CNN

Several types of histoplasmosis exist, ranging from mild to life-threatening. The mildest form produces no signs or symptoms, but severe infections can cause serious problems throughout your body as well as in your lungs. When signs and symptoms do occur, they usually appear three to 17 days after exposure.

Asymptomatic primary histoplasmosis
This is the most common form of histoplasmosis and usually causes no signs or symptoms in otherwise healthy people who become infected. The only sign that you were ever infected may be small scars in the lungs.

Acute symptomatic pulmonary histoplasmosis
This form of histoplasmosis tends to occur in otherwise healthy people who've had intense exposure to H. capsulatum. Because the severity of the disease depends on the number of fungus spores inhaled, reactions may range from a brief period of not feeling well to serious illness. Typical signs and symptoms include:

• Fever
• Muscle aches
• Headache
• Dry cough
• Chills
• Chest pain
• Loss of appetite
• Sweats

In some cases, the following may also accompany acute symptomatic pulmonary histoplasmosis:

• Arthritis.
• Inflammation of the sac that surrounds the heart (pericarditis).
• Severe acute pulmonary syndrome, a potentially life-threatening condition in which breathing becomes difficult. Also called spelunker's lung, this often occurs after prolonged exposure to bat excrement stirred up by explorers in caves.

Arthritis and pericarditis don't mean that the infection has spread outside your lungs. Instead, they develop because your immune system responds to the fungus with an unusual amount of inflammation.

Chronic pulmonary histoplasmosis
This type of histoplasmosis usually affects people with an underlying lung disease, such as emphysema. The disease is chronic and if left untreated may progress to disabling lung problems. Signs and symptoms include:

• Fever
• Night sweats
• A cough that may bring up blood
• Shortness of breath
• Weight loss

Disseminated histoplasmosis
Occurring primarily in infants and people with compromised immune systems, disseminated histoplasmosis can affect nearly any part of your body, including your eyes, liver, bone marrow, central nervous system, skin, adrenal glands and intestinal tract. Untreated disseminated histoplasmosis is usually fatal. Depending on which organs are affected, people with this form of the disease may develop:

• Fever
• Weight loss
• Enlarged spleen
• Enlarged liver
• Pneumonia
• Inflammation of the sac surrounding the heart (pericarditis)
• Inflammation of the thin membrane that covers the brain and spinal cord (meningitis)
• Poorly functioning adrenal glands (adrenal insufficiency)
• Ulcers of the mouth, tongue or intestinal tract

When to see a doctor
Contact your doctor if you live in an area where histoplasmosis is common — such as the Ohio and Mississippi river valleys of North America — and you develop chest pain, cough and a fever. Although many illnesses cause similar signs and symptoms, your doctor may want to test you for the presence of H. capsulatum. If your immune system has been weakened by illness or medications, and you develop any symptoms of histoplasmosis, seek medical care immediately.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Histoplasmosis is caused by the reproductive cells (spores) of the fungus Histoplasma capsulatum. The spores are extremely light and float into the air when dirt or other contaminated material is disturbed.

Histoplasmosis and your lungs
Because the spores of H. capsulatum are microscopic in size, they can easily enter your lungs and settle in the small air sacs. There, the spores are trapped by macrophages — immune system cells that attack foreign organisms. The macrophages carry the spores to lymph nodes in your chest, where they continue to multiply. This may lead to inflammation, scarring and calcium deposits. In cases of heavy infection, the lymph nodes may become so enlarged that they obstruct your esophagus or your lungs' airways.

Most often, however, you're not likely to have noticeable signs and symptoms, and the infection clears on its own without treatment. But if your immune system isn't able to eliminate the spores, they can enter your bloodstream and travel to other parts of your body. In that case, you may develop a variety of severe problems that can be fatal if not diagnosed and treated quickly.

Even if you've had histoplasmosis in the past, you can still get the infection again. However, if you contract histoplasmosis again, the illness will likely be milder than the initial infection.

Where the fungus lives
Histoplasma capsulatum is primarily found in the temperate regions of the world. It's very common in the Ohio and Mississippi river valleys of North America, where many people have already been exposed to the fungus.

It thrives in damp soil that's rich in organic material, especially the droppings from birds and bats. For that reason, it's particularly common in chicken and pigeon coops, old barns, caves and parks.

Birds themselves aren't infected with histoplasmosis — their body temperature is too high — but they can carry H. capsulatum on their feathers, and their droppings support the growth of the fungus. Birds commonly kept as pets, such as canaries and parakeets, aren't affected. And although bats, which have a lower body temperature, can be infected, you can't get histoplasmosis directly from a bat or from another person.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Anyone exposed to H. capsulatum is likely to become infected. People who inhale a huge number of spores — those who work with heavily infected soil or have close contact with bat droppings, for example — are more likely to develop signs and symptoms.

Most at risk of infection

• Farmers
• Pest control workers
• Poultry keepers, especially when cleaning chicken coops, pigeon roosts, and bat-infested barns or lofts
• Construction workers, especially those who work around old buildings with roosting birds
• Roofers
• Landscapers and gardeners
• People involved in building roads and maintaining bridges
• People who monitor bird populations or who have contact with bats or bat caves
• Archeologists
• Geologists

Most at risk of severe infection
Because their immune systems are weakened, the following people are most likely to develop disseminated histoplasmosis, the more serious form of the disease:

• Infants and very young children
• Older adults
• People with HIV or AIDS
• People receiving chemotherapy or long-term treatment with corticosteroid drugs such as prednisone
• People who have had organ transplants and are taking anti-rejection medications

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Histoplasmosis can cause a number of serious complications, even in otherwise healthy people. For infants, older adults and people with compromised immune systems, the potential problems are often life-threatening.

• Enlarged lymph nodes. Most people with histoplasmosis have some involvement with the lymph nodes in the central part of the chest. This region lies between your lungs and contains the trachea, esophagus, heart and many small lymph nodes. In a small percentage of people with acute pulmonary histoplasmosis, the lymph nodes may enlarge enough to obstruct the airways or esophagus, making it difficult to breathe or swallow. Sometimes the pulmonary arteries and veins — the large blood vessels in the lungs — also may be blocked.
• Severe scarring. A rare, severe late complication of histoplasmosis called fibrosing mediastinitis occurs when scar tissue from lymph nodes in the chest invades and blocks adjoining structures, especially the esophagus and large blood vessels. Signs and symptoms, such as a cough that brings up blood, chest pain and breathlessness, usually don't appear until the disease is quite advanced. When structures in both lungs are affected, fibrosing mediastinitis can be life-threatening.
• Heart problems. Inflammation of the pericardium, the sac that surrounds your heart, is called pericarditis. Normally, this sac contains a small amount of fluid. But when the pericardium becomes inflamed, the amount of fluid in the sac may increase, which can interfere with the heart's ability to pump blood efficiently. Pericarditis that occurs as a complication of histoplasmosis usually results from inflammation in nearby lymph nodes, rather than from actual infection of the pericardium itself.
• Arthritis. Joint inflammation, sometimes in conjunction with a skin rash (erythema nodosum), is a common complication of acute pulmonary histoplasmosis. Women are far more likely to be affected than are men.
• Adrenal insufficiency. Your adrenal glands, which are located just above your kidneys, produce hormones that give instructions to virtually every organ and tissue in your body. A histoplasmosis infection can cause destruction of the adrenal glands. When the glands don't provide enough of these hormones, serious, and potentially life-threatening, problems can occur. Untreated adrenal insufficiency (Addison's disease) is fatal.
• Meningitis. An infection and inflammation of the membranes (meninges) and fluid (cerebrospinal fluid) surrounding your brain and spinal cord, meningitis can be life-threatening. As a complication of histoplasmosis, meningitis occurs primarily in people with compromised immune systems, although it occasionally develops in otherwise healthy people.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

You're likely to start by first seeing your family doctor or a general practitioner. However, you may then be referred to a doctor who specializes in infectious diseases. Depending on your symptoms and the severity of your infection, you may also see other doctors, such as a lung specialist (pulmonologist) or a heart specialist (cardiologist).

Here's some information to help you get ready for your appointment, and what to expect from your doctor.

What you can do

• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including any possible exposure to areas with numerous birds or bats.
• Make a list of all medications, vitamins and supplements that you're taking.
• Write down questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions can help you make the most of your time together. List your questions from most important to least important in case time runs out. For histoplasmosis, some basic questions to ask your doctor include:

• What's the most likely cause of my symptoms?
• How could I have gotten this infection?
• What kinds of tests do I need? Do these tests require any special preparation?
• Will this infection get better on its own or do I need treatment?
• What treatments are available, and which do you recommend?
• What types of side effects can I expect from treatment?
• Are there any alternatives to the primary approach that you're suggesting?
• I have other health conditions. How can I best manage them together?
• Is there a generic alternative to the medicine you're prescribing me?
• Can I get infected again?
• Are there any brochures or other printed material that I can take home with me? What Web sites do you recommend visiting?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

• When did you first begin experiencing symptoms?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• Do you work outdoors?
• Have you spent an extended time in areas with large populations of birds?
• Have you spent any time in caves? Or other areas where bats might congregate?

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Histoplasmosis can cause a variety of signs and symptoms, many of which resemble those of other illnesses. For that reason, it can be particularly challenging to diagnose. Complicating the matter further is the large number of tests available for detecting the presence of the fungus — each of which has some limitations. These tests include:

• Fungal culture. This is considered the gold standard for confirming a diagnosis of histoplasmosis. During the test, a small amount of blood, mucus or tissue from your lymph nodes, lungs or bone marrow is placed on a medium that enhances the growth of fungus and is then checked for the presence of H. capsulatum. The drawback is the time it takes for the fungus to grow — up to four weeks. For that reason, it's not a good choice in cases of disseminated disease where delayed treatment may prove fatal.
• Fungal stain. In this test, a tissue sample, which may be taken from mucus, bone marrow, your lungs or a skin sore, is stained with dye and examined under a microscope. The accuracy of the test depends on the type of sample obtained and the skill and experience of the examiner. Other organisms can resemble H. capsulatum under the microscope, so confirmation with another test is desirable if an organism resembling H. capsulatum is identified.
• Urine and blood tests. Antigens and antibodies can be found in your urine and blood. It's a quick and fairly accurate way of detecting disseminated histoplasmosis as well as chronic or mild cases of the disease. But false-negative results are a problem, especially in people who have compromised immune systems or are infected with other types of fungi. The test can also be positive in people who live in areas where histoplasmosis is common and have had past exposure to H. capsulatum, even though their current symptoms may be due to something else.

Depending on your signs and symptoms and the severity of your illness, your doctor may recommend other tests, such as:

• Chest X-ray. Although not normally used to definitively diagnose histoplasmosis, an ordinary chest X-ray can show inflammation and damage in your lungs.
• Computerized tomography (CT). This X-ray technique produces more-detailed images than do standard X-rays. CT can be especially helpful for detecting complications from histoplasmosis.
• Bronchoscopy. Your doctor may use this test to help establish a diagnosis of histoplasmosis if the disease hasn't already been confirmed by a fungal culture, stain or blood test. During the procedure, your doctor examines your windpipe (trachea) and the air passages leading to your lungs using a thin, lighted tube (endoscope). A small sample of tissue (biopsy) can be taken through the endoscope.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Treatment usually isn't necessary if you have a mild case of acute histoplasmosis. But if your symptoms are severe or you have the chronic or disseminated forms of the disease, you'll likely need treatment with one or more antifungal medications — most often amphotericin B (Fungizone IV) and itraconazole (Sporanox). The specific drug and the length of treatment depend on the type and severity of your illness as well as on your overall health.

In general, one of several formulations of amphotericin B is the initial treatment of choice for people with disseminated histoplasmosis or severe disease. But because these drugs can be toxic to the kidneys and must be administered intravenously, doctors usually switch to itraconazole within a few days to a few weeks, depending on how your condition improves. Corticosteroids are also sometimes given initially if you have severe respiratory disease and difficulty maintaining oxygen levels in your bloodstream.

Itraconazole alone may be effective in mild cases of disseminated histoplasmosis as well as in chronic pulmonary disease. Although itraconazole doesn't work as quickly as amphotericin B, it has fewer side effects and can be taken in pill form. While using this medication, you may experience headache, dizziness, nausea, vomiting or diarrhea, but these symptoms often go away over time. If you have a history of liver or kidney problems, or another lung disease, you'll need to be monitored closely during treatment.

If you're not a candidate for itraconazole or can't tolerate the medication, your doctor may prescribe fluconazole (Diflucan), another antifungal drug. Fluconazole isn't as effective as itraconazole, however, and you're more likely to experience a relapse with this medication.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

It's difficult to prevent exposure to the fungus that causes histoplasmosis, especially in areas where the disease is widespread. Even so, these steps can help reduce the risk of infection:

• Spray contaminated soil. Before you work in or dig soil that's likely to harbor H. capsulatum, spray it thoroughly with water. This can help prevent spores from being released into the air. Spraying chicken coops and barns before cleaning them also can reduce your risk.
• Use an effective face mask. One of the best ways to protect yourself from soil-borne organisms if you must work in contaminated areas or in caves known to harbor bats is to wear personal protective equipment. The National Institute for Occupational Safety and Health (NIOSH) recommends wearing a well-fitting part 84 particulate respirator certified by NIOSH.

If your immune system is compromised, avoid renovation projects that might expose you to contaminated soil. Likewise, cave exploring and raising birds, such as pigeons or chickens, aren't advised.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.