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Histoplasmosis - Causes, Symptoms and Treatment

What is Histoplasmosis?

Also called Ohio Valley disease, Central Mississippi Valley disease, Appalachian Mountain disease, and Darling's disease, histoplasmosis is a fungal infection caused by Histoplasma capsulatum. In the United States, it occurs in three forms: primary acute histoplasmosis, progressive disseminated histoplasmosis (acute disseminated or chronic disseminated disease), and chronic pulmonary (cavitary) histoplasmosis, which produces cavitations in the lung similar to those in pulmonary tuberculosis. A fourth form, African histoplasmosis, is caused by the fungus Histoplasma capsulatum var. duboisii.

Histoplasmosis occurs worldwide, especially in the temperate areas of Asia, Africa, Europe, and North and South America. In the United States, it is most prevalent in the central and eastern states, especially in the Mississippi and Ohio river valleys. Probably because of occupational exposure, histoplasmosis is more common in men. Fatal disseminated disease is more common in infants and elderly men.

The prognosis varies with each form.

The primary acute disease is benign; the progressive disseminated disease is fatal in about 90% of patients; without proper chemotherapy, chronic pulmonary histoplasmosis is fatal in 50% of patients within 5 years.

What are the Causes of Histoplasmosis?

H. capsulatum is found in the feces of birds and bats or in soil contaminated by their feces, such as that near roosts, chicken coops, barns, and caves and under bridges. Transmission is through inhalation of H. capsulatum or H. duboisii spores or through the invasion of spores after minor skin trauma. The incubation period is 5 to 18 days, although chronic pulmonary histoplasmosis may progress slowly for many years.

What are the Signs and Symptoms of Histoplasmosis?

Symptoms vary with each form of this disease:

. Primary acute histoplasmosis may be asymptomatic or cause symptoms of a mild respiratory illness similar to those that accompany a severe cold or influenza. Typical symptoms include fever, malaise, headache, myalgia, anorexia, cough, and chest pain.

. Progressive disseminated histoplasmosis causes hepatosplenomegaly, general lymphadenopathy, anorexia, weight loss, fever and, possibly, ulceration of the tongue, palate, epiglottis, and larynx with resulting pain, hoarseness, and dysphagia. It may also cause endocarditis, meningitis, pericarditis, and adrenal insufficiency .

. Chronic pulmonary histoplasmosis mimics pulmonary tuberculosis and causes a productive cough, dyspnea, and occasional hemoptysis. Eventually, it produces weight loss, extreme weakness, breathlessness, and cyanosis.

. African histoplasmosis produces lymphadenopathy, lesions of the skull and long bones, visceral involvement without pulmonary lesions, cutaneons nodules, papules, and ulcers.

Diagnosis for Histoplasmosis

A history of exposure to contaminated soil in an endemic area, miliary calcification in the lungs or spleen, and a positive histoplasmin skin test indicate exposure to H. capsulatum. Rising complement fixation and agglutination titers (more than 1:32) strongly suggest the diagnosis. A urinary antigen test for histoplasmosis is now used for diagnosis.

The diagnosis of histoplasmosis requires morphologic examination of a tissue biopsy and culture of H. capsulatum from sputum in acute primary and chronic pulmonary histoplasmosis and from bone marrow, lymph nodes, blood, and infection sites in disseminated histoplasmosis. Cultures take several weeks to grow these organisms.

A faster diagnosis is possible with stained biopsies. Findings must rule out tuberculosis and other diseases that produce similar symptoms. The diagnosis of histoplasmosis caused by H. duboisii necessitates examination of a tissue biopsy and culture of the affected site.

Treatment for Histoplasmosis

Histoplasmosis treatment consists of antifungal therapy, surgery, and supportive care. Antifungal therapy is most important. Except for asymptomatic primary acute histoplasmosis (which resolves spontaneously) and the African form, histoplasmosis requires high-dose or long-term (IO-week) therapy with amphotericin B or fluconazole. For a patient who also has acquired immunodeficiency syndrome, lifelong therapy with fluconazole is indicated.

Supportive care usually includes oxygen for respiratory distress, glucocorticoids for adrenal insufficiency, and parenteral fluids for dysphagia due to oral or laryngeal ulcerations.

Histoplasmosis doesn't require the patient to be isolated.

Special Considerations and Prevention Tips for Histoplasmosis

Below are some of the tips which will help you control the diseases and also prevent it from getting more serious:

  • Administer medications, and teach patients about possible adverse effects. Because amphotericin B may cause chills, fever, nausea, and vomiting, give appropriate antipyretics and antiemetics.
  • Patients with chronic pulmonary or disseminated histoplasmosis also need psychological support because of long-term hospitalization.
  • As needed, refer the patient to a social worker or an occupational therapist. Help parents of children with this disease arrange for a visiting teacher.
  • Teach people in endemic areas to watch for early signs of this infection and to seek treatment promptly. Instruct people who risk occupational exposure to contaminated soil to wear face masks.

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