Blastomyces dermatitidis is a dimorphic fungus found in Canada, the
United States and many other countries.
Inhaled fungal spores can infect the lungs and spread to other parts of the body. Blastomycosis
is one fungus that grows inside the body in yeast form. These yeast cells can
cause severe, invasive infection that is sometimes fatal because the diagnosis
is not made and effective treatment is not prescribed. The yeast cells spread
like cancer cells through the blood stream and can grow in every body tissue.
Infection by blastomyces is difficult to recognize even in areas
where physicians are aware of this problem. Infection usually begins in the
respiratory tract. The illness resembles influenza or pneumonia. Acute
blastomycosis is often misdiagnosed as bacterial pneumonia and is treated with
antibiotics with no benefit. Lung lesions that resemble tuberculosis or cancer
may appear and lead to further misdiagnosis and inappropriate treatment. Lesions
in the trachea and larynx are nodular and may be diagnosed as squamous cell
carcinoma unless a biopsy is performed and interpreted correctly.
Blastomycosis can spread to any tissue of the body.
In an area, where blastomycosis was known, only 18% of 123 patients at the
University of Mississippi Medical Center (Jackson, MS) were correctly
diagnosed at the initial patient evaluation. Pneumonia (40%), malignant tumors
(16%) and tuberculosis (14%) were the most common misdiagnoses. The false first
impression frequently resulted in unnecessary surgeries or treatment delays,
with patients receiving inefficient antibiotic therapy sometimes for months.
Sometimes the diagnosis was made in the autopsy room.
Adapted from The US CDC Description of Blastomycosis
Clinical Features Infection presents as a flu-like illness with fever, chest
pain, cough, aching, fatigue, weight loss. Some patients fail to recover and
develop chronic pulmonary infection or widespread disseminated infection
(affecting the skin, bones, and genitourinary tract). Occasionally, the brain
becomes infected. Infection can lead to permanent lung damage with chronic disease.
Transmission Inhalation of airborne spores after disturbance of
Risk Groups Persons in areas with with exposures to wooded, lakes,
rivers, beaver dams and construction sites (e.g., farmers, construction and
forestry workers, hunters, hikers and campers).
A standard recommendation for quick diagnosis is sputum microscopy -- a
simple and inexpensive test that in experienced hands can permit quick diagnosis
patients with a pneumonic presentation. The technique is to place a sample of freshly
expectorated sputum on a slide and digest it with drops of potassium hydroxide.
Cover it with a cover slip and examine it under a microscope. A standard
textbook describes yeasts, 8-20
micrometers in size, with single, broad-based buds, double refractile walls, and
multiple nuclei. I discovered that sputum containing this organisms had white
clumps and strings that contained yeast cells. The size variation was much
greater than the textbooks describe and that yeast cells transform within hours
of cooling and disappear in 24 - 48 hours. Specimens transported to a lab were
never properly handled and the diagnosis was never made by inexperienced
I diagnosed my own infection by sputum microscopy and developed a
2-slide culture method, described in this report.