USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

Which condition is primarily associated with a decrease in Eosinophils?

1. SLE

2. Cushing Syndrome

3. Chronic Kidney Disease

4. Corticosteroid-induced Neutrophilia

The correct answer is: Cushing Syndrome

Cushing Syndrome is primarily associated with a decrease in Eosinophils due to the effects of excessive cortisol production on the immune system. In this condition, the elevated levels of cortisol lead to lymphocyte apoptosis and a reduced count of eosinophils, which are a type of white blood cell involved in allergic responses and fighting parasitic infections. This immune dysregulation is a hallmark of Cushing Syndrome, as the high cortisol levels contribute to changes in the distribution and numbers of various leukocyte populations. In contrast, conditions like SLE (Systemic Lupus Erythematosus) may actually promote eosinophilia due to immune activation and inflammation. Chronic Kidney Disease can have varying effects on eosinophil levels depending on the underlying causes and treatments, and corticosteroid use generally leads to increased neutrophils rather than a direct, consistent decrease in eosinophils. Therefore, the association of decreased eosinophils is most directly and characteristically linked to Cushing Syndrome.