A 55-year-old male patient with pure red cell aplasia was reported. This patient's disease had several interesting features. Firstly, his moderate anemia became very severe immediately after removal of his thymoma which had been discovered incidentally 2 months before surgery. Secondary, he had many immunological abnormalities; false positive STS, positive LE cell phenomenon, positive antinuclear antibody, negative tuberculin reaction and inability to react to typhoid vaccine. Thirdly, reticulocytes began to appear in the peripheral blood after splenectomy, while corticostoroids and anabolic steroids were totally ineffective. Fourthly, his plasma had a high erythropoietic activity and no neutralizing activity to erythropoietin or inhibiting activity to normal erythropoiesis could be demonstrated in it.
