Myelodysplastic syndrome is currently considered to be a hematopoietic dysfunction caused by abnormal proliferation and differentiation of hematopoietic stem cells. The main manifestations are a decrease in peripheral blood whole blood cells and a proliferation of myeloid cells with morphological abnormalities in mature and naive cells i.e. pathological hematopoiesis. Some patients transform into acute leukemia after a certain period of MDS; some die due to infection, bleeding or other causes and never transform into acute leukemia during the course of the disease.
Diagnosis
I. At least two lines of bone marrow show pathological hematopoiesis.
The peripheral blood may be reduced in lineage 1, lineage 2 or whole blood cells, occasionally leukocytes may be increased, and nucleated red blood cells or giant red blood cells or other pathological hematopoiesis may be seen.
Excluding other diseases causing pathological hematopoiesis, such as erythroleukemia, M2b acute non-lymphoblastic leukemia, myelofibrosis, chronic granulocytic leukemia, primary thrombocytopenic purpura, and megaloblastic anemia.
The FAB panel classified MDS into five types with the following criteria.
I. Refractory anemia (RA)
Blood picture: anemia, occasionally patients with granulocytopenia and thrombocytopenia without anemia. Reticulocytes are reduced. Erythrocytes and granulocytes with pathological hematopoiesis. Primocytes absent or <1%.
Bone marrow: active or markedly active hyperplasia. The red lineage is hyperplastic and has pathological hematopoiesis. Rarely, granulocytes and megakaryocytes are pathologically hematopoietic. Primitive cells <5%.
II. Refractory anemia with cyclic iron granulocytes (RAS)
The number of ringed iron granulocytes in the bone marrow is 15% or more of all nucleated cells in the bone marrow, otherwise the same as RA.
III. Refractory anemia with primitive cellular increase (RAEB)
Blood picture: 2 lines or whole blood cell reduction, mostly granulocytic pathological hematopoiesis, primitive cells <5%.
Bone marrow: markedly active hyperplasia, both granulocytic and erythrocytic lineages are hyperplastic. 3 lineages have pathological hematopoiesis, primitive cell type I + II is 5% to 20%.
Chronic granulocytic mononuclear leukemia (CMML)
Blood picture: absolute value of monocytes >1×109/L. Granulocytes are also increased and have granulocytopenia or Pelger-Huet abnormalities. Primitive cells <5%.
Bone marrow: same as RAEB, primitive cells 5%-20%.
V. RAEB in transformation (RAEB-T)
Blood and bone marrow resemble RAEB, but with any of the following three conditions.
①75% primitive cells in the blood;
②Bone marrow with 20-30% primitive cells;
(3) Naïve cells with Auer vesicles.
Treatment
I. Supportive treatment
RA and RA-S often have increased iron load due to repeated blood transfusion. In the presence of bleeding and infection, platelets may be transfused and antibiotics applied. Prophylactic transfusion of granulocytes and platelets has no clear efficacy in patients with MDS.
II. Vitamin therapy
Some RAS are effective for vitamin B6 treatment, 200-500mg/day IV, which can increase reticulocytes and decrease transfusion.
Adrenocorticosteroids
In about 10-15% of MDS patients, the peripheral blood count increases significantly after applying adrenocorticotropic hormone therapy, but the side effects brought by corticotropic hormone therapy, such as easy infection and elevated blood sugar, should not be ignored.
IV. Differentiation inducers
Some cells in malignant clones of MDS patients still retain differentiation potential, and some drugs can induce differentiation of tumor cells. Currently, 1,25 dihydroxyvitamins and 13-cis retinoic acid are commonly used, as well as small doses of cytarabine have differentiation-inducing effects on myeloid leukemia.
V. Androgens
Contrilon and danazol are the most commonly used male hormones.
VI. Combination chemotherapy
In most cases of MDS, conventional anti-leukemia therapy is not beneficial; MDS has low tolerance to chemotherapy, poor treatment efficacy, and short remission periods even when remission is achieved. If the patient is less than 50 years old and in good clinical status for RAEB-T, conventional chemotherapy may be used as appropriate.
VII. Bone marrow transplantation
Allogeneic bone marrow transplantation (allogeneic and hemiphasic bone marrow transplantation) can be considered when the patient is younger than 50 years old and is in RAEB or RAEB-T with a suitable donor and medical conditions permitting.