Pure red cell aplasia (PRCA) was first described by Kaznelson (1922) as an anemia due to an almost complete cessation of erythropoiesis, but without leukopenia or thrombocytopenia. This condition usually can be clearly distinguished from aplastic anemia in which low blood white cell and platelet concentrations accompany the anemia (Van Der Weyden and Firkin, 1972). In PRCA the bone marrow has an isolated absence of erythroblasts with normal granulocytopoiesis and megakaryocytopoiesis (DiGiacomo et al., 1966; Jacobs et al., 1959), whereas in aplastic anemia all three hematopoietic lineages are markedly reduced (Van Der Weyden and Firkin, 1972). In children PRCA has been called “chronic (congenital) hypoplastic anemia,” the Diamond-Blackfan anemia, or erythrogenesis imperfecta (Diamond and Blackfan, 1938; Gasser, 1957; Tsai and Levin, 1957). In adults it has been termed isolated aplastic anemia, aplastic crisis, erythroblastopenia, erythrophthisis, chronic erythrocytic hypoplasia, red cell aplastic anemia, or red cell agenesis (Gasser, 1957; Tsai and Levin, 1957). Although these cases could represent a variety of pathogenetic mechanisms they all have in common an isolated absence of marrow erythroblasts and are now considered together as cases of PRCA.