Microcytosis is a characteristic laboratory feature for both iron deficiency anemia and thalassemia. It is also infrequently seen in "anemia of chronic disease" that accompanies a spectrum of chronic conditions including rheumatoid arthritis, polymyalgia rheumatica, diabetes mellitus, connective tissue disease, and protracted infection. In addition, there is a well established but pathogenetically obscure association of microcytosis with Hodgkin's lymphoma, Castleman's disease, and renal cell carcinoma. In the current study, we show that microcytosis is a frequent laboratory feature in agnogenic myeloid metaplasia and investigate its clinical relevance in the particular setting., (c) 2005 Elsevier Ltd. All rights reserved.