Context.—Shwachman-Diamond syndrome (SDS) is a rare inherited disorder characterized by pancreatic insufficiency, neutropenia, and in some patients, metaphyseal dysostosis. Patients with SDS are at a high risk for development of bone marrow failure, myelodysplastic syndrome, and acute leukemia. The p53 gene plays a major role in cell-cycle regulation, particularly in the presence of a genetic alteration in DNA, a critical step for the initiation of leukemogenesis. p53 gene up-regulation and p53 protein overexpression may occur as a cellular reaction to significant DNA damage. Shwachman-Diamond syndrome and refractory anemia patients have close similarities in the prevalence of acute leukemia and in cell-cycle changes in bone marrow cells. This similarity was further investigated for p53 protein overexpression using archived tissue from patients with hematologic diseases having various leukemic propensities, including SDS and refractory anemia.

Methods.—Immunohistochemical staining for p53 protein overexpression was performed on bone marrow biopsies from 9 patients with SDS. These specimens were compared with biopsies from 71 patients with acquired hematologic disorders with variable risk levels for leukemia, including acquired aplastic anemia (n = 14), refractory anemia (n = 46), and various acquired cytopenias (n = 11), as well as 37 control subjects.

Results.—p53 protein overexpression was identified only in patients with SDS and in patients with refractory anemia; these groups exhibited comparable prevalences of 78% and 72%, respectively. None of the patients with acquired aplastic anemia, acquired cytopenias, or in the control group showed overexpression of p53 protein.

Conclusion.—The prevalence of p53 protein overexpression in SDS is significantly different from that in acquired aplastic anemia and acquired cytopenias, but it is similar to the prevalence in refractory anemia. We speculate that p53 protein overexpression in this bone marrow failure syndrome may represent an early indicator of significant DNA genetic alteration, which is a crucial step in the process of leukemogenesis.