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Myelodysplastic Syndromes – Classification, Signs And Symptoms

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Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are a group of disorders due to clonal proliferation of an abnormal stem cell, resulting in quantitative and qualitative hemopoietic abnormalities, with varying degrees of cytopenia in one or more cell lines, as a result of a marrow replacement by the malignant clone. Bone marrow remains normo or even hypercellular.

MDS are disorders at the border between refractory anemia and leukemia, they arise usually after 50 years of age and their incidence has increased during the last years. By etiology,  they are classified in primary MDS, in which genetic mutations seem to play a major role and secondary MDS – due to exposure to alkilating agents and radiation.

The pathophysiologic mechanism is defective maturation coupled with enhanced proliferation of precursor cells.The indolent course of these diseases is due to coexistence of normal and abnormal (clonal) hemopoiesis. When maturation is totally blocked, the disease merges into acute leukemia.

Diagnosis is based on the presence of dysplasia in the blood and marrow cells.

Myelodysplastic Syndromes Classification

FAB classification (French-American-British):

Refractory anemia (RA)

  • <1% blast cellsin the blood , <5% blast cells in the marrow and <15% ringed sideroblasts;
  • usually assocated with neutropenia and/or thrombocytopenia (“refractory cytopenia”);
  • in the marrow: diserythropoiesis, dismegakariopoiesis with or without disgranulopoiesis.

Refractory anemia with ringed sideroblasts (RARS)

  • presence of 1% blast cells in the blood, <5% blast cells in the marrow and <15% ringed sideroblasts (characteristic for this type);
  • may be classified in:

-“pure” sideroblastic anemia  – characterized by diserythropoiesis and rare transformation in acute leukemia;

-RARS – characterized by diserythropoiesis, disgranulopoiesis, and/or dismegakariopoiesis, evolution into acute leukemia common.

Myelodysplastic Syndromes

Myelodysplastic Syndromes

Refractory anemia with excess blasts (RAEB)

  • presece of <5% blast cells in blood;
  • marrow blasts 5 to 19% with a variable percent of ringed sideroblasts;
  • dominant morphological feature is disgranulopoiesis;
  • high rate of leukemic transformation.

Refractory anemia with excess blasts in transition (RAEBT)

  • transition form between RAEB and acute leukemia;
  • 5-29% blasts in blood, marrow blasts: 20-29%;
  • Auer rods may be present.

Chronic myelomonocytic leukemia (CMML)

  • <5% blasts and monocytes >1000 ul in blood(absolute monocytosis with leukocytosis is definitory for this entity);
  • in the marrow: immature myeloid and erythroid precursor cells;
  • regarding its clinical and laboratory features (hepatosplenomegaly, leukocytosis, occasionally myelofibrosis) this entity seems t be related more closely to the myeloproliferative disorders. Its classificaton in the MDS group is disputable.

Myelodspalstic Syndrome’s Signs And Symptoms

A few years before developing a MDS, patients may present macrocytic anemia and a mild thrombocytopenia or neutropenia but with no evidence of megaloblastic anemia. This anemia usually results in fatigue and malaise. In patients with cardiac problems may occur signs of chronic heart failure. Due to the low platelet count, patients may have nose and gum bleeding, petechiae and ecchymoses. Moreover, neutropenia may cause all sorts of bacterial and fungal infections associated with symptoms such as fever, dysuria, cough or even shock.

Myelodysplastic Syndromes Symptoms

Myelodysplastic Syndromes Symptoms

After being diagnosed, patients with MDS most often manifest their severe thrombocytopenia as epistaxis, gum bleeding, petechiae and echymoses. Also may occur blood in stools and urine. The severe anemia is represented by the pallor of the skin, fatigue, tachycardia or even heart failure in those cases where underlying heart problems were present. Neutropenia causes fever and infections; the most common infections are pneumonias and urinal tract infections.