Histoplasmosis - chronic pulmonary

Definition

Chronic pulmonary histoplasmosis is a respiratory infection caused by the fungus Histoplasma capsulatum.

Causes, incidence, and risk factors

Histoplasma capsulatum is a fungus found in the soil of the central and eastern United States (especially Mississippi and Ohio river valleys), eastern Canada, Mexico, Central America, and South America.

The infection occurs when a person breaths in the reproducing parts of the fungus, called spores. Those with healthy immune systems usually do not have symptoms, or only mild ones. This "acute" infection does not persist.

However, the infection can linger in those with lung problems such as smokers with emphysema or chronic obstructive pulmonary disease ( COPD). This condition is called "chronic" pulmonary histoplasmosis. The symptoms and chest x-ray findings of chronic pulmonary histoplasmosis are similar to tuberculosis.

Risk factors for chronic pulmonary histoplasmosis include:

• Living in or traveling to central or eastern United States
• Exposure to soil or particles contaminated with droppings of chickens, bats, or blackbirds
• Pre-existing COPD
• Weakened immune systems such as in people who have AIDS

Symptoms

• Fever
• Chills
• Unintentional weight loss
• Cough that brings up mucus or pus
• Shortness of breath
• Joint stiffness
• Skin involvement (erythema nodosum)

Signs and tests

Tests that may be used in the diagnosis of chronic pulmonary histoplasmosis include:

• Chest x-ray
• Chest CT scan
• Sputum culture and stain
• Biopsy of infected tissue such as open lung biopsy  or bone marrow biopsy
• Bronchoscopy with transbronchial biopsy or bronchoalveolar lavage
• Histoplasma complement fixation titer
• Histoplasma urinary antigen test
• Immunodiffusion test for precipitating antibodies to antigens of histoplasma
• CBC

Treatment

Antifungal medications are prescribed to control the infection within the lung. Itraconazole (by mouth) or amphotericin B (intravenously) is usually successful.

Expectations (prognosis)

The infection usually goes away with antifungal medication, but scarring inside the lung often remains. Many patients will still be sick due to their pre-existing lung disease.

Often times, those who have had chronic pulmonary histoplasmosis must follow up with their doctor, who will check for signs of relapse.  

In rare cases, a pulmonary histoplasmosis infection can spread through the blood to other organs. This is called disseminated histoplasmosis. People who have suppressed immune systems and very young children are more likely to develop this condition. If this occurs, the prognosis is less favorable.

Complications

• Disseminated histoplasmosis
• Respiratory insufficiency
• Lung scarring (fibrosis)
• Pericarditis
• Arthritis

Calling your health care provider

Call for an appointment with your health care provider if symptoms of chronic pulmonary histoplasmosis develop.

Call your health care provider if symptoms continue despite treatment, or if breathing difficulty or symptoms of disseminated histoplasmosis occur.

Prevention

Avoiding travel to areas where Histoplasma capsulatum is found would prevent exposure, but this may not be practical.

Avoid bird or bat droppings if you are in one of these areas, especially if you are immunosuppressed.

Illustrations

Coccidioidomycosis - chest X-ray

Fungus

Page Content:

Chronic cavitary histoplasmosis