Histoplasmosis is an infection that occurs from breathing in the spores of the fungus Histoplasma capsulatum.
Ohio River Valley fever; Fibrosing mediastinitis
Causes, incidence, and risk factors
Histoplasmosis is a fungal infection. It occurs throughout the world. In the United States, it is most common in the southeastern, mid-Atlantic, and central states.
Histoplasma fungus grows as a mold in the soil. You can get sick when you breathe in spores produced by the fungus. Soil that contains bird or bat droppings may have larger amounts of this fungus. The threat is greatest after an old building is torn down or in caves.
Having a weakened immune system increases your risk for getting or reactivating this disease. Very young or very old people, or those with AIDS, cancer, or an organ transplant have more severe symptoms.
People with chronic lung disease (such as emphysema and bronchiectasis) are at higher risk of a more severe infection.
Most people have no symptoms, or only have a mild flu-like illness.
The infection may be active for a short period of time, and then the symptoms go away. Sometimes, the lung infection may become long-term (chronic). Symptoms include:
Chest pain and shortness of breath
Cough, possibly coughing up blood
Fever and sweating
In a small number of patients, histoplasmosis may spread throughout the body. These symptoms are not due to the infection, but instead are due to irritation and swelling (inflammation) in response to the infection. Symptoms may include:
Chest pain from swelling in the lining around the heart
Headache and neck stiffness from swelling in the covering of the brain and spinal cord
Signs and tests
Histoplasmosis is diagnosed by:
Biopsy of the lung, skin, liver, or bone marrow
Blood or urine tests to detect histoplasmosis proteins or antibodies
Cultures of the blood, urine, or sputum (this test provides the clearest diagnosis of histoplasmosis, but results can take 6 weeks)
To help diagnose this condition, your doctor may perform:
Spinal tap to look for signs of infection in cerbrospinal fluid (CSF)
Most of the time, histoplasmosis clears up without treatment. Resting and taking medication can control a fever.
If you are sick for more than 1 month or are having trouble breathing, your doctor may prescribe medication. The main treatment for histoplasmosis is antifungal drugs. Amphotericin B, itraconazole, and ketoconazole are the usual treatments.
Antifungals may need to be given through a vein, depending on the form or stage of disease.
Some of these medicines can have side effects.
Sometimes, long-term treatment with antifungal drugs may be needed. You may need to take these medications for up to 1 to 2 years.
The outlook depends on how severe the infection is, and the patient's health. Some people get better without treatment. An active infection will usually go away with antifungal medicine, but there may be scarring left inside the lung.
The death rate is higher for people with untreated widespread (disseminated) histoplasmosis whose immune system is not working well.
Scarring in the chest cavity may trap:
The major blood vessels carrying blood to and from the heart
The heart itself
The esophagus (food pipe)
The lymph nodes
Enlarged lymph nodes in the chest (called mediastinal granulomas) may press on body parts such as the esophagus and blood vessels of the lungs.
Calling your health care provider
Call your health care provider if you live in an area where histoplasmosis is common, and you develop flu-like symptoms, chest pain, cough, and shortness of breath. While there are many other illnesses that have similar symptoms, you may need to be tested for histoplasmosis.
Histoplasmosis may be prevented by reducing exposure to dust in chicken coops, bat caves, and other high-risk locations. Wear masks and other protective equipment if you work in these environments.
Kauffman CA. Histoplasmosis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011: chap 340.
Jatin M. Vyas, MD, PhD, Instructor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.