Histoplasmosis

Definition

Histoplasmosis is an infection due to the Histoplasma capsulatum fungus.

Alternative Names

Ohio River Valley fever

Causes

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.

The infection enters the body through the lungs. Histoplasma fungus grows as a mold in the soil, and infection results from breathing in airborne particles. Soil contaminated with bird or bat droppings may have a higher concentration of histoplasma.

There may be a short period of active infection, or it can become chronic and spread throughout the body.

Histoplasmosis may have no symptoms. Most people who do develop symptoms will have a flu-like syndrome and lung (pulmonary) complaints related to pneumonia or other lung involvement. Those with chronic lung disease (such as emphysema and bronchiectasis) are at higher risk of a more severe infection.

About 10% of people with histoplasmosis will develop inflammation (irritation and swelling) in response to the initial infection. This can affect the skin, bones or joints, or the lining of the heart (pericardium). These symptoms are not due to fungal infection of those body parts, but to the inflammation.

In a small number of patients, histoplasmosis may become widespread (disseminated), and involve the blood, meninges (outer covering of the brain), adrenal glands, and other organs. Very young or very old people, or those who have a weakened immune system (due to AIDS, cancer, or transplant, for example) are at higher risk for disseminated histoplasmosis.

Symptoms

Symptoms depend on the type of infection:

  • Acute asymptomatic pulmonary (lung) histoplasmosis -- no symptoms
  • Acute symptomatic pulmonary histoplasmosis:
  • Chronic pulmonary histoplasmosis:
  • Disseminated histoplasmosis:
    • Fevers
    • Headache
    • Neck stiffness
    • Mouth sores
    • Skin lesions
  • Other histoplasma symptoms:

Exams and Tests

How histoplasmosis is diagnosed depends on the body parts involved. Tests may look at the sputum, lung tissue, blood, cerebrospinal fluid (CSF), or bone marrow for signs of the fungus. An antigen test may be done on blood, urine, or CSF.

In addition, x-rays may show abnormalities in the lungs or lymph nodes of the chest. These are signs of histoplasmosis.

Treatment

The main treatment for histoplasmosis is antifungal drugs. In the case of pulmonary histoplasmosis, this may include oral (taken by mouth) medicines such as itraconazole or ketoconazole.

Sometimes, especially in immunosuppressed people, long-term treatment with anti-fungal drugs are used after treatment with amphotericin.

Outlook (Prognosis)

What happens depends on the extent of the infection and the overall health of the individual. The death rate is fairly high for people with untreated widespread (disseminated) histoplasmosis, but is reduced significantly with treatment.

Possible Complications

  • Fibrosing mediastinitis -- scarring in the chest that may entrap the following body parts:
    • Great vessels (the major blood vessels carrying blood to and from the heart)
    • Esophagus (food pipe)
    • Heart
    • Lymph nodes
  • Inflammatory syndromes involving:
  • Mediastinal granuloma -- enlarged chest-cavity lymph nodes, which may compress body parts such as the esophagus and blood vessels of the lungs
  • Medication side effects (for example, amphotericin can have severe side effects)

In addition, people who have a weakened immune system may develop disseminated disease, which can infect the meninges of the brain (causing meningitis).

When to Contact a Medical Professional

Notify 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 the possibility of histoplasmosis.

Prevention

Minimize exposure to dust in contaminated environments such as chicken coops and bat caves. Wear protective equipment such as masks if you work in these environments.

References

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

Review Date: 9/28/2008
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; 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.
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