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Acute Pulmonary Histoplasmosis

Last updated Nov. 15, 2019

Approved by: Maulik P. Purohit MD, MPH

Acute Pulmonary Histoplasmosis is an infectious disease that primarily affects the respiratory system (lung and airways).


What are the other Names for this Condition? (Also known as/Synonyms)

  • Acute Histoplasmosis
  • Acute Infection by Histoplasma Capsulatum 

What is Acute Pulmonary Histoplasmosis? (Definition/Background Information)

  • Acute Pulmonary Histoplasmosis is an infectious disease that primarily affects the respiratory system (lung and airways). It commonly occurs by inhaling the spores of a fungus called Histoplasma capsulatum
  • This fungus spreads through bird and bat droppings that fall on the soil. Eventually, the spores spread through the soil and enter into the human body through inhalation
  • Individuals with a weak immune system are more at risk of serious disease and usually require treatment by antifungal medications
  • The common signs and symptoms associated with Acute Pulmonary Histoplasmosis include fever, cough, breathing difficulties, muscle aches, skin rashes, and pain in the joints
  • The diagnosis of the condition is made by a combination of lab tests (such as detecting histoplasma antigen in urine) and imaging studies that include chest x-ray and CT scan of the chest
  • The majority of the individuals with a competent immune system do not need any treatment and the infection clears on its own. However, those with poor immune systems need to be watched closely for disseminated infection or severe forms of the infection, which can be fatal, if not treated properly
  • The prognosis of Acute Pulmonary Histoplasmosis is excellent with appropriate treatment in most cases 

Who gets Acute Pulmonary Histoplasmosis? (Age and Sex Distribution)

  • Acute Pulmonary Histoplasmosis can occur at any age, but very young children and older adults are more likely to be affected by this infection
  • There is no gender predilection and both males and females are at equal risk
  • All racial and ethnic groups can be affected
  • Histoplasmosis is a condition that is seen mainly within the central and eastern parts of United States, as well as in the eastern areas of Canada
  • Some areas of Mexico, Central American, South America, Africa, and Southeast Asia also have an increased incidence

What are the Risk Factors for Acute Pulmonary Histoplasmosis? (Predisposing Factors)

The following risk factors are associated with Acute Pulmonary Histoplasmosis:

  • Very young children and elderly adults with weaker immune system
  • Individuals with weak immune system, such as HIV patients and those on immunosuppressive drugs after organ transplantation
  • Acute Histoplasmosis is mainly seen in the central and eastern parts of United States as well as in the eastern areas of Canada. Those in the endemic regions have a high risk of infection
  • People living in areas near the Ohio River Valley
  • Exploring caves, especially bat caves in the endemic regions
  • Those with occupations, such as construction workers, farmers, roofers, and landscapers, working in the endemic region
  • Many studies have demonstrated that there is an increased chance of infection for people living in old, torn down buildings, in the endemic regions

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider. 

What are the Causes of Acute Pulmonary Histoplasmosis? (Etiology)

Acute Pulmonary Histoplasmosis is caused by the fungus Histoplasma capsulatum, in a majority of the cases.

  • There are other types of Histoplasma fungus that can cause infection in humans
  • This fungus is usually transmitted by bats or birds in the endemic regions
  • The infection is spread by bird and bat droppings, which is transmitted to humans through inhalation
  • The fungal spores enter the human body through inhalation and affects the respiratory system causing an infection

What are the Signs and Symptoms of Acute Pulmonary Histoplasmosis?

Histoplasmosis does not cause any significant signs and symptoms in most individuals with good and healthy immune systems. Even though mild flu-like symptoms may be present, most individuals may not even be aware of the fungal infection.

The signs and symptoms associated with Acute Pulmonary Histoplasmosis (in those having weak immunity) may include:

  • Chest tightness
  • Breathing difficulties
  • Productive cough
  • Fever
  • Muscle pain, generalized body aches
  • Skin rashes that usually occur on the lower legs; though, other parts of the body may be affected too
  • Pain in the joints

How is Acute Pulmonary Histoplasmosis Diagnosed?

The diagnosis of Acute Pulmonary Histoplasmosis may include:

  • Complete evaluation of medical history along with a thorough physical exam
  • Culture of body fluids, such as sputum, to identify the fungus
  • Detection of histoplasma antigen in urine
  • Blood test to measure antibodies in blood against the fungus
  • Imaging studies, such as chest x-rays and CT scan of the chest, are also helpful in diagnosing Acute Pulmonary Histoplasmosis
  • Bronchoscopy: It is a surgical procedure in which the airways and lungs are examined with the help of a scope and simultaneously tissue is also taken for biopsy (examination under microscope by the pathologist)

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis. 

What are the possible Complications of Acute Pulmonary Histoplasmosis?

The possible complications that are associated with Acute Pulmonary Histoplasmosis include:

  • Progression to chronic form of the infection called chronic pulmonary histoplasmosis
  • Spread of infection to other organs, especially in those with suppressed immune system, a condition known as disseminated histoplasmosis

How is Acute Pulmonary Histoplasmosis Treated?

For many individuals with competent immune system, no treatment is necessary for Acute Pulmonary Histoplasmosis, as they are able to clear the infection without any treatment. Antifungal medications to treat the infection may be required in the following scenarios:

  • Individuals with weak immune system
  • If the symptoms persist for more than 4 weeks
  • In case of breathing difficulties and the presence of significant signs and symptoms

How can Acute Pulmonary Histoplasmosis be Prevented?

Acute Pulmonary Histoplasmosis may be prevented using the following precautions:

  • In the endemic regions, the risk of the condition is high in individuals with suppressed/weak immune system. Hence, those with weak immune systems should:
    • Avoid exposure to soil in areas with high risk of fungal spores
    • Avoid exploring bat caves         
    • Get early symptoms of the disease appropriately treated
  • Individuals with weak immune system should get appropriate treatment as soon as possible, after a diagnosis of the condition is confirmed 

What is the Prognosis of Acute Pulmonary Histoplasmosis? (Outcomes/Resolutions)

  • The outcome of Acute Pulmonary Histoplasmosis is excellent in individuals with a strong and robust immune system. In such individuals, the infection causes flu-like symptoms that get better on its own without any treatment
  • Individuals with weak immune systems are more at risk for developing disseminated forms of the disease. Also, if the condition progresses to its chronic form, then it can become a life-threatening condition
  • The damage due to acute forms of histoplasmosis is usually reversible and such individuals are able to recover completely 

Additional and Relevant Useful Information for Acute Pulmonary Histoplasmosis:

The following DoveMed website link is a useful resource for additional information:

https://www.dovemed.com/diseases-conditions/infection-center/

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Sept. 24, 2015
Last updated: Nov. 15, 2019