Molecular pathogenesis of the 5q- syndrome

© 2009 by Informa Healthcare USA, Inc. The 5q- syndrome was first described as a “distinct haematological disorder with deletion of long arm of no. 5 chromosome” by Herman van Den Berghe and his colleagues in Leuven, Belgium, in 1974 (1). The syndrome was described in more detail in a subsequent report in 1975 by Gerard Sokal and colleagues, also in Leuven (2). The principal features described in these early reports were a moderate-to-severe macrocytic anemia, with slight leukopenia but normal or elevated platelet count. The bone marrow showed a depressed erythroid series with an occasional excess of myeloblasts. Most of the megakaryocytes had a nonlobulated nucleus. It was recognized early that patients with the 5q- syndrome had a female preponderance, and a good prognosis with a low transformation rate to acute myeloid leukemia (AML) (3). The 5q- syndrome quickly became linked with the myelodysplastic syndromes (MDS). The World Health Organization (WHO) definition of the 5q- syndrome (see chap. 9) is part of the WHO’s MDS classification and includes a more stringent requirement for the patient to be in the refractory anemia (RA) subgroup of MDS, excluding patients with over 5% blasts. Those patients who fall outside the WHO definition of the 5q- syndrome may have some of the hematological features of the 5q- syndrome, but nevertheless do not share its good prognosis (4).