Encyclopedia - Histoplasmosis

How is histoplasmosis spread?
How is histoplasmosis treated?

Histoplasmosis is an infectious disease of the lungs that can spread to other parts of the body. Caused by a fungus, it is not contagious from one person to another.

Because the disease and its organisms thrive in moderate temperatures and moist environments, this infection is most common in the Midwestern United States, particularly in areas where bird or bat droppings accumulate. Ninety percent of adults infected with histoplasmosis live in Arkansas, Kentucky, Missouri, Tennessee, Alabama, Iowa, Illinois, West Virginia, Oklahoma, Ohio, Nebraska, Louisiana, Kansas, Mississippi, Maryland, Texas, and Virginia.

For many individuals, histoplasmosis is no more threatening than the common cold. For others, however, histoplasmosis, even in its mildest form, can spread from the lungs to the eyes, causing Ocular Histoplasmosis Syndrome (OHS).

How is histoplasmosis spread?

When the soil is plowed or disturbed, the microscopic spores of the fungus are released into the air. When the fungus reaches the eye, it finds its "home" in the layer of blood vessels that provide blood and nutrients to the eye and causes abnormal blood vessels to develop under the retina. As these new vessels develop, they form lesions that can turn into scar tissue. This scar tissue replaces healthy tissue in the macula -- the part of the eye responsible for clear, precise vision -- thus resulting in vision loss. Ocular Histoplasmosis Syndrome rarely causes complete blindness.

How is histoplasmosis treated?

Symptoms of histoplasmosis are usually so mild and it passes so fast that patients seldom recognize a serious problem. However, in the advanced stages of OHS, patients may report a blind spot or see wavy lines that really are straight. A comprehensive eye exam can reveal "histo spots," which are spots that remain at the infection site even after the infection has cleared.

A diagnosis is important because the infection can cause late recurring problems. Patients suspecting histoplasmosis exposure should see an eye care professional immediately.

The only treatment for OHS is laser surgery. A small, intense light beam targets the abnormal blood vessels and any scar tissue caused by the lesions. It's important to note, however, that OHS can be controlled with this surgery, but not cured.