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Key Features

Essentials of Diagnosis

  • Residence in, or travel to, an endemic area

  • In immunocompetent patients, most often a self-limited flu-like illness; acute pneumonia occurs in a minority of cases

  • Diagnosis by culture of specimens from bronchoscopy, skin, or other tissue, or antigen detection

General Considerations

  • Blastomyces dermatitidis is causative fungus

  • Found in soil primarily in the Mississippi and Ohio River valleys, additional southeastern and south central states, and the states bordering the Great Lakes

  • Transmission is by inhalation of spores

  • Subclinical disease is common

  • Infection rates are similar in both sexes

Clinical Findings

Symptoms and Signs

  • Primary infection is often unrecognized or associated with

    • Cough with purulent sputum

    • Chest pain

    • Headache

    • Weight loss

    • Night sweats

    • Fever

  • Infection is most often self-limited in immunocompetent patients

  • However, an indolent progressive pulmonary disease occurs after an incubation period of 20–100 (median 45) days in some patients

  • Cutaneous lesions

    • Usually represent disseminated disease

    • Slowly progressive

    • Ulcerative with a sharp, heaped-up border or verrucous appearance

  • Bone disease resembles other forms of chronic osteomyelitis

  • Lytic skull lesions in children are typical, but long bones, vertebrae, and the pelvis may be involved

  • Extrapulmonary disease occurs in 25–40% of patients with progressive disease

Differential Diagnosis

  • Acute viral, bacterial, or mycoplasmal infections

  • Tuberculosis

  • Histoplasmosis

  • Coccidioidomycosis

  • Cancer


Laboratory Findings

  • An initial suppurative response is followed by an increase in mononuclear cells and subsequent formation of noncaseating granulomas

  • Diagnosis requires isolation or visualization of the fungus

  • Pulmonary specimens (sputum, tracheal aspirates, or lung biopsy) may be positive using conventional or fungal cell wall stains

  • Budding yeasts have refractile thick walls and are very large and distinctive (figure-of-eight appearance)

  • Sputum specimens are positive in more than 80% of cases and in almost all bronchial washings

  • Skin lesions are positive in 80–100%

  • An ELISA antigen detection method

    • Readily detects Blastomyces antigen in serum, urine, and lung lavage fluids

    • There is cross-reactivity with histoplasmosis


  • Radiographic lobar consolidation and fibronodular interstitial and alveolar infiltrates are typical in cases with progressive pneumonia; effusions, hilar nodes, and cavities are less common

  • Miliary patterns also occur with acute infection

  • Cavities and fibronodular infiltration

    • Can develop in the upper lobes in patients with chronic disease similar to those seen in tuberculosis

    • However, these lesions rarely caseate or calcify


  • For CNS infection or moderately severe or life-threatening blastomycosis (especially if immunocompromised),

    • Lipid formulation of amphotericin B (3–5 mg/kg intravenously) for 1–2 weeks or until improved

    • Followed by oral itraconazole (5–10 mg/kg/d; divided into two doses) for 6 months

  • Mild to moderate blastomycosis is often treated with oral itraconazole alone for 6–12 months

  • Bone disease may ...

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