Chromosome 5q deletion syndrome is an acquired, hematological disorder characterized by loss of part of the long arm (q arm, band 5q33.1) of human chromosome 5 in bone marrow myelocyte cells.

The 5q-syndrome is characterized by macrocytic anemia, often a moderate thrombocytosis, erythroblastopenia, megakaryocyte hyperplasia with nuclear hypolobation, and an isolated interstitial deletion of chromosome 5.

[3][4] Haploinsufficiency of RPS14 plays a central role, and contributes to the anemia via both p53-dependent and p53-independent tumor suppressor effects.

[4] Other genes at this region include miR-145 and miR-146a, whose deletion is associated with the megakaryocytic dysplasia and thrombocytosis seen in 5q- syndrome;[5] SPARC, which has antiproliferative and antiangiogenic effects; and the candidate tumor suppressors EGR1, CTNNA1, and CDC25C.

[6] Lenalidomide has activity in 5q- syndrome[7] and is FDA approved for red blood cell (RBC) transfusion-dependent anemia due to low or intermediate-1 (int-1) risk myelodysplastic syndrome (MDS) associated with chromosome 5q deletion with or without additional cytogenetic abnormalities.