Histoplasmosis

Background

Histoplasmosis after return from Pennsylvania, United States

• Fungal infection caused by Histoplasma capsulatum
• Endemic to the Ohio, Missouri, and Mississippi River valleys in the United States
• Exposure from disruption of soil containing organisms leads to aerosolization
• Activities associated with high-level exposure include spelunking, excavation, and demolition of old buildings

Clinical Features

• Disease manifestation depends on intensity of exposure, immune status, and underlying lung architecture

Acute Pulmonary Histoplasmosis

• 90% asymptomatic, and usually self-limited
• Symptoms 1-4 weeks after exposure and consist of flu-like illness
  • Fever/chills
  • Headache
  • Malaise
  • Myalgias
  • Abdominal pain
  • Arthralgias
  • Dyspnea
  • Cough, hemoptysis
• Hilar/mediastinal lymphadenopathy on CXR

Chronic Pulmonary Histoplasmosis

• Mostly older patients or smokers with underlying structural lung disease
• Symptoms:
  • Cough
  • Weight loss
  • Low-grade fever
  • Malaise
  • Night sweats
  • Sometimes hemoptysis, sputum production, dyspnea
• CXR may show:
  • Upper lobe infiltrates
  • Fibrosis, scarring
  • Cavitations

Progressive Disseminated Histoplasmosis

• Seen in immunocompromised patients
• SIRS
• Acute form:
  • Diffuse interstitial or reticulonodular lung infiltrates
  • Respiratory failure
  • Coagulopathy
  • Multiorgan failure
• Subacute form depends on focal organ system affected:
  • Fever
  • Weight loss
  • Hepatosplenomegaly
  • Meningitis, brain lesions
  • Mucosal or GI ulcerations
  • Adrenal insufficiency
  • Pericarditis
• Chronic form: constitutional sx

Mediastinitis

• Enlarged lymph nodes that may undergo necrosis
• This leads to granulomatous mediastinitis
• Can lead to:
  • Superior vena cava syndrome
  • Obstruction of pulmonary vessels
  • Airway obstruction
  • Recurrent pneumonia
  • Hemoptysis
  • Respiratory failure

Differential Diagnosis

• Aspergillosis
• Blastomycosis
• Carcinoid Lung Tumors
• Chlamydophila psittaci
• Coccidioidomycosis
• Legionella pneumonias
• Lung Cancer, Small Cell
• Lymphoma, Mediastinal
• Mediastinal Cysts
• Lung Abscess
• Mycoplasma Infections
• Pancoast Syndrome
• Pneumococcal Infections
• Pneumocystis Carinii Pneumonia
• Aspiration Pneumonia
• Pneumonia
• Sarcoidosis
• Tuberculosis

Workup

• CXR
  • Normal in 40-70% of cases
  • Pneumonitis with hilar adenopathy
  • Focal pulmonary infiltrates with light exposure
  • Diffuse infiltrates with heavy exposure
• CBC (mild anemia in chronic disease)
• Alkaline phosphatase (elevated in disseminated and chronic disease)
• LDH (elevated in AIDS patients with disseminated disease)
• Definitive diagnosis by:
  • Sputum cultures
  • Blood cultures
  • Antibody testing
  • Serum/urine antigen testing
• Further imaging if concerned for specific organ involvement in disseminated disease (head CT, abdominal CT or lumbar puncture)

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