Macrocytic Anemia, Thrombocytosis and Nonlobulated Megakaryocytes The 5q=Syndrome, A Distinct Entity TARIQ MAHMOOD, M.B., B.S.* WILLIAM A. ROBINSON, M.D., Ph.D. ROGER D. HAMSTRA, M.D., F.A.C.P. STEPHEN F. WALLNER, M.D. Denver, Colorado From the Divisions of Oncology and Hematology, Denver Veterans Administration Medical Center and the University of Colorado Medical Center, Denver, Colorado. This investigation was sup- ported in part by grants from the Veterans Ad- ministration 5438-01 (Dr. Mahmood) and 9205 (Dr. Wallner), National Institutes of Health, National Cancer Institute (CA23552-01) Amer- ican Cancer Society (CH-81) and the general Clinical Research Centers Program of the Divi- sion of Research Resources, NIH (RR-51). Re- quests for reprints should be addressed to Dr. Tariq Mahmood, Denver Veterans Administra- tion Medical Center, 1855 Clermont Street, Denver, Colorado 80220. Manuscript accepted January 17,1979. * Research Associate of the U.S. Veterans Administration. The clinical, hematologic and histologic characteristics of six patients with refractory anemia with deletion of the long arm of chromosome #5 are described. These patients had a distinct hematologic picture with macrocytic anemia of mild to moderate severity, normal to low leukocyte count and increased platelet count. The long arm of chromosome #5 was deleted in the majority of bone marrow meta- phases. The main cause of anemia was underproduction with de- creased erythroid precursors in the bone marrow and no increase in peripheral blood reticulocytes. Two of five patients responded transiently to the administration of androgens. In vitro evaluation of the bone marrow growth pattern in semisoljd agar culture system was performed in three patients and was found to be normal and distinct from that in patients with preleukemia. In a follow up of up to five years, no patient had changed hematologically and in none had leukemia developed. The Q-syndrome is a distinct hematologic entity and probably more common than hitherto realized. This di- agnosis may have therapeutic and prognostic implications. Refractory anemias are a heterogeneous group of disorders having in common defective red blood cell production, unresponsive to treat- ment jl-31. The term myelodysplastic syndromes has been proposed for this group of disorders because abnormalities of granulopoiesis and thrombopoiesis have been noted in addition to abnormalities in red blood cell production [4]. The finding of abnormalities in all three major hematopoietic cell lines has raised the question-does the basic defect lie in the multipotential stem cell? Such a situation exists in chronic myeloid leukemia in which the Philadelphia chromosome has been demonstr.ated in the granulocytic, erythroid, megakaryocyte and monocyte series. Recently, patients with refractory macrocytic anemia with a distinct bone marrow karyotype manifested by a partial deletion of the long arm of chromosome # 5 have been described and the condition termed the 5q-syndrome [5,6]. This would have fit into the broad category of the myelodysplastic syndrome [7]. This was one of the first demon- strations of a specific karyotypic abnormality occurring in this broad disease category. In the past three years we had the opportunity to study six patients with the same karyotypic abnormality (partial deletion of the long arm of chromosome #5) at the University of Colorado Medical Center. These patients are the subject of this report. We describe here the clinical manifestations, hematologic picture, response to therapy and the in vitro bone marrow growth characteristics of these patients. 946 June 197s The AmericanJournalof Medicine Volume 66