The objective of this protocol is to determine whether leucovorin treatment can normalize hematopoietic cell growth and differentiation in patients with 5q-syndrome which may lack the gene for dihydrofolate reductase (DHFR) enzyme. The patients will be treated with oral leucovorin for 3 months and will be monitored for improvements in their counts. In addition, bone marrow colony assays will be performed in the presence and absence of leucovorin. The DHFR gene will be sequenced in each patient to screen for DHFR mutations. FISH analysis for the DHFR will also be performed on the cytogenetic material to assess the presence and copy number of the DHFR gene.
