Histoplasmosis is a respiratory infection caused by the Histoplasma capsulatum fungus. After assessing medical and travel history and symptoms, then performing a physical examination, a doctor can order laboratory tests to help confirm a diagnosis.

Histoplasmosis occurs when a person comes into contact with spores from the Histoplasma capsulatum(H. capsulatum) fungus. The fungal spores circulate the air when a person starts digging into the ground.

The fungus lives in certain moist soils and damp environments. It is prevalent in endemic regions of Africa, Asia, central and southern America, and the Ohio and Mississippi River valleys in the United States.

To get an accurate diagnosis of histoplasmosis, the doctor may order multiple tests, including a lung biopsy, chest X-ray, CT scan, blood test, and urine test.

This article explains the different tests medical professionals can use to diagnose a histoplasmosis infection.

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Signs of histoplasmosis are typically mild, which can make it difficult to diagnose. Because of this, a doctor may use different diagnostic methods to help them identify and confirm a diagnosis of histoplasmosis. These tests can include:

Physical examination

A doctor will carry out a physical examination to assess the chest for pain. Histoplasmosis may also present with the following:

Blood test

If a person has histoplasmosis, a histoplasma complement fixation test will typically detect the presence of H. capsulatum.

Urine test

Doctors typically recommend a urinary antigen test as an initial screening for histoplasmosis. According to a 2018 study, urinary antigen testing may have a higher sensitivity than blood tests.

Skin test

A healthcare professional will clean an area of a person’s skin, typically on the forearm. They will then inject an allergen below the skin’s surface and check the site for signs of a reaction.

Lung biopsy

A doctor will take a small tissue sample from the lung through a minimally invasive surgical procedure. An expert will then study the lung tissue for signs of histoplasmosis.

Chest X-ray

A chest X-ray may show that a person has an infection. However, histoplasmosis can look similar to many other lung conditions, such as pneumonia, lung cancer, or tuberculosis.

CT Scan

This imaging scan can provide precise details of the lungs to help a doctor’s diagnosis of histoplasmosis. A lung infection may appear as abnormal growth in the lungs.

A person may experience mild flu-like symptoms 3–17 days after exposure to H. capsulatum. Symptoms typically affect the lungs. They may include:

The Centers for Disease Control and Prevention (CDC) note that symptoms of histoplasmosis will likely resolve within a few weeks to a month. However, if the infection is severe, some people may experience long lasting symptoms.

In people with a weakened immune system, histoplasmosis can cause a lung infection that can spread to other parts of the body.

Histoplasmosis is caused by fungal spores, found most commonly in the following areas:

  • demolition areas
  • shrubs
  • caves
  • chicken coops
  • damp or moist soil environments

According to the CDC, certain factors, such as particular medical conditions, may increase a person’s risk of developing histoplasmosis. These may include people who:

There are two types of histoplasmosis. They are:

Acute histoplasmosis

Acute histoplasmosis is typically mild and rarely leads to any severe complications.

Many people living in environments where the fungus is most common will have experienced exposure to the fungus without knowing.

Chronic histoplasmosis

Chronic (long-term) histoplasmosis occurs less frequently than the acute form. In rare instances, the infection can spread throughout the body.

Without treatment, chronic histoplasmosis can become life threatening if it spreads to other parts of the body. People who are immunocompromised may be at greater risk of chronic histoplasmosis.

According to the American Lung Association, most cases of histoplasmosis go away on their own in a few weeks without treatment. However, chronic histoplasmosis may require antifungal medication, including:

  • ketoconazole
  • amphotericin B
  • itraconazole

Treatment will depend on the severity of the infection and the person’s immune status. The course of treatment typically ranges from 3 months to 1 year.

It may be difficult to avoid histoplasmosis if a person lives in an environment where the H. capsulatum fungus is common. However, if a person has a weak immune system, they should try to limit their exposure by avoiding activities that may expose them to the fungus.

Learn more about antifungal drugs.

Histoplasmosis is a fungal condition caused by the H. capsulatum fungus. A blood test, urine test, skin test, biopsy, and chest X-ray can help a doctor diagnose histoplasmosis.

Symptoms can include fever, chills, headache, dry cough, and chest discomfort. Histoplasmosis will typically resolve on its own. However, in more severe cases, a doctor may administer antifungal medications to ease symptoms.