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

Corticosteroids are known to have significant effects on the immune system and the distribution of various white blood cells, including eosinophils. In conditions characterized by elevated cortisol levels, such as Cushing Syndrome, corticosteroids lead to a redistribution of eosinophils. In Cushing Syndrome, the increased levels of cortisol result in the sequestration or trapping of eosinophils, primarily in the lymph nodes. This phenomenon occurs because corticosteroids enhance lymphocyte apoptosis and alter the migration patterns of these immune cells. As a result, fewer eosinophils circulate in the blood, leading to a relative eosinopenia, while a higher concentration of eosinophils can be found in the lymphatic tissues. This contrasts with the other conditions listed, where the mechanisms of disease do not typically involve the direct effects of corticosteroids on eosinophil distribution. For instance, Multiple Myeloma is primarily a malignant proliferation of plasma cells; Systemic Lupus Erythematosus (SLE) is an autoimmune condition that has a different immunological profile; and Polycythemia Vera is characterized by increased red blood cell production rather than the effects of corticosteroids on leukocyte distribution. Therefore, the scenario that best