Fungus

Blastomycosis

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Blastomycosis, Blastomyces dermatidis

  • See Also
  1. Cutaneous Blastomycosis
  2. Fungal Lung Infection
  • Pathophysiology
  1. Caused by Blastomyces dermatidis (dimorphic fungus)
  2. Transmitted by exposure to contaminated soil or decomposing timber
    1. Inhalation of spores
    2. Traumatized, non-intact skin exposure (see Cutaneous Blastomycosis)
  3. Endemic regions of United States (surrounding large water bodies)
    1. Ohio River Basin
    2. Mississippi River Basin
    3. Great Lakes
    4. St. Lawrence River
  • Symptoms
  1. Pulmonary involvement is initially asymptomatic in 50% of cases
  2. Symptomatic patients have similar presentations to viral and Bacterial Pneumonia (but more insidious)
    1. Fever
    2. Sweating
    3. Cough
    4. Dyspnea
    5. Chest Pain (may be Pleuritic Chest Pain)
    6. Weight loss
    7. Nocturnal Joint Pain
  • Signs
  1. Acute disease
    1. Self-limited Pneumonia may clear spontaneously in most patients
    2. Skin involvement (most common extrapulmonary manifestation of Blastomycosis)
      1. See Cutaneous Blastomycosis
  2. Disseminated blastomyces lesions from hematogenous spread (severe cases may be fatal)
    1. Bone
    2. Genitourinary system (including Kidneys)
    3. Nervous system
    4. Liver
    5. Spleen
  • Imaging
  1. Chest XRay of Chronic Blastomycosis
    1. Test Sensitivity: 66%
    2. Osteolytic lesions
    3. Pleural Effusions
  • Lab
  1. Microscopy
    1. Broad-based budding
  2. Skin lesion Evaluation
    1. Pustular discharge for Potassium Hydroxide
    2. Skin biopsy
    3. See Cutaneous Blastomycosis
  3. Systemic disease
    1. Bone Marrow Aspirate
    2. Sputum
  • Management
  1. Progressive, refractory, or severe disease or Central Nervous System involvement
    1. Amphotericin B 0.5-0.6 mg/kg (max 2.0 - 2.5 g) daily until stable
    2. After Amphotericin B IV course, transition to oral Itraconazole for 12 months
  2. Indolent disease (mild to moderate cases)
    1. Adults: Itraconazole 200 mg orally daily for 6 months
    2. Children and Pregnant women: Amphotericin B at dosing above
  • Course
  1. Incubation: 30-45 days
  • References
  1. Altman (2007) Am Fam Physician 76:1533-4 [PubMed]
  2. Bradsher (2003) Infect Dis Clin North Am 17:21-40 [PubMed]
  3. Gruber (2024) Am Fam Physician 109(5): 467-8 [PubMed]