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Histoplasmosis - acute (primary) pulmonary

Definition

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

Causes, incidence, and risk factors

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 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 without any treatment.

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

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 or reactivating the disease, and for having more and worse symptoms.

Symptoms

Most people with acute pulmonary histoplasmosis have no or mild symptoms. The most common symptoms are:

• Chest pain
• Chills
• Cough
• Fever
• Joint pain and stiffness
• Muscle aches and stiffness
• Rash (usually small sores on the lower legs called erythema nodosum)
• Shortness of breath

In the very young, elderly, or people with a compromised immune system, symptoms may be more severe, including:

• Inflammation around the heart (called pericarditis)
• Serious lung infections
• Severe joint pain

Signs and tests

To diagnose histoplasmosis, the doctor needs to find the fungus in the body, or evidence that your immune system is reacting to the fungus.

Tests include:

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

Treatment

Most cases of histoplasmosis clear up without specific treatment. Patients are advised to rest and take 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.

Support Groups

Expectations (prognosis)

When histoplasmosis infection is severe or gets worse, the illness may last for 1 to 6 months. Even then, it is rarely fatal.

It can be a serious illness in people with weak immune systems, such as those who:

• Have AIDS
• Have had bone marrow or solid organ transplants
• Take medications to suppress their immune system

Complications

Acute pulmonary histoplasmosis can get worse over time, or can become chronic pulmonary histoplasmosis (which doesn't go away).

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

Calling your health care provider

Call your health care provider if:

• You have symptoms of histoplasmosis, especially if you have a weakened immune system or have been recently exposed to bird or bat droppings
• You are being treated for histoplasmosis and develop new symptoms

Prevention

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

References

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 guidelines for the management of patients with histoplasmosis: 2007 update by the Infectious Diseases Society of America. Clin Infect Dis. 2007;45(7):807-825.