How are unclassifiable myelodysplastic syndromes (MDS-U) differentiated from other myelodysplastic syndromes (MDS)?

Updated: Jul 21, 2020
  • Author: Robert P Hasserjian, MD; Chief Editor: Christine G Roth, MD  more...
  • Print


The clinical features of unclassifiable myelodysplastic syndromes (MDS-U) cases vary depending on the specific type. Common to all myelodysplastic syndrome (MDS) cases is that patients usually present with symptoms related to one or more cytopenias.

Although the clinical features of MDS-U are varied, obtaining a detailed clinical history and complete blood cell (CBC) count with differentials is critical to exclude other, specific types of MDS that may masquerade as MDS-U. If the patient’s history includes chemotherapy or radiation therapy, the case should be classified as therapy-related MDS (t-MDS), not MDS-U. Therapy-related MDS may present with cytopenias and a cytogenetic abnormality in the absence of significant dysplasia, mimicking MDS-U if the pertinent history is not elicited. [8]

The administration of exogenous growth factors such as granulocyte colony-stimulating factor (G-CSF) may transiently increase the peripheral blast count to a level of 1% (or higher). Thus, possible effects of growth factors should be excluded before diagnosing MDS-U on the basis of 1% peripheral blasts; ideally, a peripheral smear should be examined at least 1 week off exogenous growth factors.

Finally, patients with refractory cytopenia with unilineage dysplasia (RCUD) may develop pancytopenia due to the transient effects of drugs, toxins, infection, immune processes, or metabolic derangements. The pancytopenia should be shown to be persistent and unexplained (aside from ineffective hematopoiesis due to the MDS) before a case that would otherwise qualify as refractory cytopenias with underlying dysplasia is diagnosed as MDS-U.

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!