Leukopenia is More Common in MDS
In patients with Myelodysplastic Syndrome (MDS), leukopenia (low white blood cell count) is significantly more common than leukocytosis. MDS is fundamentally characterized by cytopenias—reductions in blood cell counts—not elevations 1, 2.
The Cytopenic Nature of MDS
MDS is defined by ineffective hematopoiesis leading to blood cytopenias, which include anemia, neutropenia (a form of leukopenia), and/or thrombocytopenia 1, 3. The diagnostic criteria for MDS specifically require the presence of blood cytopenias that persist over several months 1, 3.
Typical Presentation Pattern
- Anemia is the dominant cytopenia: More than 90% of MDS patients present with anemia at diagnosis 1
- Neutropenia (leukopenia) is common: Patients typically present with reduced neutrophil counts as part of the cytopenic picture 2, 4
- The bone marrow paradox: Despite peripheral cytopenias, the bone marrow is usually hypercellular or normocellular, reflecting the ineffective hematopoiesis where cells die before reaching maturity 1, 5
When Leukocytosis Occurs in MDS
Leukocytosis in MDS is the exception, not the rule, and typically indicates specific circumstances:
- Chronic myelomonocytic leukemia (CMML): This MDS/myeloproliferative overlap syndrome can present with elevated white blood cell counts 1
- Progression to acute leukemia: Excessive leukocytosis may occur when MDS transforms to acute myeloid leukemia, representing "spilling of malignant blasts into the periphery" 1
- These situations require cytoreductive therapy: When leukocytosis does occur, it may necessitate treatment with hydroxyurea or low-dose cytarabine 1
Clinical Implications
The cytopenic presentation of MDS drives the major clinical problems:
- Infection risk from neutropenia: Requires monitoring and supportive care with growth factors in some cases 1
- Bleeding risk from thrombocytopenia: Necessitates platelet transfusion support 1
- Symptomatic anemia: The most frequent problem, requiring red blood cell transfusions in many patients 1
Common Pitfall to Avoid
Do not confuse a hypercellular bone marrow with peripheral leukocytosis. MDS characteristically shows hypercellular marrow with peripheral cytopenias—this dissociation is a hallmark of the disease's ineffective hematopoiesis 1, 5. The cells are produced but die prematurely in the marrow (apoptosis) rather than maturing and entering the peripheral blood 5.