What is histoplasmosis?

From the Guidelines

Histoplasmosis treatment should prioritize itraconazole (200mg twice daily) for mild-to-moderate disease, while severe or disseminated infections require initial liposomal amphotericin B (3.0 mg/kg daily) followed by itraconazole for a total of at least 12 months, as recommended by the Infectious Diseases Society of America 1.

Disease Overview

Histoplasmosis is a fungal infection caused by Histoplasma capsulatum, primarily affecting the lungs but capable of disseminating throughout the body. Most infections occur through inhalation of fungal spores found in soil contaminated with bird or bat droppings, particularly in the Ohio and Mississippi River valleys.

Diagnosis and Treatment

Diagnosis involves antigen testing, serology, culture, or histopathology. Treatment depends on disease severity:

• Mild cases often resolve without therapy
• Moderate to severe infections require antifungal medications
• Itraconazole is the primary treatment for mild-to-moderate disease
• Severe or disseminated infections typically require initial amphotericin B followed by itraconazole for a total of at least 12 months Some key points to consider:
• Liposomal amphotericin B is preferred for severe disease due to reduced toxicity 1
• Long-term suppressive therapy with itraconazole may be necessary for immunocompromised patients 1
• Blood levels of itraconazole should be obtained to ensure adequate drug exposure 1
• Antigen levels should be measured during therapy and for 12 months after therapy is ended to monitor for relapse 1

Prevention

Prevention focuses on avoiding exposure to contaminated soil and dust, particularly during construction or excavation in endemic areas, with special precautions recommended for immunocompromised individuals. Some key considerations:

• Active histoplasmosis during the past 2 years may be a basis for itraconazole prophylaxis during immunosuppression 1
• The appropriate duration of prophylaxis is unknown 1
• Antiretroviral therapy should not be withheld on the basis of concern about the possible development of immune reconstitution inflammatory syndrome in patients with AIDS 1

From the Research

Overview of Histoplasmosis

• Histoplasmosis is a disease caused by the dimorphic fungus Histoplasma capsulatum, with a wide clinical spectrum in terms of disease cadence, onset, distribution, and severity 2.
• The disease has become a national concern due to increasing numbers of travelers and immunocompromised patients 2.
• Histoplasmosis is the most common endemic mycosis in North America, Central America, and many countries of South America, and also occurs in other parts of the world 3.

Diagnosis and Management

• A multipronged approach is recommended for diagnosis, and manifestations that are always treated include moderate to severe acute pulmonary histoplasmosis, disseminated disease, and histoplasmosis in immunocompromised individuals 2.
• Amphotericin B is the drug of choice for moderate to severe and disseminated presentations, whereas itraconazole is appropriate for mild disease and as step-down therapy 2, 3.
• Posaconazole may be a useful salvage treatment option for histoplasmosis involving a variety of infected tissues and organs 4.
• Fluconazole can be used for chronic suppressive therapy of histoplasmosis in patients who cannot take itraconazole due to drug interactions, malabsorption, or side effects 5, 6.

Treatment Outcomes

• Treatment with posaconazole has shown successful clinical outcomes with significant clinical improvements noted during the first month of therapy 4.
• Fluconazole has been shown to be a safe and moderately effective induction therapy for mild or moderately severe disseminated histoplasmosis in patients with AIDS 6.
• However, fluconazole 400 mg daily is less effective than itraconazole 200 to 400 mg daily or amphotericin B 50 mg given weekly as maintenance therapy to prevent relapse 6.