What is Myelodysplastic Syndrome (MDS)? MDS is a diverse group of syndromes which are characterized by the atypical (dysplastic) or ineffective production of blood cells. These syndromes are considered to be malignant stem cell disorders. Stem cells are immature cells in the bone marrow that gradually mature to form the various components of blood. There are three main cell lines which form blood: Red blood cells (also known as erythrocytes), which carry inhaled oxygen from the lungs to other organs and carry carbon dioxide from the organs to the lungs to be exhaled. Platelets (also known as thrombocytes), which form clots. White blood cells (also known as leukocytes), which are comprised of granulocytes, lymphocytes, and monocytes, each of which has a different role in the immune system. Lymphocytes are made up of B and T lymphocytes. In MDS, the stem cells do not mature properly and ... read more on Myelodysplastic Syndromes (MDS): The Basics