American Board of Internal Medicine (ABIM) Certification Practice Exam

What is considered a significant risk factor for developing Histoplasmosis?

1. Exposure to soil

2. CD4 cell count less than 200/µL

3. Living in a dry climate

4. Traveling internationally

The correct answer is: CD4 cell count less than 200/µL

A significant risk factor for developing histoplasmosis is a CD4 cell count of less than 200/µL. Histoplasmosis is a fungal infection caused by inhaling the spores of the fungus Histoplasma capsulatum, which is commonly found in soil, especially in areas with bird or bat droppings. In immunocompetent individuals, exposure might not lead to significant disease. However, individuals with advanced immunosuppression, such as those with HIV/AIDS and a CD4 count below 200 cells/µL, are at a much higher risk of developing severe forms of histoplasmosis. When the immune system is compromised, the body is less able to fight off infections, making opportunistic infections like histoplasmosis more likely to occur. Therefore, the risk of contracting histoplasmosis and experiencing severe symptoms increases significantly with a low CD4 count. While exposure to soil does pose a risk for histoplasmosis due to the presence of the fungus in certain environments, it is not an absolute predictor of the disease, especially in individuals with intact immune systems. Living in a dry climate does not promote the growth of Histoplasma, which favors more humid conditions. Finally, traveling internationally may increase exposure to various pathogens, but