Myelodysplastic Syndrome
Myelodysplastic syndrome (MDS) is defined as a spectrum of rare blood disorders associated with faulty development and maturation of myeloid cells in the bone marrow without a known cause. Although it most commonly affects elderly males, its prevalence ranges from 0.22 - 13.2 per 100,000 for all age categories, genders, and ethnicities.1 The WHO classifies MDS into six types, based on the following criteria: single versus multilineage dysplasia, presence of ring sideroblasts, excess number of blast cells, and the del(5q) cytogenetic abnormality.2 About 30% of those with an initial diagnosis of myelodysplasia progress to AML, signifying a very poor prognosis. Molecular insights into acquired mutations causing MDS have led to the development of targeted therapies including p53 activators, IDH1/2 inhibitors, and spliceosome inhibitors.2
Formation
MDS is an intermediate gateway between a normal state and AML. The hematopoietic progenitor cells fail to synthesize into the myeloid lineage – erythrocytes, granulocytes, and megakaryocytes – replacing normal cells in bone marrow with abnormal blast cells. This is caused by de novo mutations and environmental exposure in the form of chemotherapy and radiotherapy. Genomic alterations in the splicing factors and DNA methylation pathways are seen in > 90% of patients, and these determine patient outcome. The SF3B1 mutation is associated with a favorable prognosis, whereas the presence of TP53, RUNX1, EZH2, ETV6, and ASXL1 indicate a probable adverse outlook.2
Diagnosis and treatment assessment
Pancytopenia and the number of blast cells in the bone marrow point towards this diagnosis, which is further confirmed by mutation analysis. A characteristic peripheral blood picture shows Pseudo-Pelger-Huet anomalies, basophilic stippling of dimorphic red cells, large agranular platelets, ringed sideroblasts (nucleated), < 20% blasts, and leukoerythroblastosis. The clinical and cytogenetic markers are aggregated to generate a score – the international prognostic scoring system revised for MDS (IPSS-R) – to guide a management plan.3
Figure 1. Example micrograph of a myelodysplastic syndrome.6
The treatment is primarily chemotherapy aimed at preventing progression to AML. Newer agents, lenalidomide and anti-thymocyte globulin, have shown to improve survival in subgroups, for example del(5q). However, the only curative treatment is a bone marrow transplant.3
Cell markers
CD45, CD34, CD117, HLA-DR, and CD123 are differentiating markers for myeloblasts. Dysplasia in immature myeloid lineages can be verified by the absence or reduced expression of CD45 and CD117, which can be evaluated by flow cytometry.4
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References
- Deborah P Lubeck, Mark Danese et al. (2016) Systematic Literature Review of the Global Incidence and Prevalence of Myelodysplastic Syndrome and Acute Myeloid Leukemia. Blood 128 (22): 5930. doi: https://doi.org/10.1182/blood.V128.22.5930.5930
- Hong, M., & He, G. (2017). The 2016 Revision to the World Health Organization Classification of Myelodysplastic Syndromes. Journal of translational internal medicine, 5(3), 139–143. https://doi.org/10.1515/jtim-2017-0002
- Eva Hellström-Lindberg, Magnus Tobiasson et al. (2020) “Myelodysplastic syndromes: moving towards personalized management”. Haematologica. 105(7): pp.1765-1779. doi: 10.3324/haematol.2020.248955.
- Germing, U., Kobbe, G et al. (2013) Myelodysplastic syndromes: diagnosis, prognosis, and treatment. Deutsches Arzteblatt international. 110(46):783–790. https://doi.org/10.3238/arztebl.2013.0783
- Laeiz Cameirao Benta, Radolfo Patussi. (2017) The Use of Flow Cytometry in Myelodysplastic Syndromes: A Review. Front. Oncol. https://doi.org/10.3389/fonc.2017.00270
- https://image.shutterstock.com/image-photo/myelodysplastic-sydrome-showing-copper-ring-600w-738912982.jpg
