Histoplasmosis (cont.)
Charles Patrick Davis, MD, PhD
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
Melissa Conrad Stöppler, MD
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
In this Article
- What is histoplasmosis?
- What causes histoplasmosis?
- What are the symptoms and signs of histoplasmosis?
- Are there different types of histoplasmosis?
- How is histoplasmosis transmitted?
- How is histoplasmosis diagnosed?
- How is histoplasmosis treated?
- What are the complications seen with histoplasmosis?
- How is histoplasmosis prevented?
- What is the prognosis (outlook) for people with histoplasmosis?
- Where is more information available on histoplasmosis?
- Histoplasmosis At A Glance
What causes histoplasmosis?
Histoplasmosis is caused by a dimorphic (two forms, mycelia and yeast) fungus named Histoplasma capsulatum. The genus name is misleading; the fungus has no capsule, but early investigators mistakenly thought it did. The mycelial phase consisting of mycelia fragments and spores can be inhaled and may reach the lung alveoli. Macrophages (human phagocytic cells of the immune system) surround and engulf (phagocytosis) H. capsulatum, which then changes inside the macrophages to the yeast form in about 15-18 hours. In most cases, the macrophage response kills the yeast. When macrophages fail to kill all the yeast, a variation of the disease develops because the yeast form multiplies and invades other cells. The larger the number of mycelia and spores the person is exposed to, the more likely the person will develop symptomatic disease.
What are the symptoms and signs of histoplasmosis?
About 90% of infections caused by H. capsulatum are asymptomatic (produce no symptoms). Occasionally, a few asymptomatic patients will show small scars in lung X-rays. Symptomatic people often develop fever, chills, dry cough, malaise, sweats, and abdominal pains about three to 14 days after exposure. If the disease progresses, symptoms such as weight loss, fatigue, dyspnea, chest pain, and reduced or loss of vision may occur. A sign of progression are patchy infiltrates seen on chest X-rays, usually in the lower lung fields. Other symptoms that can occur, especially in patients that are immunosuppressed, are mouth ulcers, fevers, headaches, confusion, seizures, encephalopathy, and infrequently, death.
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