Histoplasmosis

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Background

  • Fungal infection caused by Histoplasma capsulatum
  • Endemic to the Ohio, Missouri, and Mississippi River valleys in the United States

Clinical Features

Acute Pulmonary Histoplasmosis

  • 90% asymptomatic, and usually self-limited
  • Fever/chills
  • Headache
  • Malaise
  • Myalgias
  • Abdominal pain
  • Joint pains
  • Dyspnea
  • Cough
  • Hemoptysis
  • Hilar/mediastinal lymphadenopathy

Chronic Pulmonary Histoplasmosis

  • Mostly older patients with underlying lung disease
  • Cough
  • Weight loss
  • Fever
  • Malaise
  • Sometimes hemoptysis, sputum production, dyspnea
  • CXR may show:
    • Upper lobe infiltrates
    • Fibrosis, scarring
    • Cavitations

Progressive Disseminated Histoplasmosis

  • Seen in immunocompromised patients
  • Acute form: fever, cough, weight loss, malaise, dyspnea, +/-CNS involvement
  • Subacute form: wide variety of symptoms depending on affected organ system
  • Chronic form: constitutional sx

Mediastinitis

  • Enlarged lymph nodes undergo necrosis
  • This leads to granulomatous mediastinitis

Differential Diagnosis

  • Aspergillosis
  • Blastomycosis
  • Carcinoid Lung Tumors
  • Chlamydial Pneumonias
  • Coccidioidomycosis
  • Legionella pneumonias
  • Lung Cancer, Small Cell
  • Lymphoma, Mediastinal
  • Mediastinal Cysts
  • Mycoplasma Infections
  • Pancoast Syndrome
  • Pneumococcal Infections
  • Pneumocystis Carinii Pneumonia
  • Pneumonia, Aspiration
  • Pneumonia, Bacterial
  • Pneumonia, Fungal
  • Pneumonia, Viral
  • Sarcoidosis
  • Tuberculosis

Workup

  • CBC (mild anemia in chronic disease)
  • Alkaline phosphatase (elevated in disseminated and chronic disease)
  • LDH (elevated in AIDS patients with disseminated disease)
  • Sputum cultures
  • Blood cultures
  • Antibody testing
  • Serum/urine antigen testing
  • CXR
  • Further imaging if concerned for specific organ involvement in disseminated disease (head CT, abdominal CT)

Treatment

Acute Pulmonary Histoplasmosis

  • Do not treat if asymptomatic
  • Itraconazole x 6-12 weeks
  • Severe disease: Amphotericin B x 1 week then Itraconazole x 1 year

Chronic Pulmonary Histoplasmosis

  • Itraconazole x 1 year

Progressive Disseminated Histoplasmosis

  • See above medical therapy
  • Surgical intervention may be needed for some end organ involvement

Sources

emedicine medscape