Histoplasmosis

Introduction. 

Histoplasmosis is a pulmonary or systemic fungal infection common in the midwestern US. It is common in caves (spelunkers' disease) and other areas with bat or bird droppings.  Most people who inhale the mold spores are asymptomatic, but 5% show clinical signs of pneumonia. In a few patients, this may progress to systemic disease, particularly in immunosuppressed individuals (AIDS). Histoplasma capsulatum, the pathogen, is able to survive and replicate within macrophages. 

Summary

• Cause: Histoplasma capsulatum
• Microscopy: Dimorphic fungus with characteristic macroconidia; pathogenic yeast form
• Transmission: Respiratory
• Symptoms: pneumonia-like (5% of infected)
• Complications: progressive disease in AIDS
• Pathogenesis: intracellular growth within macrophages; immunopathogenesis
• Treatment: Amphothericin B