Abnormalities in Chromosomes 5 and 7 in Myelodysplastic Syndrome and Acute Myeloid Leukemia

Chromosomes 5 and 7 are large chromosomes that contain close to 1,000 genes each. Deletions of the long arms or loss of the entire chromosome (monosomy) are common defects in myeloid disorders, particularly MDS and AML. Loss of material from either chromosome 5 or 7 results in haploinsufficiency of multiple genes, with some implicated in leukemogenesis. Abnormalities of one or both occur in up to 15% of MDS and AML cases and co-segregate in half of these. Generally, these chromosomal abnormalities are harbingers of adverse risk in both myeloid disorders. A notable exception is del(5q) in 5q- syndrome, a subtype of MDS. In this review, we describe the pathogenesis and genetic consequences of deletions in chromosomes 5 and 7. Furthermore, we provide an overview of current testing methodologies used in the assessment of these chromosomal defects in hematological malignancies and describe the disease associations and prognostic implications of aberrations in chromosomes 5 and 7 in both MDS and AML.