Blastomycosis
Blastomycosis: Excerpt from The 5-Minute Pediatric Consult
Theoklis Zaoutis, MD
Blastomycosis - BASICS
Blastomycosis - description
- Systemic infection caused by the dimorphic soil fungus Blastomyces dermatitidis
- Dimorphism is characterized by a mold phase (mycelial form) that grows at room temperature and a yeast form that grows at body temperature.
- Incubation period estimated at 30–45 days
Blastomycosis - general prevention
- No special precautions for hospitalized patients are indicated.
- The natural reservoir is undetermined.
Blastomycosis - epidemiology
- Similar to other dimorphic fungi, B. dermatitidis is a soil saprophyte (mycelial form).
- No person-to-person transmission has been documented.
Blastomycosis - prevalence
- Infection is endemic in the US in the southeast and central states and in the towns bordering the Great Lakes, with the highest incidence in Arkansas, Kentucky, Louisiana, Mississippi, North Carolina, Tennessee, and Wisconsin.
- Other reported areas of infection include parts of Canada (Ontario, Manitoba), Africa, India, and South America.
- Disease may be more severe and chronic in children with T-cell defects (especially HIV infection).
- Children account for 3–11% of cases of blastomycosis.
Blastomycosis - pathophysiology
- Inhalation of the fungus into the lung is followed by an inflammatory response with neutrophils and macrophages.
- Blastomycosis most commonly presents as a subacute pulmonary disease, but the clinical spectrum of the disease extends from asymptomatic to disseminated disease that involves the skin, bones, and genitourinary system.
Blastomycosis - etiology
- Infection is most commonly caused by inhalation of spores from Blastomyces dermatitidis.
- Less common modes of acquiring the infection include accidental inoculation, dog bites, conjugal transmission, and intrauterine transmission.
- Point-source outbreaks have been associated with occupational and recreational activities that occur in areas with moist soil and decaying vegetation, such as along streams and rivers.
- Natural infection occurs only in 2 mammalian species, humans and dogs.
Blastomycosis - associated conditions
- Pulmonary blastomycosis:
- Most common form of infection by Blastomyces in children
- Can be acute, subacute, or chronic
- Illness severity can vary greatly, from asymptomatic to presentations of upper respiratory tract infection, bronchitis, pleuritis, pneumonia, or severe respiratory distress.
- Cutaneous blastomycosis:
- Skin manifestations are variable and include nodules, verrucous lesions, subcutaneous abscesses, or ulcerations.
- Cutaneous disease occurs following pulmonary inoculation in most cases, but can also occur after direction inoculation into the skin.
- Disseminated blastomycosis: Usually begins as pulmonary infection, with subsequent spread to involve skin (most commonly), bone, genitourinary tract, and CNS
Blastomycosis - DIAGNOSIS
Blastomycosis - signs & symptoms
Blastomycosis - history
- For children with acute pulmonary blastomycosis, the most common presenting symptoms are:
- Cough (may be productive)
- Fever
- Chest pain
- Malaise
- Children with chronic pulmonary disease present with:
- Chronic (>2 weeks) nonproductive cough
- Pleuritic chest pain
- Poor appetite
- May also be a history of fever, chills, weight loss, fatigue, night sweats, or, rarely, hemoptysis
- History of residence or travel to an endemic area
Blastomycosis - physical exam
- Initial pulmonary infection may present with physical examination findings similar to those of bacterial pneumonia.
- Respiratory signs and symptoms often have resolved by the time cutaneous manifestations are apparent.
- Skin involvement appears as nodules, nodules with ulceration, and finally, granulomatous lesions with advancing borders.
- Sites in disseminated disease include lung, skin, bone, genitourinary tract, CNS, and infrequently, liver and spleen, lymph nodes, thyroid, heart, adrenals, omentum, GI tract, muscles, and pancreas.
- Chest radiography commonly reveals consolidation of lobar consolidation. Cavitation, fibronodular patterns, and mass effect may also be seen.
Blastomycosis - tests
Blastomycosis - lab
- Definitive diagnosis requires the growth of B. dermatitidis from a clinical specimen.
- Direct visualization of the yeast form may be performed on samples of sputum, urine, cerebrospinal fluid, bronchoalveolar lavage sample, or tissue biopsy.
- Culture of the organism from samples can be performed and a DNA probe used to identify B. dermatitidis.
- Serologic tests lack sensitivity and specificity and are generally not helpful in establishing of blastomycosis.
- A negative serologic test does not rule out infection, and a positive test should not be used as an indication to start treatment with Blastomyces.
- The most accurate serologic test is the enzyme immunoassay.
Blastomycosis - differencial diagnosis
- Acute bacterial infection
- Neoplasm
- Tuberculosis
- Other fungal infections causing pneumonia
Blastomycosis - TREATMENT
Blastomycosis - medication
- Mild or moderate pulmonary disease:
- Oral itraconazole
- Alternative agents include ketoconazole or fluconazole.
- Severe pulmonary disease, CNS, or other severe infection:
- IV amphotericin B
- Therapy for some patients may be switched to oral itraconazole after clinical stabilization with amphotericin B.
- The use of lipid formulations of amphotericin B has not been reported for CNS blastomycosis, but this treatment may be an alternative for patients unable to tolerate amphotericin B.
- Length of therapy is site dependent:
- ≥6 months or longer for pulmonary disease
- ≥12 months or longer for bone disease
- Voriconazole, a new azole agent, and caspofungin, an echinocandin-class antifungal, have in vitro activity against B. dermatitidis.
Blastomycosis - FOLLOW UP
Blastomycosis - prognosis
- Before antifungal medications were available, the mortality associated with blastomycosis was up to 90%.
- Appropriate treatment with antifungal medications results in excellent cure rates and mortality rates of <10%.
- The prognosis for chronic cutaneous disease is better than that for systemic disease.
Blastomycosis - complications
- Dissemination is the main complication of the infection, occurring in up to 80% of children with blastomycosis.
- Systemic infection may be well advanced before symptoms are noted, making eradication more difficult. Long-term therapy and follow-up may be necessary.
Blastomycosis - bibliography
American Academy of Pediatrics. Blastomycosis. In: Pickering L, ed. 2006 Red Book: Report of the Committee on Infectious Diseases. 27th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2006:232–233.- Bradsher RW, Chapman SW, Pappas PG. Blastomycosis. Infect Dis Clin North Am. 2003;17:21–40, vii.
Chapman SW. Blastomyces dermatitis. In: Mondell GL, et al., eds. Principles and Practice of Infectious Diseases. 5th ed. New York: Churchill Livingstone; 2000:2733–2746.- Chapman SW, Bradsher RW, Campbell GD, Jr, et al. Practice guidelines for the management of patients with blastomycosis. Clin Infect Dis. 2000;30:679–683.
- Chu JH, Feudtner C, Heydon KH, et al. Hospitalizations for endemic mycoses: A population based national sample. Clin Infect Dis. 2006;42:822–825.
- Maxon S, Jacobs RF. Community-acquired fungal pneumonia in children. Semin Respir Infect. 1996;11:196–203.
Schutze G. Blastomycosis. In: Feigin RD, Cherry JD, eds. Textbook of Pediatric Infectious Diseases. 5th ed. Philadelphia: WB Saunders; 2004:2560–2568.- Varkey B. Blastomycosis in children. Semin Respir Infect. 1997;12:235–242.
Blastomycosis - CODES
Blastomycosis - icd9
116.0 Blastomycosis
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Book Source Details
- Book Title: The 5-Minute Pediatric Consult
- Author(s): M. William Schwartz MD; et al.
- Year of Publication: 2008
- Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: The 5-Minute Pediatric Consult
Authors: M. William Schwartz MD; et al.
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7577-9
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