following to the student:

• In Wisconsin, blastomycosis is in the differential as a cause for pneumonia.
• Suspicion for blastomycosis is increased when epidemiology factors suggest an increased likelihood of exposure and specifically in cases of failing adequate treatment of a community acquired pneumonia.
• The initial diagnostic work-up is straightforward and uncomplicated with a simple fungal smear of expectorated sputum being the starting point.
• A blastomyces antigen test is now available, and provides an additional option with acceptable samples to include urine, blood, or bronchoscopy specimen (though results take 3 to 4 days as this test is sent out).
• The work-up gets more complicated when sputum is not available and a bronchoscopy procedure is needed to obtain adequate specimen.
• It is always helpful to notify the laboratory when you are trying to diagnose blastomycosis.
• Unfortunately, negative fungal smears or a blastomyces antigen test do not rule blastomycosis.
• Fungal cultures can be positive when smears are negative but this can delay the diagnosis.
• In situations where the likelihood of blastomycosis is high, repeat smears can be sent especially if better sputum samples are produced and the antigen test can also be repeated after a few days.
• Blastomycosis should also be considered in the differential for lung nodules, skin lesions, and osteomyelitis.
• Blastomycosis cannot be treated empirically with the treatment being too long and with excessive risk that limits doing this (exception being the presentation of the miliary pattern of disease with respiratory failure in which treatment is started awaiting confirmation).
• The patient is able to provide a sputum sample which on fungal smear is positive for blastomyces, completing the teaching moment.