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Definition: histoplasmosis from Merriam-Webster's Collegiate(R) Dictionary

(1907) : a respiratory disease with symptoms like those of influenza that is caused by a fungus (Histoplasma capsulatum) and is marked by benign involvement of lymph nodes of the trachea and bronchi or by severe progressive generalized involvement of the lymph nodes and tissues (as of the liver or spleen) rich in macrophages

Summary Article: Histoplasmosis: Cave Disease
from The 101 Most Unusual Diseases and Disorders
  • Located throughout the world and in the United states; common in Southeastern, mid-Atlantic, and Central states

  • Fungus found in soil and other areas associated with bat guano or bird droppings

  • Affects the lungs but may go into other organs

  • Often misdiagnosed

The bats had invaded the attic of the middle school. At night, one could see thousands of bats flying around the area of the building. During the day they went into the attic and settled above one particular room. This was the room where Janie taught math. The room had a terrible stench; brown droppings from the bats streaked one wall.

Students and teachers complained, but the comment they received was, “We can't get rid of the bats.” Finally, a school board member threatened to have the health department shut the school down unless something was done. The district found a way. In all, Janie had been complaining about the condition of the room for three years. Janie suffered with health problems and missed a lot of school. She had coughs and lung infections. Later, she developed kidney problems and cancer behind the sternum that could not be treated. When she died, she was tested for histoplasmosis. Tests were positive; she had the antibodies for histoplasmosis. No one had detected it, and the school district appeared not aware of the danger to the teacher and to students.

Although it is rare, it is often misdiagnosed, because people may not make the connection of being in a contaminated area or in a cave. Janie never told the doctors that she taught in the room with a bat problem. It only came out after her death.


Histoplasmosis is an infection caused by the fungus Histoplasma capsulatum. This organism grows as a mold in the soil or other areas, and like other molds it gives off spores. If people breathe these spores, they may get sick, usually from some type of lung infection. The area in the soil is associated with decaying bat guano or bird droppings. If these bat guano or bird droppings are in areas where new excavation is disturbing the mold, spores are released into the air. It is especially found in caves, in which cave explorers or spelunkers may disturb soil that has not been moved for years.

In 1903, efforts to build the Panama Canal were being thwarted by diseases such as yellow fever and malaria. That same year Samuel Taylor Darling (1872–1925) graduated from medical school and went to study tropical disease in the area. Walter Reed found that the mosquito carried the two main diseases, but another was causing havoc with the lungs and other body systems of the workers. In the 1930s, Darling autopsied workers who had died from the unusual lung disorder, and discovered a fungus was present in the lungs of the men. He concluded that the widespread lung and body infection was caused by spores of this fungus, which the men had breathed in.

The word “histoplasmosis” comes from the Greek terms: histo, meaning “tissue,” plasm, meaning “form” or “mold,” and osis, meaning “condition of.” Although referred to as histoplasmosis, it is also known as Darling's disease.

The mold grows in the soil or in litter near where birds or bats have been. The litter around bird roosts, chicken houses, caves, or an area harboring bats may harbor the mold. Molds reproduce by forming mycelia that have spores on the end. These spores break off and go into the air. If inhaled by a human, at 37°C, it morphs into a yeast and finds its way into the alveoli or air sacs of the lungs. In the lungs, it is attacked by macrophages, a type of antibody. Macrophages travel in the lymphatic system to other organs of the body. If the patient has a strong immune system, the invaders will be calcified, but if the person has some other type of condition that has compromised the immune system, it will spread to the other organs and infect them. However, the lungs can develop a chronic disease.


Some people may have no symptoms; others may have symptoms that resemble many other diseases: fever, chills, cough, chest pain that gets worse when breathing, joint pain, mouth sores, and red bumps on the skin. Symptoms can begin within three to 17 days after exposure, with an average of 12 to 14 days. The acute phase is like flu with respiratory infection, which goes away after several days.

For others, the infection may become chronic. The person has chest pain and shortness of breath, cough with spitting up blood, and fever and sweating. In addition, it may spread throughout the body and affect the lining around the heart or pericardium and present headache and neck stiffness form swelling in the meninges covering the brain and spinal cord.


The doctor may order a biopsy of the lung, skin, liver, or bone marrow, as well as blood and urine tests. A sputum test may provide the clearest results but can take over 6 weeks to be processed. Other tests may include X-ray of chest, chest CT (computed tomography) scan, bronchosopy, and a spinal tap to look for signs of infection.


If the person has a strong immune system, the condition may go away without any treatment. Antifungal medications such as amphotericin B followed by oral itraconazole or ketoconazole are usual treatments. However, these medications may cause side effects. In severe cases, treatment may last up to a year.

For Further Information
  • Daniel, Thomas M.; Gerald L. Baum. Drama and Discovery: The Story of Histoplasmosis. Praeger Santa Barbara CA, 2002.
  • Copyright © 2015 Evelyn B. Kelly

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