Macrocytic anemia, thrombocytosis and nonlobulated megakaryocytes: the 5q-syndrome, a distinct entity.

The clinical, hematologic and histologic characteristics of six patients with refractory anemia with deletion of the long arm of chromosome No. 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 No. 5 was deleted in the majority of bone marrow metaphases. The main cause of anemia was underproduction with decreased 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 semisolid 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 5q-syndrome is a distinct hematologic entity and probably more common than hitherto realized. This diagnosis may have therapeutic and prognostic implications.