Infectious Agents
Case 2

Clinical Features
Light Microsocopy
Electron Microscopy
Discussion

Case 1
Case 2
Case 3
Case 4

Electron Microscopy of Infectious Agents

Case 2: Solitary Intracranial Blastomycotic Abscess

Discussion

Blastomycosis is an uncommon disease in humans that presents with CNS

involvement only in about 4-10% of cases, and the involvement usually consists of meningitis or multiple abscesses (1). A solitary intracranial abscess due to Blastomyces without systemic disease is an unusual manifestation (12 reported cases) that is difficult to diagnosis without tissue examination, and accurate diagnosis is essential because the entity is uniformly fatal without therapy (2).

Blastomycosis in humans is not common, and CNS involvement without multiple abscesses is rare. Once the organism was identified in the lesion, the patient was reexamined for other blastomycotic lesions, but none were found, which reaffirmed a solitary intracranial infection at presentation. A more thorough investigation of the clinical history confirmed that the patient had no chronic granulomatous disease, malignancy or acquired immunodeficiency, and had not received an organ transplant or immunosuppresive therapy. However, a neighbor's dog had died from pulmonary blastomycosis a few months prior to onset of the patient's symptoms, which is significant because the area in which the patient lived had been identified as one in which the disease had been contracted, and the close proximity to an infected dog may have provided an opportunity for the patient to contract the disease.

The role for electron microscopy in this case was to clarify the identity of the organism prior to completion of cultures, confirmation by complement fixation and double immunodiffusion tests of the patient's serum, and immunofluorescent staining of the materials by the Centers for Disease Control. An unexpected bonus was finding the budding yeast form.

References

1. Bell, R.M., Starshak, R.J., Sty, J.R., and Harb, J.M.: Solitary intracranial blastomycotic abscess. Wisconsin Medical Journal, 82(2): 23-25, 1983.
2. Fetter, B.F., Klintworth, G.K., and Hendry, W.S.: Mycoses of the Central Nervous System. Baltimore, The Williams & Wilkins Company, 1967, pp 38-52.
3. Tang, T.T., Marsik, F.J., Harb, J.M., et al.: Cerebral blastomycosis: an immunodiagnostic study. Am. J. Clin. Pathol. 82: 243-246, 1984.

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