Myelodysplastic syndrome: from morphology to biology.

Myelodysplastic syndrome is characterized by ineffective hematopoiesis manifesting as peripheral cytopenia, despite adequate or increased cellularity in bone marrow. Increased intramedullary apoptosis is thought to be the mechanism underlying this phenomenon. However, the mechanisms leading to this increased apoptosis remain largely unknown. Although less apoptosis is seen in more advanced disease with increased blasts, apoptosis remains the major characteristic feature of this disease and data suggest that all cases are biologically similar, irrespective of the blast count. Myelodysplastic syndrome is a highly aggressive disease that carries a poor prognosis, especially in symptomatic patients. New therapeutic agents that target histone deacetylation, DNA methylation, or angiogenesis show promise, but focused biologic and therapeutic studies are needed to improve the outcome of this disease.