Pediatric Blastomycosis Workup
- Author: Russell W Steele, MD; Chief Editor: Russell W Steele, MD more...
Laboratory Studies
The following studies are indicated in patients with blastomycosis:
Sputum examination
In general, sputum specimens processed with 10% potassium hydroxide or a fungal stain are examined first in adolescent and adult patients because specimens have a high overall yield (approximately 80%). In addition, cytologic specimens can be examined for a dependable diagnosis.
Culture
The diagnosis of blastomycosis can be made by growth of the fungus in a culture of sputum, tracheal aspirates, bronchoalveolar lavage fluid, tissue biopsy specimens, cerebrospinal fluid, or urine. Because colonization with B dermatitidis does not occur, detection of the fungus from any sterile site is diagnostic. The organism can be cultured on brain-heart infusion and Sabouraud dextrose agar at room temperature. In experienced hands, diagnosis of blastomycosis by visualization of the characteristic budding yeast formed in wet smear or histopathologic section is adequate.
Because primary cutaneous blastomycosis has been reported by accidental autoinoculation, clinical laboratory personnel and pathologists should be notified about the possibility of blastomycosis in the differential diagnosis when handling potential infected tissue or body fluid specimens.
Skin tests and serodiagnosis
Skin testing and serodiagnosis of blastomycosis using complement fixation (CF) antibodies and immunodiffusion (ID) precipitin bands currently have very limited roles in diagnosis because of poor sensitivity and specificity, with cross-reactivity of other fungi.
Recently developed enzyme immunoassay with the A-antigen of B dermatitidis has been shown to be more sensitive than CF and ID tests; however, this test has limited clinical use because it is not available in most commercial laboratories.
DNA
Chemiluminescent DNA probes are available for identification of B dermatitidis.
Imaging Studies
- Chest radiography: The chest radiograph is abnormal in two thirds of cases and may reveal alveolar or masslike infiltrates, reticulonodular pattern, pleural effusion, and, rarely, cavitation. See an example of findings in the image below.
Lateral chest radiograph reveals the ill-defined lingular opacity and an absence of pleural effusions. - Bone scanning: A radionuclide bone scan and other imaging modalities, such as CT scanning or even the more sensitive MRI, may help detect skeletal involvement in some cases of extrapulmonary blastomycosis.
Other Tests
- Skin biopsy: Blastomycosis can present with cutaneous lesions. In these situations, histology and culture on skin biopsy specimens may reveal the organism.
- Immune deficiency workup: In recent years, serious infection with blastomycosis is recognized increasingly in immunocompromised hosts, especially patients with AIDS. However, other fungal infections, such as progressive disseminated histoplasmosis or cryptococcal meningitis, are more likely to be opportunistic. Blastomycosis is not an AIDS-defining illness and no official recommendations regarding screening for human immunodeficiency virus (HIV) infection in patients diagnosed with blastomycosis are recognized.
- Lumbar puncture: Neurologic manifestations of blastomycosis include meningitis and, more commonly, epidural or cranial abscesses. Diagnosis is difficult, and evaluation of lumbar spinal fluid is rarely definitive. Ventricular fluid has been associated with higher rates of culture positivity.
Procedures
- The diagnosis of blastomycosis is more difficult in children. Children with pulmonary disease who are unable to produce sputum may require invasive procedures, such as bronchoscopy with bronchoalveolar lavage, percutaneous needle biopsy of lung, and open lung biopsy, for diagnostic confirmation.
Histologic Findings
- The definitive diagnosis of blastomycosis is based on identification of the characteristic thick-walled broad-based budding yeast cells in tissue specimens or growth of the fungus in culture.
- Pathologically, a pyogranulomatous tissue response including lymphocytes, giant cells, and neutrophils is observed with associated necrosis and fibrosis.
- Pseudoepitheliomatous hyperplasia may be striking and may lead to an erroneous diagnosis of squamous cell carcinoma.
- Typically, the granuloma of blastomycosis does not caseate or calcify as in tuberculosis.
Pappas PG, Pottage JC, Powderly WG, et al. Blastomycosis in patients with the acquired immunodeficiency syndrome. Ann Intern Med. May 15 1992;116(10):847-53. [Medline].
Meyer KC, McManus EJ, Maki DG. Overwhelming pulmonary blastomycosis associated with the adult respiratory distress syndrome. N Engl J Med. Oct 21 1993;329(17):1231-6. [Medline].
Schutze GE, Hickerson SL, Fortin EM, et al. Blastomycosis in children. Clin Infect Dis. Mar 1996;22(3):496-502. [Medline].
Klein BS, Vergeront JM, Weeks RJ, et al. Isolation of Blastomyces dermatitidis in soil associated with a large outbreak of blastomycosis in Wisconsin. N Engl J Med. Feb 27 1986;314(9):529-34. [Medline].
[Guideline] Chapman SW, Bradsher RW JR, Campbell GD Jr, et al. Practice guidelines for the management of patients with blastomycosis. Infectious Diseases Society of America. Clin Infect Dis. Apr 2000;30(4):679-83. [Medline].
Dismukes WE, Bradsher RW Jr, Cloud GC, et al. Itraconazole therapy for blastomycosis and histoplasmosis. NIAID Mycoses Study Group. Am J Med. Nov 1992;93(5):489-97. [Medline].
Dismukes WE, Cloud G, Bowles C. Treatment of blastomycosis and histoplasmosis with ketoconazole. Results of a prospective randomized clinical trial. National Institute of Allergy and Infectious Diseases Mycoses Study Group. Ann Intern Med. Dec 1985;103(6 ( Pt 1)):861-72. [Medline].
Pappas PG, Bradsher RW, Chapman SW, et al. Treatment of blastomycosis with fluconazole: a pilot study. The National Institute of Allergy and Infectious Diseases Mycoses Study Group. Clin Infect Dis. Feb 1995;20(2):267-71. [Medline].
Ta M, Flowers SA, Rogers PD. The role of voriconazole in the treatment of central nervous system blastomycosis. Ann Pharmacother. Oct 2009;43(10):1696-700. [Medline].
Chapman SW, Lin AC, Hendricks KA, et al. Endemic blastomycosis in Mississippi: epidemiological and clinical studies. Semin Respir Infect. Sep 1997;12(3):219-28. [Medline].
Panicker J, Walsh T, Kamani N. Recurrent central nervous system blastomycosis in an immunocompetent child treated successfully with sequential liposomal amphotericin B and voriconazole. Pediatr Infect Dis J. Apr 2006;25(4):377-9. [Medline].
Pappas PG, Threlkeld MG, Bedsole GD, et al. Blastomycosis in immunocompromised patients. Medicine (Baltimore). Sep 1993;72(5):311-25. [Medline].
Sarosi GA, Hammerman KJ, Tosh FE, Kronenberg RS. Clinical features of acute pulmonary blastomycosis. N Engl J Med. Mar 7 1974;290(10):540-3. [Medline].
Shetty AK, Quinonez JM, Steele RW. Fever, hemoptysis and pneumonia in a twelve-year-old girl. Pediatr Infect Dis J. Sep 1998;17(9):849; 852-3. [Medline].
Steele RW, Abernathy RS. Systemic blastomycosis in children. Pediatr Infect Dis. Jul-Aug 1983;2(4):304-7. [Medline].
Sugar AM, Picard M. Macrophage- and oxidant-mediated inhibition of the ability of live Blastomyces dermatitidis conidia to transform to the pathogenic yeast phase: implications for the pathogenesis of dimorphic fungal infections. J Infect Dis. Feb 1991;163(2):371-5. [Medline].
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