• Blastomycosis is a chronic disease characterized by granulomatous and suppurative lesions.
• It may cause asymptomatic infection or be associated with acute, chronic, or rapidly progressive systemic disease.
• It causes a large number of different presenting symptoms and different radiographic appearances.

• Infection occurs after inhalation of conidia (spores of mycelial form).
• No person-to-person transmission
• Human infection is not uncommon. It is endemic in the United States in the southeast and central states and in the towns bordering the Great Lakes, with the highest incidence in the United States 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.
• Natural infection occurs only in two mammalian species: humans and dogs.
• It may be associated with immune compromise, but is not common in patients with HIV.
• Uncommon in the pediatric age group (<4% of cases in the most extensive patient review)
• Incubation period estimated at 30 to 45 days

• Dissemination is the main complication of the infection.
• Systemic infection may be well advanced before symptoms are noted, making eradication more difficult. Long-term therapy and follow-up may be necessary.

• Self-limited pulmonary infection is often undiagnosed and resolves without dissemination (almost 50% of those infected may be asymptomatic).
• Early treatment with amphotericin B in progressive, severe, or disseminated disease is effective, with excellent rates of cure.
• The prognosis for chronic cutaneous disease is better than that for systemic disease.
• The number of deaths from blastomycosis is decreasing with the use of antifungal agents. Prevalence of blastomycosis remains high, however, in endemic areas.

• 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 URI, 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 be inoculated primarily to skin.
• Disseminated blastomycosis: usually begins as pulmonary infection, with subsequent spread to involve skin (most commonly), bone, GU tract, and CNS.

• Tuberculosis
• Neoplasm
• Sarcoidosis
• Other bacterial, viral, and fungal infections causing URI, bronchitis, pleuritis, and pneumonia

• Symptoms of common respiratory infections (nonproductive cough, pleuritic chest pain, poor appetite) that last more than 2 weeks. There 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

• Initial pulmonary infection may present as a mild respiratory infection. 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, GU tract, CNS, and, infrequently, liver and spleen, lymph nodes, thyroid, heart, adrenals, omentum, GI tract, muscles, and pancreas.
• CXR indicated by physical examination or history may show localized consolidation in acute disease, and cavitations or pulmonary nodules with a more chronic course.

• Direct visualization of the yeast form may be performed on samples of sputum, urine, CSF, BAL sample, or tissue biopsy after 10% potassium hydroxide preparation.
• Culture of the organism from samples can be performed and a DNA probe used to identify B. dermatitidis.
• Serologic testing may be helpful in disseminated disease.
• Immunodiffusion testing is reliable for indication of infection, but a negative test does not rule out infection with Blastomyces.
• Severe pulmonary infection may develop with cavitation, pneumonia, or pulmonary nodules apparent on chest x-ray films.

• Mild or moderate disease is treated with oral itraconazole or ketoconazole, with or without an initial short course of amphotericin B.
• Severe or CNS or other severe infection should be treated with intravenous amphotericin B.
• Length of therapy is site-dependent: at least 6 months for pulmonary disease and at least 12 months for bone disease.

• INFECTION CONTROL
• No special precautions for hospitalized patients are indicated.
• Outbreaks have occurred, with clustering of cases occurring at the same place and time.
• A natural reservoir is undetermined.

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Chapman SW. Blastomyces dermatitis. In: Mandell GL, et al., eds. Principles and practice of infectious diseases, 3rd ed. New York: Churchill Livingstone, 1990:1999–2007.

Maxon S, Jacobs RF. Community-acquired fungal pneumonia in children. Semin Respir Infect 1996;11(3):196–203.

Mitchell TG. Blastomycosis. In: Feigin RD, Cherry JD, eds. Textbook of pediatric infectious diseases, 3rd ed. Philadelphia: WB Saunders, 1992:1898–1904.

Varkey B. Blastomycosis in children. Semin Respir Infect 1997;12(3):235-242.