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)
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.
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.
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.
Review Date:
5/25/2010
Reviewed By:
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
