Myelodysplastic syndromes (MDS) are a heterogeneous group of myeloid neoplasms characterized by the presence of cytopenias, ineffective hematopoiesis and frequent transformation into secondary acute myeloid leukemia (secAML). Recent genomic studies provide unprecedented insight into the molecular landscape of clonal proliferation in MDS. Genetic diversity of both MDS and secAML subclones cannot be defined by a single somatic mutation. Mutations of the founding clone may survive over implemented chemotherapy and allogenic hematopoietic cell transplantation (alloHCT), but new subclonal mutations may also appear. Next generation sequencing (NGS) makes it possible to define the mutational profile of disease subclones during the treatment course and has a potential in pre- and post-alloHCT monitoring. Understanding the molecular pathophysiology of MDS may soon allow for monitoring the course of disease and personalized treatment depending on the mutational landscape. In the present paper we report, for the first time in MDS, ASXL1 c.1945G>T, TET2 c.4044+2dupT and c.4076G>T sequence variants. Moreover, we detected RUNX1 c.509-2A>C and SF3B1 c.1874G>T sequence variants. Furthermore, we verify the clinical utility of NGS and pyrosequencing in MDS and secAML.