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Histoplasmosis is an infectious disease caused by inhaling the microscopic spores of the fungus Histoplasma capsulatum. The disease exists in three forms. Acute or primary histoplasmosis causes flulike symptoms. Most people who are infected recover without medical intervention. Chronic histoplasmosis affects the lungs and can be fatal. Disseminated histoplasmosis affects many organ systems in the body and is often fatal, especially to people with acquired immunodeficiency syndrome (AIDS).


Histoplasmosis is an airborne infection. The spores that cause this disease are found in soil that has been contaminated with bird or bat droppings. In the United States, the disease is most common in eastern and midwestern states and is widespread in the upper Mississippi, Ohio, Missouri, and St. Lawrence river valleys. Sometimes histoplasmosis is called Ohio Valley disease, Central Mississippi River Valley disease, Appalachian Mountain disease, Darling's disease, or Histoplasma capsulatum infection.
Anyone can get histoplasmosis, but people who come in contact with bird and bat excrement are more likely to be infected. This includes farmers, gardeners, bridge inspectors and painters, roofers, chimney cleaners, demolition and construction workers, people installing or servicing heating and air conditioning units, people restoring old or abandoned buildings, and people who explore caves.
The very young and the elderly, especially if they have a pre-existing lung disease or are heavy smokers, are more likely to develop symptoms that are more severe. People who have a weakened immune system, either from diseases such as AIDS or leukemia, or as the result of medications they take (corticosteroids, chemotherapy drugs), are more likely to develop chronic or disseminated histoplasmosis.

Causes and symptoms

When the spores of H. capsulatum are inhaled, they lodge in the lungs where they divide and cause lesions. This is known as acute or primary histoplasmosis. It is not contagious.
Many otherwise healthy people show no symptoms of infection at all. When symptoms do occur, they appear 3-17 days after exposure (average time is 10 days). The symptoms are usually mild and resemble those of a cold or flu; fever, dry cough, enlarged lymph glands, tiredness, and a general feeling of ill health. A small number of people develop bronchopneumonia. About 95% of people who are infected either experience no symptoms or have symptoms that clear up spontaneously. These people then have partial immunity to re-infection.
In some people, the spores that cause the disease continue to live in the lungs. In about 5% of people who are infected, usually those with chronic lung disease, diabetes mellitis, or weakened immune systems, the disease progresses to chronic histoplasmosis. This can take months or years. Symptoms of chronic histoplasmosis resemble those of tuberculosis. Cavities form in the lung tissue, parts of the lung may collapse, and the lungs fill with fluid. Chronic histoplasmosis is a serious disease that can result in death.
The rarest form of histoplasmosis is disseminated histoplasmosis. Disseminated histoplasmosis is seen almost exclusively in patients with AIDS or other immune defects. In disseminated histoplasmosis the infection may move to the spleen, liver, bone marrow, or adrenal glands. Symptoms include a worsening of those found in chronic histoplasmosis, as well as weight loss, diarrhea, the development of open sores in the mouth and nose, and enlargement of the spleen, liver, and adrenal gland.


A simple skin test similar to that given for tuberculosis will tell if a person has previously been infected by the fungus H. capsulatum. Chest x rays often show lung damage caused by the fungus, but do not lead to a definitive diagnosis because the damage caused by other diseases has a similar appearance on the x ray. Diagnosis of chronic or disseminated histoplasmosis can be made by culturing a sample of sputum or other body fluids in the laboratory to isolate the fungus. The urine, blood serum, washings from the lungs, or cerebrospinal fluid can all be tested for the presence of an antigen produced in response to the infection. Most cases of primary histoplasmosis go undiagnosed.


Acute primary histoplasmosis generally requires no treatment other than rest. Non-prescription drugs such as acetaminophen (Tylenol) may be used to treat pain and relieve fever. Avoiding smoke and using a cool air humidifier may ease chest pain.
Patients with an intact immune system who develop chronic histoplasmosis are treated with the drug ketoconazole (Nizoral) or amphotericin B (Fungizone). Patients with suppressed immune systems are treated with amphotericin B, which is given intravenously. Because of its potentially toxic side effects, hospitalization is often required. The patient may also receive other drugs to minimize the side effects of the amphotericin B.
Patients with AIDS must continue to take the drug itraconazole (Sporonox) orally for the rest of their lives in order to prevent a relapse. If the patient can not tolerate itraconazole, the drug fluconazole (Diflucan) can be substituted.

Alternative treatment

In non-immunocompromised patients, alternative therapies can be very successful. Alternative treatment for fungal infections focuses on creating an environment where the fungus cannot survive. This is accomplished by maintaining good health and eating a diet low in dairy products, sugars, including honey and fruit juice, and foods like beer that contain yeast. This is complemented by a diet high in raw food. Supplements of antioxidant vitamins C, E, and A, along with B complex, may also be added to the diet. Lactobacillus acidophilus and Bifidobacteria will replenish the good bacteria in the intestines. Antifungal herbs, like garlic, can be consumed in relatively large does and for an extended period of time in order to be most effective.


Most people recover from primary histoplasmosis in a few weeks without medical intervention. Patients with chronic histoplasmosis who are treated with antifungal drugs generally recover rapidly if they do not have an underlying serious disease. When left untreated, or if serious disease is present, histoplasmosis can be fatal.
AIDS patients with disseminated histoplasmosis vary in their response to amphotericin B, depending on their general health and how well they tolerate the side effects of the drug. Treatment often suppresses the infection temporarily, but patients with AIDS are always in danger of a relapse and must continue to take medication for the rest of their lives to keep the infection at bay. New combinations of therapies and new drugs are constantly being evaluated, making hard statistics on prognosis difficult to come by. AIDS patients have problems with multiple opportunistic infections, making it difficult to isolate death rates due to any one particular fungal infection.


Since the spores of H. capsulatum are so widespread, it is almost impossible to prevent exposure in endemic areas. Dust suppression measures when working with contaminated soil may help limit exposure. Individuals who are at risk of developing the more severe forms of the disease should avoid situations where they will be exposed to bat and bird droppings.

Key terms

Acidophilus — The bacteria Lactobacillus acidophilus, usually found in yogurt.
Adrenal gland — A pair of organs located above the kidneys. The outer tissue of the gland produces the hormones epinephrine (adrenaline) and norepinephrine, while the inner tissue produces several steroid hormones.
Antigen — A foreign protein to which the body reacts by making antibodies.
Bifidobacteria — A group of bacteria normally present in the intestine. Commercial supplements are available.
Corticosteroids — A group of hormones produced naturally by the adrenal gland or manufactured synthetically. They are often used to treat inflammation. Examples include cortisone and prednisone.



American Lung Association. 1740 Broadway, New York, NY 10019. (800) 586-4872. http://www.lungusa.org.
Histoplasmosis: Protecting Workers at Risk. Centers for Disease Control and Prevention. http://www.cdc.gov/niosh/97146eng.html.
National Center for Infectious Diseases. Atlanta, Georgia. (404) 639-3158. 〈http://www.cdc.gov/ncidod/ncid/ncid.htm〉.
National Institute for Occupational Safety and Health. Cincinnati, Ohio. (800) 356-4674.


Histoplasmosis: Protecting Workers at Risk. Centers for Disease Control and Prevention. http://www.cdc.gov/niosh/97146eng.html.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


a systemic fungal disease caused by inhalation of dust contaminated by Histoplasma capsulatum; it is not transmitted from one person to another. It is particularly common in rural areas of the midwestern United States, but is worldwide in distribution, including in urban areas. The infection begins in the lungs and may spread to other organs; it is usually asymptomatic but may cause acute pneumonia, disseminated reticuloendothelial hyperplasia with hepatosplenomegaly and anemia, or an influenzalike illness with joint effusion and erythema nodosum. Reactivated infection involves the lungs, meninges, heart, peritoneum, and adrenals in that order of frequency. On x-ray the lungs may resemble tuberculous lungs. The preferred drug for treatment of histoplasmosis is amphotericin b. In the USPHS/IDSA Guidelines for the Prevention of Opportunistic Infections in Persons with Human Immunodeficiency Virus, persons with HIV infection are cautioned to avoid activities associated with increased risk of exposure to Histoplasma capsulatum, such as cleaning chicken coops, disturbing soil underneath bird roosting sites, or exploring caves.
ocular histoplasmosis disseminated choroiditis resulting in scars in the periphery of the fundus near the optic nerve, and characteristic disciform macular lesions; Histoplasma capsulatum is implicated strongly as the causative agent.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


A widely distributed infectious disease caused by Histoplasma capsulatum; occurs occasionally in outbreaks; usually acquired by inhalation of spores of the fungus in soil dust and manifested by a self-limited pneumonia. In patients with emphysema, infection may be chronic and cause pulmonary fibrocavitary disease resembling tuberculosis; in immunosuppressed patients, and rarely, in otherwise healthy persons, histoplasmosis may cause disseminated disease of the reticuloendothelial system, which is manifested by fever, emaciation, splenomegaly, and leukopenia.
Synonym(s): Darling disease
Farlex Partner Medical Dictionary © Farlex 2012


n. pl. histoplasmo·ses (-sēz)
A disease caused by the inhalation of spores of the fungus Histoplasma capsulatum, most often asymptomatic but occasionally producing acute pneumonia or an influenzalike illness and spreading to other organs and systems in the body.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Infection by Histoplasma capsulatum, which is linked to inhalation of spore-laden dusts.

Clinical findings
Asymptomatic to an acute respiratory illness that evolves to chronic cavitary lung infection, the lesions of which may undergo calcification, to disseminated disease with low-grade fever, hepatosplenomegaly, lymphadenopathy and multiorgan involvement.
Elderly with COPD, immunocompromised hosts.
Patient travel history, serology (CF, immunodiffusion, latex agglutination to identify antibodies).

Amphotericin B.
Poor, despite therapy.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


Mycology Infection with Histoplasma capsulatum, 2º to inhalation of spore-laden dusts Clinical Asymptomatic to an acute respiratory illness that evolves to chronic cavitary lung infection–lesions may undergo calcification, to disseminated disease with low-grade fever, hepatosplenomegaly, lymphadenopathy and multiorgan involvement At-risk Elderly with COPD, immunocompromised hosts  Diagnosis Pt travel Hx, serology–CF, immunodiffusion, latex agglutination to identify antibodies Management Amphotericin B Prognosis Poor despite therapy.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


A widely distributed infectious disease caused by Histoplasma capsulatum and occurring frequently in epidemics; usually acquired by inhalation of spores of the fungus in soil dust and manifested by a primary benign pneumonitis; occasionally, the primary disease progresses to produce localized lesions in the lung, such as pulmonary cavitation, or the typical disseminated disease of the reticuloendothelial system that is manifested by fever, emaciation, splenomegaly, and leukopenia. Often spreads to the eye where it causes retinal lesions.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


A lung infection caused by the fungus Histoplasma capsulatum . The condition is usually mild and self-limiting, except in immunodeficient people who may develop a severe and sometimes fatal tuberculosis-like disease. Histoplasmosis is largely confined to limited areas of the United States of America, such as the Ohio basin.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005


Samuel Taylor, U.S. physician in Panama, 1872-1925.
Darling disease - a widely distributed infectious disease caused by Histoplasma capsulatum and manifested by a primary benign pneumonitis. Synonym(s): histoplasmosis
Medical Eponyms © Farlex 2012


An infection caused by inhalation of the fungus Histoplasma capsulatum found in soil dust. It manifests by a self-limited pneumonitis, which occasionally progresses and may affect the eye. It is then characterized by a disseminated choroiditis with small, yellowish scattered lesions called 'histo spots' which represent atrophic choroidal scars appearing as 'punched-out' spots. At a later stage the patient may present subretinal neovascularization with blurred vision. Many cases have been reported in parts of the world where the fungus is nonexistent. Thus the condition has been termed 'presumed ocular histoplasmosis syndrome (POHS)'. The main treatment for neovascularization consists of laser photocoagulation and steroids for the maculopathy.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann


Widely distributed infectious disease caused by Histoplasma capsulatum; occasional outbreaks; usually acquired by inhalation of fungal spores in soil dust.
Medical Dictionary for the Dental Professions © Farlex 2012
References in periodicals archive ?
Barnes, "Intravitreal anti-vascular endothelial growth factor therapy for choroidal neovascularization secondary to ocular histoplasmosis syndrome," Retina, vol.
Blinder, "Treatment of CNV secondary to presumed ocular histoplasmosis with intravitreal aflibercept 2.0 mg injection," Canadian Journal of Ophthalmology, vol.
(13) stated that anti-VEGF agents were beneficial in the treatment of CNV related to ocular histoplasmosis syndrome and found that these patients required an average of 4.5 intravitreal injections per year.
Intravitreal bevacizumab as initial treatment for choroidal neovascularization associated with presumed ocular histoplasmosis syndrome.
Ocular Histoplasmosis. In: Albert DM, Miller JW, Azar DT, Blodi BA, eds.
Bevacizumab treatment for choroidal neovascularization in a patient with chorioretinopathy resembling presumed ocular histoplasmosis syndrome.
Importance of proper diagnosis for management: multifocal choroiditis mimicking ocular histoplasmosis syndrome.
Gass, "Multifocal choroiditis and panuveitis: a syndrome that mimics ocular histoplasmosis," Archives of Ophthalmology, vol.
Claussen, "The long-term course of multifocal choroiditis (presumed ocular histoplasmosis)," American Journal of Ophthalmology, vol.