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

What characterizes Pure Red Cell Aplasia (PRCA) regarding marrow failure?

1. Inhibition of granulopoiesis and thrombopoiesis

2. Increased production of erythroid elements

3. Development of monoclonal antibodies

4. Association with Thymoma and parvovirus B19 infection

The correct answer is: Inhibition of granulopoiesis and thrombopoiesis

The correct characterization of Pure Red Cell Aplasia (PRCA) is its association with conditions that specifically target and inhibit erythropoiesis, leading to a marked reduction in red blood cell production while leaving other hematopoietic lineages (like granulocytes and platelets) relatively unaffected. PRCA primarily involves a lack of functional erythroid progenitor cells in the bone marrow, which results in anemia due to the inadequate production of red blood cells. Instead of seeing an increase in the production of erythroid elements, there is a failure of erythrocyte formation. Additionally, while some conditions associated with PRCA may involve various autoimmune aspects or infections, the hallmark is specifically the suppression of the red cell lineage rather than broad marrow failure affecting other cell lines like granulocytes or megakaryocytes. In the context of the other options, while there could be situations where PRCA overlaps with antibody-mediated processes or associations with conditions like Thymoma and parvovirus B19, the defining feature is primarily the inhibition of erythropoiesis leading to red cell aplasia. Therefore, the correct answer focuses on the specific impairment of red blood cell production as the direct cause of the disorder.