Haema 2012; 3(2): 117-124
by Nikolaos Giannakoulas, Panagiota Matsouka
Hematology Clinic, University Medical School of Thessalia, General Hospital of Larissa
Abstract
Two distinct and relatively rare subtypes of myelodysplastic syndromes (MDS) are the hypoplastic myelodysplastic syndrome (H-MDS) and the MDS with bone marrow fibrosis (MDS-F). Pathogenesis in both subtypes is attributed mostly to the dysregulation of microenviromental cells and the secreted cytokines. H-MDS can often hardly be differentiated from AA cases. Older age, genomic instability, higher numbers of CD34 cells, cytogenetic abnormalities and worse survival are some of the characteristics that help in distinguishing between h-MDS and AA. From the pathogenetic point of view, h-MDS seem to be caused by increased apoptosis and an immune attack of myeloid progenitor cells by cytotoxic T-lymphocytes. The target-antigen might be WT1 protein or other proteinases hyper-expressed on clonal hematopoietic cells. Cellularity may not substantially affect either response to therapy or prognosis. Efficient therapy in older age is combination of antithymocyte globulin and cyclosporine although younger patients seem to benefit from stem cell transplantation. MDS-F are characterized by intermediate or severe cytopenias. The diagnosis is mainly based on bone marrow biopsy and is differentiated by primary myelofibrosis and other contitions with marrow fibrosis. The main pathology findings in MDS-F are trilineage dysplasia, dysmegacaryopoesis, bands of reticulin or collagen and clusters of CD34+ blast cells. Prognosis is poor and leukemic transformation is the usual cause of death. Therapeutic approaches are corticosteroids, anabolic compounds and supportive measures. Allogeneic stem cell transplantation is the only curative therapeutic option in younger patients.