Mounting evidence suggests that p53 plays an important role in the development and progression of the 5q- syndrome, with activation of wild-type p53 resulting in increased apoptosis and defective erythropoiesis in the early stages of the disease, followed by an expansion of a small subclone harboring mutant (inactivated) p53 in some patients as the disease progresses, leading to leukemic transformation. Here, TP53 is linked to myelodysplastic syndrome associated with isolated del(5q).