Myelodysplastic syndromes (MDS) are a group of acquired clonal disorders originating in hematopoietic stem/progenitor cells characterized by dysplastic hyperplasia and ineffective hematopoiesis. It is characterized by cytopenia of one or more lines in peripheral blood, hyperplasia of the bone marrow, and morphological abnormalities, including pathological erythroids, pathological granules, or pathological platelet production. MDS is a multi-stage pathological process involving polygenes, and stem cell gene abnormalities, hematopoietic microenvironment changes and immune mechanism defects all play important roles in the pathogenesis.
Myelodysplastic syndrome MDS is called "pre-leukemia" by patients with blood diseases, indicating that this disease is an early manifestation of leukemia, the overall MDS leukemia conversion rate is about 30%, it has two common characteristics: bone marrow can not provide enough normal cells for blood circulation (ineffective hematopoiesis); All subtypes of MDS present with pathological hematopoiesis (malformed cells) in the bone marrow.
Most patients have an insidious onset, more common in men and older men, and about 70% of cases are over 50 years old. It is rare in children, but in recent years there has been an increase in adolescent morbidity. The initial symptoms of MDS lack specificity, and some patients may have no obvious symptoms. Most patients have dizziness, fatigue, epigastric discomfort, and osteoarthralgia. Most begin with anemia and may be the first symptom of presentation and last for months to years. About 20%~60% of cases are accompanied by bleeding tendency in the course of the disease, the degree is different, and there are skin petechiae. Bleeding gums, epistaxis. Severe cases may have gastrointestinal or cerebral hemorrhage. Bleeding is associated with low platelets, and some patients have defects in platelet function.
About half of the patients have fever during the course of the disease, fever is associated with infection, the fever pattern is variable, respiratory infections are the most, and the rest have sepsis, perianal and perineal infections. In cases that do not transform into acute leukemia, infection and/or bleeding are the main causes of death. The liver and spleen may have moderate or mild enlargement, and lymphadenopathy in 1/3 of cases, which is painless. Individual patients have sternal tenderness.
Peripheral pancytopenia, the degree of which varies by type. Most patients have significant or hyperactive bone marrow hyperplasia, and a few are normal or reduced. Abnormal cell morphology reflects pathological hematopoiesis in MDS. Childish cells at all stages of the erythroid system are often accompanied by megaloblastic changes, imbalance in the maturation of the nuclear plasma, large or ovulate size of red blood cells, basophilic dots, nuclear fragmentation. Granules can see a higher proportion of blasts than normal. Granulocyte intraplasmic granules are coarse or reduced, and nuclear lobes are too many or too few. Megakaryocytes can be abnormal in number and quality, most megakaryocytes are increased, and the detection of small megakaryocytes is one of the supporting diagnostic indicators of MDS. Platelets are large in volume and granules in small size.
The FAB collaboration group mainly divided MDS into 5 types according to the proportion of blasts in peripheral blood and bone marrow of MDS patients, morphological changes and the number of monocytes: refractory anemia (RA), RA with ringed sideroblasts (RAS), refractory anemia with excess blasts (RAEB), Refractory anemia with RAEB in transformation (RAEB-t), chronic myelomonocytic leukemia (CMML).
There is no satisfactory treatment for MDS, and the MDS International Prognostic Points System (IPSS) evaluates the prognosis according to the number of cytopenias, the proportion of blasts in the bone marrow and the karyotype, which is a basic tool to guide treatment, with a low risk of 0 points; Intermediate-1 (Int-1) 0.5~1 point; Intermediate-2 (Int-2) 1.5~2 points; High-risk ≥2.5 points. For low-risk or Int-1 patients, the treatment is mainly to improve the quality of life, using supportive therapy, hematopoiesis, induction differentiation and biological response modulators, while the Int-2 and high-risk MDS is mainly to improve survival, using combination chemotherapy regimen and hematopoietic stem cell transplantation.
There are 3 final outcomes of myelodysplastic syndrome: the development of leukemia, some patients enter leukemia in 2 years, and some patients can last for 10~15 years or even longer to develop leukemia; long-term myelodysplastic syndrome without developing leukemia; Some patients die from infection or bleeding from bone marrow failure before they enter leukemia.
There are also a small number of patients with myelodysplastic syndrome whose clinical symptoms disappear after treatment, and the blood picture and bone marrow image return to normal, that is, they are cured.
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