Blood Disorder Abbreviated "MD"
The blood disorder abbreviated "MD" is Myelodysplastic Syndrome (MDS), not "MG deficiency" or "MD deficiency." 1
Understanding the Terminology
MDS is a clonal hematopoietic stem cell disorder characterized by ineffective hematopoiesis, dysplasia in one or more myeloid lineages, and risk of progression to acute myeloid leukemia (AML). 1 The abbreviation "MD" appears in several MDS-related contexts:
- MD-CMML: Myelodysplastic variant of Chronic Myelomonocytic Leukemia (white blood cell count <13×10⁹/L) 1
- MDS: Myelodysplastic Syndrome (the primary disorder) 1
Key Clinical Features of MDS
Presentation:
- Over 90% of MDS patients present with anemia at diagnosis 2
- Cytopenias (anemia, thrombocytopenia, and/or neutropenia) are the hallmark features 1, 3
- Persistent cytopenias for at least 4-6 months are required for diagnosis 1
Diagnostic Criteria:
- Dysplasia in ≥10% of cells in one or more myeloid lineages 1, 3
- Blast percentage of 5-19% indicates MDS with excess blasts 3
- ≥15% ring sideroblasts indicates sideroblastic features 3, 4
- Specific cytogenetic abnormalities (del(5q), del(20q), +8, -7/del(7q)) 1
WHO Classification of MDS Subtypes
The 2016 WHO classification identifies six main MDS entities 1:
- MDS-SLD: MDS with single lineage dysplasia (includes refractory anemia, refractory neutropenia, refractory thrombocytopenia) 1
- MDS-RS: MDS with ring sideroblasts 1
- MDS with multilineage dysplasia 1
- MDS-EB: MDS with excess blasts (EB-1: <10% blasts; EB-2: 10-19% blasts) 1
- MDS with isolated del(5q) 1
- MDS-U: MDS unclassifiable 1
Common Pitfall: Distinguishing MDS from Megaloblastic Anemia
Critical distinction: MDS can present with macrocytic anemia similar to vitamin B12 or folate deficiency (megaloblastic anemia), but these are fundamentally different disorders. 5, 6, 7
- Megaloblastic anemia is reversible with vitamin supplementation 6, 8
- MDS is an irreversible clonal stem cell disorder requiring different management 8
- Both can coexist simultaneously, though this is rare 8
Key differentiating features:
- MDS typically shows dysplasia in multiple cell lines, not just erythroid precursors 9
- Cytogenetic abnormalities in MDS persist after vitamin replacement 8
- MDS carries risk of progression to AML (11-65% depending on subtype) 1
When to Suspect MDS
Bone marrow evaluation is indicated when 3:
- Unexplained persistent bicytopenia or pancytopenia after excluding reversible causes 3
- Peripheral smear shows dysplastic features 3
- Macrocytic anemia with thrombocytopenia and/or leukopenia that doesn't respond to vitamin supplementation 5, 7
Do not diagnose simple sideroblastic anemia if pancytopenia is present - this indicates MDS-U with worse prognosis and higher risk of progression to AML. 4