Histoplasmosis

Histoplasmosis is infection caused by the fungus Histoplasma capsulatum. It occurs mainly in the lungs but can sometimes spread throughout the body. 

• The infection is caused by inhaling spores of the fungus. 
• Most people do not have symptoms, but some feel sick and have a fever and cough, sometimes with difficulty breathing. 
• Sometimes the infection spreads, causing the liver, spleen and lymph nodes to enlarge and damaging other organs. 
• The diagnosis is based on culture and examination of tissue and fluid samples. 
• Whether treatment with antifungal drugs  is needed depends on  the severity of the infection. 

The spores of  Histoplasma are present in the soil and are particularly common in the eastern and midwestern United States, along the Ohio and Mississippi river valleys. Farmers and others who work with soil  are most likely to inhale the spores. Severe infection can result when large numbers of spores are inhaled. People with human immunodeficiency virus (HIV) infection are more likely to develop histoplasmosis, especially the  form that spreads through the bloodstream to other parts  of the body, such as the liver, spleen, lymph nodes, adrenal glands, digestive system,  and bone marrow. 

Symptoms

Most people with histoplasmosis do not develop any symptoms. However, the following three forms cause symptoms, as do some rare forms. 

Acute Pulmonary Histoplasmosis: Symptoms usually appear 3 to 21 days after people inhale the spores. People may feel sick, have a fever and a cough, and feel  as though they have  the flu. Symptoms usually disappear without treatment  in 2 weeks and rarely last longer than 6 weeks. 

This form  is very rarely fatal but can become serious in people with a weakened immune system (such  as those with AIDS). 

Progressive Disseminated Histoplasmosis: This form does not normally affect healthy adults. It usually occurs in infants or very  young children and in people  with a weakened immune system. Symptoms  are vague at first. People may experience fatigue, weakness, and a general feeling of illness (malaise). Symptoms may worsen very slowly or extremely rapidly. The liver, spleen, and lymph nodes may enlarge. Less commonly, the infection causes ulcers to form in the mouth and intestines. Rarely, the adrenal glands are damaged, causing Addison's disease.

Without treatment, this form is fatal in 90% of people. Even with treatment, death may occur rapidly in  people with AIDS.

Chronic Cavitary Histoplasmosis: This lung infection develops gradually over several weeks, causing a cough and increased difficulty breathing. Symptoms include weight loss, a mild fever, and a general feeling of illness (malaise). 

Most people recover without treatment within 2 to 6 months. However, breathing difficulties may gradually worsen, and some people cough up blood, sometimes  in large amounts. Lung tissue is destroyed,  and scar tissue forms. Lung damage  or bacterial invasion of  the lungs may eventually cause death. 

Diagnosis

To make  the diagnosis, a doctor obtains samples of  the sputum, bone marrow, urine,  or blood. Samples may also be taken  from the liver, lymph nodes, or any mouth ulcers that are present. These samples are sent to a laboratory  for culture and examination. Urine and blood may be tested for proteins (antigens) released by  the fungus. 

For some rare forms  of the infection,  the help of infectious disease specialists is required for diagnosis (and treatment). 

Treatment

People with acute pulmonary histoplasmosis rarely require drug treatment. However, fluconazole or itraconazole are often prescribed  to shorten  the duration  of the illness. 

People with progressive disseminated histoplasmosis need treatment  and often respond well to amphotericin B given intravenously or to itraconazole (or other related drugs) given by mouth. If people with AIDS develop histoplasmosis, they may need to take an antifungal drug, usually itraconazole, for  the rest of their life. However, they may be able  to stop the antifungal drug treatment if their CD4 count (a type of white blood cell) increases  and stays high enough for  at least 6 months. 

In chronic cavitary histoplasmosis, itraconazole or, for more serious infections, amphotericin B  may eliminate the fungus. However, treatment cannot reverse the destruction caused by the infection. Thus, most people continue to  have breathing problems, similar to those caused by chronic obstructive pulmonary disease. Therefore,  treatment should begin as soon as possible to limit  lung damage.