This article focuses on the features of myelodysplastic syndromes (MDS) associated with isolated del(5q) as they relate to pathology.
MDS with isolated del(5q) is one of a group of clonal disorders of myeloid stem cells that are characterized by ineffective hematopoiesis, manifested in morphologic dysplasia of hematopoietic precursors and characterized by one or more peripheral blood cytopenias. In patients with MDS with isolated del(5q), the morphologic dysplasia is most evident as an increase in the number of small, hypolobated megakaryocytes, as seen in the following image.
Normocellular bone marrow with increased numbers of small, hypolobated megakaryocytes. In this case, granulocytes and erythroid precursors show normal maturation (bone marrow aspirate, Wright-Giemsa, ×1000).
See Myelodysplastic Syndromes: Classification, Features, Diagnosis, and Treatment Options, a Critical Images slideshow, to help identify, classify, work up, and treat these disorders.
Patients typically present with marked macrocytic anemia with or without other cytopenias and a normal or increased platelet count in the peripheral blood. This form of MDS is defined in part by the presence of deletion in the long arm of chromosome 5 (del(5q)) as the sole cytogenetic abnormality. In cases of MDS with isolated del(5q), there are less than 5% blasts in the bone marrow and less than 1% blasts in the peripheral blood. In addition, Auer rods are not present.
Progression to acute myeloid leukemia (AML) is less common in MDS with isolated del(5q) than in other forms of MDS.
Del(5q) is one of the most frequent abnormalities identified in MDS,
including many cases of MDS associated with previous chemotherapy or with other cytogenetic abnormalities.
In cases in which the patient has received previous chemotherapy, MDS in which del(5q) is the sole abnormality should be classified as a therapy-associated myelodysplastic syndrome (t-MDS). The prognosis for patients with t-MDS is not as favorable as the prognosis for patients with MDS with isolated del(5q). If additional cytogenetic abnormalities are present and the patient has no history of chemotherapy, the disease should be classified on the basis of morphologic parameters.
As with other forms of MDS, MDS with isolated del(5q) is predominantly a disease of elderly persons; the median age of patients at the time of presentation is between 65 and 70 years. As described in van den Berghe et al’s original series
and as defined by the World Health Organization (WHO) classification of tumors of hematopoietic and lymphoid tissues,
MDS with isolated del(5q) is more common in women.
See also Pediatric Myelodysplastic Syndromes Pathology, Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Features, Pathology of Therapy-Related Myeloid Neoplasms, Pathology of Other Myeloid Related Precursor Neoplasms, and Pathology of Acute Myeloid Leukemia Not Otherwise Categorized.