Erythroid dysplasia is a condition in which immature red blood cells (erythroid cells) in the bone marrow are abnormal in size and/or number. Erythroid dysplasia may be caused by vitamin deficiency or chemotherapy, or it may be a sign of refractory anemia, which is a myelodysplastic syndrome. Also called erythrodysplasia. Erythroid dysplasia is a condition in which immature red blood cells (erythroid cells) in the bone marrow are abnormal in size and/or number. Erythroid dysplasia may be caused by vitamin deficiency or chemotherapy, or it may be a sign of refractory anemia, which is a myelodysplastic syndrome. Also called erythrodysplasia. This article incorporates public domain material from the U.S. National Cancer Institute document 'Dictionary of Cancer Terms'.