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Histoplasmosis |
| Definition: |
| Histoplasmosis is a fungal infection caused by Histoplasma capsulatum, which primarily affects the lungs but may spread to other organs.
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| Alternative Names: |
| Ohio River Valley fever
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| Causes, incidence, and risk factors: |
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Histoplasmosis is a fungal infection that can occur almost anywhere in the world. In the United States, it is most common in the southeastern, mid-Atlantic, and central states. The lungs are the portal of entry for this infection. Histoplasma grows as a mold in soil and infection results from inhalation of airborne fungal particles. Soil contaminated with bird or bat droppings may have a higher concentration of mold. Histoplasmosis may have no symptoms, there may be a short period of active infection or it can become chronic and spread throughout the body. Most patients with symptomatic histoplasmosis will have a flu-like syndrome and pulmonary (lung) complaints related to underlying pneumonia or other lung involvement. Individuals with chronic lung disease (e.g., emphysema, bronchiectasis) may be at higher risk of a more severe infection. If the body responds to infection with extreme inflammation (irritation and swelling with presence of extra immune cells in affected area), up to 10% of patients may have complications involving the skin, bone/joints, or the lining of the heart (pericardium). In a small proportion of patients, histoplasmosis may be widespread (disseminated histoplasmosis) and involve the blood, meninges (linings of the brain), adrenal glands, and other organs. Very young or very old people or those who have underlying immune disorders such as AIDS are at higher risk for disseminated histoplasmosis. |
| Symptoms: |
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Symptoms depend on the underlying clinical syndrome:
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| Signs and tests: |
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The diagnosis of histoplasmosis depends on the underlying condition. Tests may include analysis of the organism in sputum, lung tissue, blood, cerebrospinal fluid (CSF), or bone marrow tissue, as well as antigen tests performed on blood, urine, or CSF. In addition, certain pathologic findings may be seen in tissue which may support the diagnosis of histoplasmosis. |
| Treatment: |
| The mainstay of therapy for histoplasmosis is antifungal therapy. In the case of pulmonary histoplasmosis, this may include oral agents such as itraconazole or ketoconazole. In disseminated disease -- particularly meningitis -- therapy with intravenous amphotericin is used followed by long-term suppression with an oral agent such as itraconazole. |
| Expectations (prognosis): |
| Prognosis depends on the clinical syndrome -- mortality is highest in disseminated histoplasmosis (up to 80% without treatment -- decreased to 25% with treatment). |
| Complications: |
In individuals with weakened immune systems disseminated disease may occur and involve the meninges (meningitis) Side effects of medications (can be severe with amphotericin) are complications of histoplasmosis. |
| Calling your health care provider: |
| Notify your medical provider if you live in an endemic area for histoplasmosis and you develop flu-like symptoms, chest pain, cough and shortness of breath. While there are many other illnesses that may have similar symptoms, you may need to be evaluated 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. |
Reviewed By: Camille Kotton, M.D., Infectious Diseases Division, Massachusetts General Hospital and Brigham and Women's Hospital, Boston, MA. Review provided by VeriMed Healthcare Network.
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