Myelodysplastic syndrome (MDS) with isolated 5q- chromosomal abnormality and less than 5% bone marrow blasts, according to WHO classification, represents a separate MDS subgroup. Most such patients have distinct clinical and pathological features and fit into a diagnosis of 5q- syndrome with isolated 5q- deletion, hypo-proliferative anemia, normal or increased platelet count, low bone marrow blasts (BM), dysplastic megakaryocytes and long survival.
Among the most common cytogenetic abnormalities identified in patients with MDS are interstitial deletions involving the long arm of chromosome 5 in frequencies ranging from 14 to 31%. Patients with the isolated 5q- chromosomal abnormality are considered to have very good prognosis and survival often longer than 100 months.