Acute pulmonary histoplasmosis is a respiratory infection caused by inhaling the spores of the fungus Histoplasma capsulatum.

Histoplasma capsulatum, the fungus that causes histoplasmosis, is found in the Central and Eastern United States, Eastern Canada, Mexico, Central America, South America, Africa, and Southeast Asia. It is is commonly found in the soil along river valleys. It gets into the soil mostly from bird and bat droppings.

You can get sick when you breathe in spores produced by the fungus. Every year, thousands of people worldwide are infected, but do not become seriously sick. Most patients have no symptoms or have only a mild flu-like illness and recover.

Acute pulmonary histoplasmosis may happen as an epidemic, with many people in a particular geographical area becoming sick at the same time. Ongoing disease that continues to get worse can happen in people with impaired immune systems, such as those with HIV.

Risk factors include traveling to or living in the Central or Eastern United States near the Ohio and Mississippi River Valleys, and being exposed to the droppings of birds and bats. This threat is greatest after an old building is torn down, or when exploring caves. Having a weakened immune system increases your risk for getting the disease, and for having more and worse symptoms.

Most people with histoplasmosis have only very mild symptoms. The most common ones are:

• Chest pain
• Chills
• Cough
• Fever
• Joint pain and stiffness
• Muscle aches and stiffness
• Rash
• Shortness of breath

In the very young, elderly, or immunocompromised people, symptoms may be more severe. They include serious lung infections, severe joint pains, and inflammation around the heart.

A common test to diagnose histoplasmosis is checking for histoplasmosis antigen in the urine. This test is especially useful in patients with severe disease.

Other tests that may be done include:

• Antibody tests for histoplasmosis (also called serologies)
• Biopsy of site of infection
• Bronchoscopy (usually only done if symptoms are severe or if you have an abnormal immune system)
• Complete blood count (CBC)
• Chest CT scan
• Chest x-ray (might show a lung infection or pneumonia)
• Sputum culture (often not positive, even if you are infected)

Most cases of histoplasmosis clear up on their own. No treatment is needed beyond bedrest and medication to control fever.

If you are sick for more than 1 month or are having breathing problems, your doctor may prescribe medication. Drugs used to treat this condition include Itraconazole and Amphotericin B.

When histoplasmosis infection is severe and progressive, the illness may last for 1 to 6 months. Even then, it is rarely fatal. It can be a very serious illness in people with weak immune systems, such as those who have had bone marrow or solid organ transplants, those who have AIDS, or those who take medications to suppress their immune system.

Histoplasmosis can spread to other organs through the bloodstream (dissemination). This is usually seen in infants, young children, and immunosuppressed patients.

Acute histoplasmosis can get progressively worse or can become chronic histoplasmosis (doesn't go away).

Call your health care provider if you have symptoms of histoplasmosis, especially if you have an immune disorder, have been recently exposed to bird or bat droppings, or if you are being treated for histoplasmosis and new symptoms develop.

Avoid contact with bird or bat droppings if you are in an area where the spore is coommon, especially if you have a weakened immune system.

Kauffman CA. Histoplasmosis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, PA: Saunders Elsevier; 2007: chap 353.

Waht LJ, Freifeld AG, Kleiman MB, et al. Clinical practice guildelines for the management of patients with histoplasmosis: 2007 update by the Infectious Diseases Society of America. Clin Infect Dis. 2007;45(7):807-25.