This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Intravenous immunoglobulin therapy is effective in some patients with which of the conditions? 
Select and explain. 
A. Pure red cell aplasia, B. Myelodysplasia, C. PNH, D. G6PD deficiency
A: Pure red cell aplasia
Answer: A: Pure red cell aplasia 
Explanation: Red cell aplasia is treated with combination of erythrocyte transfusions and iron chelation. For persistent B19 parvovirus infection, almost all patients respond to intravenous immunoglobulin therapy. Ref: Harrisons Principles of Internal Medicine, 18th Edition, Page 895