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Histoplasmosis

Definition

Histoplasmosis is an infection due to the Histoplasma capsulatum fungus.

Alternative Names

Ohio River Valley fever

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.

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:
    • Chest pain
    • Cough, possibly coughing up blood
    • Fever
    • Shortness of breath
    • Sweating
  • Disseminated histoplasmosis:
    • Fevers
    • Headache
    • Neck stiffness
    • Mouth sores
    • Skin lesions
  • Other histoplasma symptoms:
    • Joint pain
    • Rashes
    • Skin nodules (red lumps called erythema nodosum), most often on the lower legs

Signs and tests

How histoplasmosis is diagnosed depends on the body parts involved. Tests that may be done include:

  • Skin biopsy
  • Blood, urine, or sputum tests to look for signs of histoplasmosis infection
  • Chest CT scan
  • Chest x-ray
  • Spinal tap to look for signs of infection in cerbrospinal fluid (CSF)

Treatment

The main treatment for histoplasmosis is antifungal drugs. Amphotericin B, itraconazole, and ketoconazole are the usual treatments.

Antifungals may be given through a vein, depending on the form or stage of disease.

In some cases, long-term treatment with antifungal drugs may be needed.

Expectations (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.

Complications

  • Fibrosing mediastinitis -- scarring in the chest that may entrap the following body parts:
    • 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).

Calling your health care provider

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

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.

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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