General Information About Myelodysplastic Syndromes (MDS)
Incidence and Mortality
The MDS are a collection of myeloid malignancies characterized by one or more peripheral blood cytopenias. MDS are diagnosed in slightly more than 10,000 people in the United States yearly, for an annual age-adjusted incidence rate of approximately 4.4 to 4.6 cases per 100,000 people. They are more common in men and whites. The syndromes may arise de novo or secondarily after treatment with chemotherapy and/or radiation therapy for other cancers or, rarely, after environmental exposures.
Prognosis is directly related to the number of bone marrow blast cells, to certain cytogenetic abnormalities, and to the amount of peripheral blood cytopenias. By convention, MDS are reclassified as acute myeloid leukemia (AML) with myelodysplastic features when blood or bone marrow blasts reach or exceed 20%. Many patients succumb to complications of cytopenias before progression to this stage. (Refer to the Pathologic and Prognostic Systems for Myelodysplastic Syndromes section of this summary for more information.) The acute leukemic phase is less responsive to chemotherapy than is de novo AML.
MDS are characterized by abnormal bone marrow and blood cell morphology. Megaloblastoid erythroid hyperplasia with macrocytic anemia, associated with normal vitamin B12 and folate levels, is frequently observed. Circulating granulocytes are often hypogranular or hypergranular, and may display the acquired pseudo-Pelger-Huët abnormality. Early, abnormal myeloid progenitors are identified in the marrow in varying percentages. Abnormally small megakaryocytes (micromegakaryocytes) may be seen in the marrow and hypogranular or giant platelets may appear in the blood.
MDS occur predominantly in older patients (usually those older than 60 years), with a median age at diagnosis of approximately 70 years, although patients as young as 2 years have been reported. Anemia, bleeding, easy bruising, and fatigue are common initial findings. (Refer to the PDQ summary on Fatigue for more information.) Splenomegaly or hepatosplenomegaly may indicate an overlapping myeloproliferative neoplasm. Approximately 50% of patients have a detectable cytogenetic abnormality, most commonly a deletion of all or part of chromosome 5 or 7, or trisomy 8. Single-nucleotide polymorphism array technology may increase the detection of genetic abnormalities to 80%.[4,5] Although the bone marrow is usually hypercellular at diagnosis, 10% of patients present with a hypoplastic bone marrow. Hypoplastic myelodysplastic patients tend to have profound cytopenias and may respond more frequently to immunosuppressive therapy.
Approximately 90% of MDS cases occur de novo with no identifiable cause. Potential environmental risk factors for developing MDS include exposure to the following:[7,8]
- Tobacco smoke.
- Ionizing radiation.
- Organic chemicals (e.g., benzene, toluene, xylene, and chloramphenicol).
- Heavy metals.
- Stone and cereal dusts.
- Exhaust gases.
- Nitro-organic explosives.
- Petroleum and diesel derivatives.
A PDQ summary containing information about myelodysplastic syndromes in children is:
- Ma X, Does M, Raza A, et al.: Myelodysplastic syndromes: incidence and survival in the United States. Cancer 109 (8): 1536-42, 2007. [PUBMED Abstract]
- Sekeres MA, Schoonen WM, Kantarjian H, et al.: Characteristics of US patients with myelodysplastic syndromes: results of six cross-sectional physician surveys. J Natl Cancer Inst 100 (21): 1542-51, 2008. [PUBMED Abstract]
- Tuncer MA, Pagliuca A, Hicsonmez G, et al.: Primary myelodysplastic syndrome in children: the clinical experience in 33 cases. Br J Haematol 82 (2): 347-53, 1992. [PUBMED Abstract]
- Gyger M, Infante-Rivard C, D’Angelo G, et al.: Prognostic value of clonal chromosomal abnormalities in patients with primary myelodysplastic syndromes. Am J Hematol 28 (1): 13-20, 1988. [PUBMED Abstract]
- Tiu RV, Gondek LP, O’Keefe CL, et al.: Prognostic impact of SNP array karyotyping in myelodysplastic syndromes and related myeloid malignancies. Blood 117 (17): 4552-60, 2011. [PUBMED Abstract]
- Nand S, Godwin JE: Hypoplastic myelodysplastic syndrome. Cancer 62 (5): 958-64, 1988. [PUBMED Abstract]
- Du Y, Fryzek J, Sekeres MA, et al.: Smoking and alcohol intake as risk factors for myelodysplastic syndromes (MDS). Leuk Res 34 (1): 1-5, 2010. [PUBMED Abstract]
- Strom SS, Gu Y, Gruschkus SK, et al.: Risk factors of myelodysplastic syndromes: a case-control study. Leukemia 19 (11): 1912-8, 2005. [PUBMED Abstract]