Alternative names
Ohio River Valley fever

Definition
Histoplasmosis is a fungal infection caused by Histoplasma capsulatum, which primarily affects the lungs but may spread to other organs.

Causes, incidence, and risk factors

Histoplasmosis is a fungal infection that can occur almost anywhere in the world. In the United States, it is most common in the southeastern, mid-Atlantic, and central states.

The lungs are the portal of entry for this infection. Histoplasma grows as a mold in soil and infection results from inhalation of airborne fungal particles. Soil contaminated with bird or bat droppings may have a higher concentration of mold.

Histoplasmosis may have no symptoms, there may be a short period of active infection or it can become chronic and spread throughout the body. Most patients with symptomatic histoplasmosis will have a flu-like syndrome and pulmonary (lung) complaints related to underlying pneumonia or other lung involvement. Individuals with chronic lung disease (e.g., emphysema, bronchiectasis) may be at higher risk of a more severe infection.

If the body responds to infection with extreme inflammation (irritation and swelling with presence of extra immune cells in affected area), up to 10% of patients may have complications involving the skin, bone/joints, or the lining of the heart (pericardium).

In a small proportion of patients, histoplasmosis may be widespread (disseminated histoplasmosis) and involve the blood, meninges (linings of the brain), adrenal glands, and other organs. Very young or very old people or those who have underlying immune disorders such as AIDS are at higher risk for disseminated histoplasmosis.

Symptoms

Symptoms depend on the underlying clinical syndrome:

 
• Acute asymptomatic pulmonary (lung) histoplasmosis - no symptoms  
• Acute symptomatic pulmonary histoplasmosis       o fever       o chills       o cough       o chest pain when breathing in  
• Chronic pulmonary histoplasmosis       o cough       o shortness of breath       o chest pain       o excessive sweating       o fever - may resemble symptoms of pulmonary tuberculosis and include coughing up blood (hemoptysis)  
• Disseminated histoplasmosis       o fevers       o headache       o neck stiffness       o skin lesions       o mouth sores  
• Other histoplasma syndromes       o joint pain       o skin nodules (lumps)       o rashes

Signs and tests

The diagnosis of histoplasmosis depends on the underlying condition. Tests may include analysis of the organism in sputum, lung tissue, blood, cerebrospinal fluid (CSF), or bone marrow tissue, as well as antigen tests performed on blood, urine, or CSF.

In addition, certain pathologic findings may be seen in tissue which may support the diagnosis of histoplasmosis.

Treatment
The mainstay of therapy for histoplasmosis is antifungal therapy. In the case of pulmonary histoplasmosis, this may include oral agents such as itraconazole or ketoconazole. In disseminated disease - particularly meningitis - therapy with intravenous amphotericin is used followed by long-term suppression with an oral agent such as itraconazole.

Expectations (prognosis)
Prognosis depends on the clinical syndrome - mortality is highest in disseminated histoplasmosis (up to 80% without treatment - decreased to 25% with treatment).

Complications

 
• Inflammatory syndromes involving heart lining (pericarditis)       o joints (arthritis)       o skin nodules       o rashes (erythema nodosum, erythema multiforme)  
• Fibrosing mediastinitis - scarring in the chest that may entrap structures in the chest cavity:       o lymph nodes       o heart       o great vessels       o esophagus  
• Mediastinal granuloma - enlarged chest-cavity lymph nodes which may compress structures such as esophagus and lung vessels

In individuals with weakened immune systems disseminated disease may occur and involve the meninges (meningitis)

Side Effects of medications (can be severe with amphotericin) are complications of histoplasmosis.

Calling your health care provider
Notify your medical provider if you live in an endemic area for histoplasmosis and you develop flu-like symptoms, chest pain, cough and shortness of breath. While there are many other illnesses that may have similar symptoms, you may need to be evaluated for the possibility of histoplasmosis.

Prevention
Minimize exposure to dust in contaminated environments, such as chicken coops and bat caves. Wear protective equipment such as masks if you work in these environments.

Medical Encyclopedia

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.