Lung Infection, Histoplasmosis

• • Infection occurs after inhalation of spores with male:female ratio of 3:1

  • In lungs, fungus germinates into yeast; cause caseating necrosis and calcification

Acute Infection

• • Several different presentations:

  • -Flu-like syndrome

    -Flu-like syndrome but limited to lungs

    -Diffuse nodular disease

Chronic Infection

• • Several presentations:

  • -Asymptomatic solitary nodule < 3 cm with central calcifications in lower lobes (histoplasmoma)

    -In patients with chronic obstructive pulmonary disease, cavitary histoplasmosis 3

    -Mediastinal granulomas resulting in broncholithiasis, esophageal traction diverticula, superior vena cava (SVC) compression, transesophageal (TE) fistulas

    -Fibrosing mediastinitis with SVC, tracheal, or esophageal compression

Epidemiology

• • Pulmonary fungal infections are rising due to widespread use of broad-spectrum antibiotics, immunosuppressive drugs, and HIV infection

  • Occur anywhere in world, some with characteristic endemic areas

  • Histoplasma capsulatum is found in fowl and bat excreta, pigeon roosts, chicken houses, caves, hollow trees, attics and lofts

  • -Endemic to fertile river valleys, such as Mississippi, Missouri, and Ohio Rivers

Symptoms and Signs

• • Immunocompetent patients, asymptomatic

  • Cough, malaise, hemoptysis, fever, weight loss (30% have coexistent TB)

Acute Infection

• • Ranging from flu-like illness to diffuse nodular disease

Chronic Infection

• • Variety of presentations:

  • -Histoplasmoma most common

    -Local mediastinal compression can occur

  • Disseminated disease (acute, subacute, and chronic form): Fever, abdominal pain, hepatosplenomegaly, pancytopenia

  • Solitary pulmonary nodules: 15-20% are from histoplasmosis

  • Constrictive pericarditis if pericardium involved

Laboratory Findings

• • High or rising serum titers

  • Tissue cultures, sputum cultures

Imaging Findings

• • Chest film: Hilar adenopathy common, diffuse interstitial pneumonitis (25%)

  • In acute presentation, chest film ranges from upper lobe opacities to diffuse 3-4 mm nodules

  • Cavitation indicates advanced disease

• • High/rising serum titers (> 1:32 or elevated 4×)

  • Histoplasmin skin test (positive in 2-6 wks)

  • Sputum cultures positive in 10%, tissue cultures more reliable

Rule Out

• • TB

• • Chest x-ray

  • Chest CT scan

  • Sputum microscopy and cultures

• • Medical therapy is indicated in immunocompromised hosts or in cavitary or severe disease

Surgery

• • Operative therapy only for complications:

  • -Broncholithectomy + pulmonary resection

    -Repair of TE fistula

    -Decompression of mediastinal granulomas

    -Saphenous vein bypass for severe SVC compression

Indications

• • Complications of histoplasmosis

Medications

• • Ketoconazole/itraconazole (6 mos) for cavitary disease

  • Amphotericin B for more serious infections or in immunocompromised patients

References