Pure red cell aplasia

Pure red cell aplasia is a rare form of anemia caused when the bone marrow stops producing red blood cells, but produces white blood cells normally. It's usually a symptom of another underlying disorder, but can be congenital or idiopathic.
Several other conditions can cause red cell aplasia, including:
*Autoimmune conditions
*A Thymoma
*Infections, including HIV, Herpes, and Hepatitis
*Drugs, such as erythropoietin
In addition to an infusion of red blood cells, the condition usually responds well to ciclosporin.
Pure red cell aplasia at Wikipedia